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1
Rybka, Marcin. "Optical properties of MAX-phase materials." Thesis, Linköping University, Applied Optics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-60008.
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<p> </p><p><p> </p></p><p><p><p> </p></p></p><p>MAX-phase materials are a new type of material class. These materials are potentiallyt echnologically important as they show unique physical properties due to the combination of metals and ceramics. In this project, spectroscopic ellipsometry in the spectral range of 0.06 eV –6.0 eV was used to probe the linear optical response of MAX-phases in terms of the complexd dielectric function <em>ε(ω) = ε1(ω) + iε2(ω<em>). </em></em>Measured data were fit to theoretical models using the Lorentz and generalized oscillator models. Data from seven different samples of MAX-phase materials were obtained using two ellipsometers. Each sample dielectric function was determined, including their infrared spectrum.</p>
2
Wunder, Daniel P. "Aerosol scattering phase function retrieval from polar orbiting satellites." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FWunder.pdf.
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Agyo, Sanfo David. "Bi-fractional transforms in phase space." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/14522.
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The displacement operator is related to the displaced parity operator through a two dimensional Fourier transform. Both operators are important operators in phase space and the trace of both with respect to the density operator gives the Wigner functions (displaced parity operator) and Weyl functions (displacement operator). The generalisation of the parity-displacement operator relationship considered here is called the bi-fractional displacement operator, O(α, β; θα, θβ). Additionally, the bi-fractional displacement operators lead to the novel concept of bi-fractional coherent states. The generalisation from Fourier transform to fractional Fourier transform can be applied to other phase space functions. The case of the Wigner-Weyl function is considered and a generalisation is given, which is called the bi-fractional Wigner functions, H(α, β; θα, θβ). Furthermore, the Q−function and P−function are also generalised to give the bi-fractional Q−functions and bi-fractional P−functions respectively. The generalisation is likewise applied to the Moyal star product and Berezin formalism for products of non-commutating operators. These are called the bi-fractional Moyal star product and bi-fractional Berezin formalism. Finally, analysis, applications and implications of these bi-fractional transforms to the Heisenberg uncertainty principle, photon statistics and future applications are discussed.
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Agyo, Sanfo D. "Bi-fractional transforms in phase space." Thesis, University of Bradford, 2016. http://hdl.handle.net/10454/14522.
Full textAbstract:
The displacement operator is related to the displaced parity operator through a two dimensional
Fourier transform. Both operators are important operators in phase space
and the trace of both with respect to the density operator gives the Wigner functions
(displaced parity operator) and Weyl functions (displacement operator). The generalisation
of the parity-displacement operator relationship considered here is called
the bi-fractional displacement operator, O(α, β; θα, θβ). Additionally, the bi-fractional
displacement operators lead to the novel concept of bi-fractional coherent states.
The generalisation from Fourier transform to fractional Fourier transform can be
applied to other phase space functions. The case of the Wigner-Weyl function is considered
and a generalisation is given, which is called the bi-fractional Wigner functions,
H(α, β; θα, θβ). Furthermore, the Q−function and P−function are also generalised to
give the bi-fractional Q−functions and bi-fractional P−functions respectively. The
generalisation is likewise applied to the Moyal star product and Berezin formalism for
products of non-commutating operators. These are called the bi-fractional Moyal star
product and bi-fractional Berezin formalism.
Finally, analysis, applications and implications of these bi-fractional transforms
to the Heisenberg uncertainty principle, photon statistics and future applications are
discussed.
5
Haraldsson, Henrik. "Assessment of Myocardial Function using Phase Based Motion Sensitive MRI." Doctoral thesis, Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-60027.
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Quantitative assessment of myocardial function is a valuable tool for clinical applications and physiological studies. This assessment can be acquired using phase based motion sensitive magnetic resonance imaging (MRI) techniques. In this thesis, the accuracy of these phase based motion sensitive MRI techniques is investigated, and modifications in acquisition and post-processing are proposed. The strain rate of the myocardium can be used to evaluate the myocardial function. However, the estimation of strain rate from the velocity data acquired with phase-contrast MRI (PC-MRI) is sensitive to noise. Estimation using normalized convolution showed, however, to reduce this sensitivity to noise and to minimize the influence of non-myocardial tissue which could impair the result. Strain of the myocardium is another measure to assess myocardial function. Strain can be estimated from the myocardial displacement acquired with displacement encoding with stimulated echo (DENSE). DENSE acquisition can be realized with several different encoding strategies. The choice of encoding scheme may make the acquisition more or less sensitive to different sources of error. Two potential sources of errors in DENSE acquisition are the influence of the FID and of the off-resonance effects. Their influence on DENSE were investigated to determine suitable encoding strategies to reduce their influence and thereby improve the measurement accuracy acquired. The quality of the DENSE measurement is not only dependent on the accuracy, but also the precision of the measurement. The precision is affected by the SNR and thereby depends on flip angle strategies, magnetic field strength and spatial variation of the receiver coil sensitivity. A mutual comparison of their influence on SNR in DENSE was therefore performed and could serve as a guideline to optimize parameters for specific applications. The acquisition time is often an important factor, especially in clinical applications where it affects potential patient discomfort and patient through-put. A multiple-slice DENSE acquisition was therefore presented, which allows the acquisition of strain values according to the 16-segment cardiac model within a single breath-hold, instead of the conventional three breath-holds. The DENSE technique can also be adapted toward comprehensive evaluation of the heart in the form of full three-dimensional three-directional acquisition of the displacement. To estimate the full strain tensor from these data, a novel post-processing technique using a polynomial was investigated. The method yielded accurate results on an analytical model and \textit{in-vivo} strains obtained agreed with previously reported myocardial strains in normal volunteers.
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Can, Geylani. "S-phase checkpoint activity and function throughout the cell cycle." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268506.
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DNA damage or replication stress during S-phase can activate the S-phase checkpoint which executes a variety of responses, such as the inhibition of origin firing and replication fork stabilisation. Deregulation of the S-phase checkpoint leads to genomic instability, which has been implicated in diseases such as cancer. In this thesis, I aimed to address whether the S-phase checkpoint is regulated outside of S-phase, and how the S-phase checkpoint targets its substrates in budding yeast. Although this checkpoint has thus far been associated exclusively with S-phase, it remains unknown whether its responses such as inhibition of origin firing can also occur in other phases of the cell cycle. To investigate this, the targets of the S-phase checkpoint for the inhibition of origin firing were analysed outside of S-phase upon DNA damage. Interestingly, I showed that the S-phase checkpoint effector kinase Rad53 phosphorylates its targets to inhibit origin firing outside of S-phase upon DNA damage when there is no replication. I then set out to test whether inhibition of origin firing by Rad53 outside of S-phase might be important for faithful DNA replication. Having shown that the checkpoint response is not specific for any cell cycle phases, I then tested how the specificity of Rad53 for its substrates might be determined. After demonstrating that the essential replication protein Cdc45 is required for Rad53 to phosphorylate the initiation factor Sld3, the key residues of Cdc45 necessary for Rad53 interaction were identified. A Cdc45 allele was produced by mutating the identified residues. This allele of Cdc45 is a separation-of-function mutant which prevents Sld3 phosphorylation upon DNA damage, but retains its function in DNA replication. Because Cdc45 travels with the replication fork, it is possible that Cdc45 also targets Rad53 to the replication fork to stabilise it upon replication stress. Overall, this thesis provides evidence that the S-phase checkpoint can function throughout the cell cycle and that Cdc45 targets Rad53 to some of its substrates, and possibly plays a role in replication fork stabilisation.
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Galanis, Andreas. "Phase transitions in the complexity of counting." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52211.
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A recent line of works established a remarkable connection for antiferromagnetic 2-spin systems, including the Ising and hard-core models, showing that the computational complexity of approximating the partition function for graphs with maximum degree \Delta undergoes a computational transition that coincides with the statistical physics uniqueness/non-uniqueness phase transition on the infinite \Delta-regular tree. Despite this clear picture for 2-spin systems, there is little known for multi-spin systems. We present the first analog of the above inapproximability results for multi-spin systems.
The main difficulty in previous inapproximability results was analyzing the behavior of the model on random \Delta-regular bipartite graphs, which served as the gadget in the reduction. To this end one needs to understand the moments of the partition function. Our key contribution is connecting: (i) induced matrix norms, (ii) maxima of the expectation of the partition function, and (iii) attractive fixed points of the associated tree recursions (belief propagation). We thus obtain a generic analysis of the Gibbs distribution of any multi-spin system on random regular bipartite graphs. We also treat in depth the k-colorings and the q-state antiferromagnetic Potts models.
Based on these findings, we prove that for \Delta constant and even k<\Delta, it is NP-hard to approximate within an exponential factor the number of k-colorings on triangle-free \Delta-regular graphs. We also prove an analogous statement for the antiferromagnetic Potts model. Our hardness results for these models complement the conjectured regime where the models are believed to have efficient approximation schemes. We systematize the approach to obtain a general theorem for the computational hardness of counting in antiferromagnetic spin systems, which we ultimately use to obtain the inapproximability results for the k-colorings and q-state antiferromagnetic Potts models, as well as (the previously known results for) antiferromagnetic 2-spin systems. The criterion captures in an appropriate way the statistical physics uniqueness phase transition on the tree.
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Konovalova, V. V., G. A. Pobigay, Y. M. Samchenko, A. F. Burban, and Z. R. Ulberg. "Nanocomposite Membranes with pH- and Thermo-sensitive Function." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35333.
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Resent researches and development in the field of membrane science are focused on improvement of synthetic membranes’ functionality. Combination of soft polymer pH- and temperature-sensitive hydrogels with rigid ultrafiltration membrane attracts much interest as a new class of smart functional systems. In this research we develop pH- and temperature-sensitive composite membranes using radical copolymerization method and study their properties depending on hydrogel composition, nature of synthetic mem-branes, temperature and pH of external medium.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35333
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Aouni, Jihane. "Utility-based optimization of phase II / phase III clinical development." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS032/document.
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Le développement majeur de la thèse a été consacré au problème d’optimisation du choix de dose dans les essais de recherche de dose, en phase II. Nous avons considéré ce problème sous l’angle des fonctions d’utilité. Nous avons alloué une valeur d’utilité aux doses, le problème pour le sponsor étant de trouver la meilleure dose, c’est-à-dire celle dont l’utilité est la plus élevée.Dans ce travail, nous nous sommes limités à une seule fonction d’utilité, intégrant deux composantes: une composante liée à l’efficacité (la POS=puissance d’un essai de phase III de 1000 patients de cette dose contre placebo) et une autre liée à la safety. Pour cette dernière, nous avons choisi de la caractériser par la probabilité prédictive d’observer un taux de toxicité inférieur ou égal à un certain seuil (que nous avons fixé à 0.15) en phase III (toujours pour un essai de 1000 patients au total). Cette approche a l’avantage d’être similaire aux concepts utilisés dans les essais de phase I en oncologie qui ont notamment pour objectif la recherche de la dose liée à une toxicité limite (notion de ”Dose limiting Toxicity”).Nous avons retenu une approche bayésienne pour l’analyse des données de la phase II.Mis à part les avantages théoriques connus de l’approche bayésienne par rapport à l’approche fréquentiste (respect du principe de vraisemblance, dépendance moins grande aux résultats asymptotiques, robustesse), nous avons choisi l’approche bayésienne pour plusieurs raisons:• Combinant, par définition même de l’approche bayésienne, une information a priori avec les données disponibles, elle offre un cadre plus flexible la prise de décision du sponsor: lui permettant notamment d’intégrer de manière plus ou moins explicite les informations dont il dispose en dehors de l’essai de la phase II.• L’approche bayésienne autorise une plus grande flexibilité dans la formalisation des règles de décision.Nous avons étudié les propriétés des règles de décisions par simulation d’essais de phase II de différentes tailles: 250, 500 et 1000 patients. Pour ces deux derniers design nous avons aussi évalué l’intérêt de d’effectuer une analyse intermédiaire lorsque la moitié des patients a été enrôlée (c’est-à-dire avec respectivement les premiers 250 et 500 patients inclus). Le but était alors d’évaluer si, pour les essais de phase II de plus grande taille, s’autoriser la possibilité de choisir la dose au milieu de l’étude et de poursuivre l’étude jusqu’au bout si l’analyse intermédiaire n’est pas concluante permettait de réduire la taille de l’essai de phase II tout en préservant la pertinence du choix de dose final<br>The main development of the thesis was devoted to the problem of dose choice optimization in dose-finding trials, in phase II. We have considered this problem from the perspective of utility functions. We have allocated a utility value to the doses itself, knowing that the sponsor’s problem was now to find the best dose, that is to say, the one having the highest utility. We have limited ourselves to a single utility function, integrating two components: an efficacy-related component (the PoS = the power of a phase III trial - with 1000 patients - of this dose versus placebo) and a safety-related component. For the latter, we chose to characterize it by the predictive probability of observing a toxicity rate lower or equal to a given threshold (that we set to 0.15) in phase III (still for a trial of 1000 patients in total). This approach has the advantage of being similar to the concepts used in phase I trials in Oncology, which particularly aim to find the dose related to a limiting toxicity (notion of "Dose limiting Toxicity").We have adopted a Bayesian approach for the analysis of phase II data. Apart from the known theoretical advantages of the Bayesian approach compared with the frequentist approach (respect of the likelihood principle, less dependency on asymptotic results, robustness), we chose this approach for several reasons:• It provides a more flexible framework for the decision-making of the sponsor because it offers the possibility to combine (by definition of the Bayesian approach) a priori information with the available data: in particular, it offers the possibility to integrate, more or less explicitly, the information available outside the phase II trial.• The Bayesian approach allows greater flexibility in the formalization of the decision rules.We studied the properties of decision rules by simulating phase II trials of different sizes: 250, 500 and 1000 patients. For the last two designs (500 and 1000 patients in phase II), we have also evaluated the interest of performing an interim analysis when half of the patients are enrolled (i.e. with the first 250and the first 500 patients included respectively). The purpose was then to evaluate whether or not, for larger phase II trials, allowing the possibility of choosing the dose in the middle of the study and continuing the study to the end if the interim analysis is not conclusive, could reduce the size of the phase II trial while preserving the relevance of the final dose choice
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Engblom, Johan. "On the phase behaviour of lipids with respect to skin barrier function." Lund, Sweden : Dept. of Food Technology, Lund University, 1996. http://books.google.com/books?id=TdFqAAAAMAAJ.
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Mentlak, Thomas Andrew. "Investigating LysM effector function and the biotrophic growth phase of Magnaporthe oryzae." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3870.
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During intracellular biotrophic growth, the rice blast fungus Magnaporthe oryzae secretes a large battery of effector proteins, which are thought to suppress host cell defence responses. Although a number of these effector proteins have been identified, their precise biological functions and contribution towards plant infection remains unclear. In this thesis, I report that during biotrophic growth, the secretion of a LysM effector protein, Slp1, is required for rice blast disease. I show that Slp1 binds chitin and is able to suppress the chitin-induced oxidative burst and defence gene-expression in rice cells. Slp1 competes with the membrane-localised chitin receptor CEBiP in rice, and this competitive interaction results in a reduction in virulence associated with Δslp1 null mutants. Slp1 is secreted by intracellular hyphae specifically during biotrophic growth, and accumulates around hyphal tips at the plant-fungal interface. Using transgenic rice lines which express fluorescent marker proteins targeted to the plasma membrane and endoplasmic reticulum, I investigate the biotrophic growth phase of M. oryzae. I show that the rice host plasma membrane becomes tightly apposed to invasive biotrophic intracellular hyphae. I also show that the rice host plasma membrane and endoplasmic reticulum accumulate around the Biotrophic Interfacial Complex (BIC), a bulbous structure attached to the sub-apical region of intracellular fungal hyphae, which accumulates fluorescently-labelled avirulence effector proteins. Using a fungal plasma membrane marker, I show that the BIC resides outside the fungal plasma membrane and cell wall is made exclusively of plant cellular material.
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Farquharson, Maree Louise. "Estimating the parameters of polynomial phase signals." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16312/1/Maree_Farquharson_Thesis.pdf.
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Nonstationary signals are common in many environments such as radar, sonar, bioengineering and power systems. The nonstationary nature of the signals found in these environments means that classicalspectralanalysis techniques are notappropriate for estimating the parameters of these signals. Therefore it is important to develop techniques that can accommodate nonstationary signals. This thesis seeks to achieve this by firstly, modelling each component of the signal as having a polynomial phase and by secondly, developing techniques for estimating the parameters of these components.
Several approaches can be used for estimating the parameters of polynomial phase signals, eachwithvarying degrees ofsuccess.Criteria to consider in potential estimation algorithms are
(i) the signal-to-noise (SNR) ratio threshold of the algorithm, (ii) the amount of computation required for running the algorithm, and (iii) the closeness of the resulting estimates' mean-square errors to the minimum theoretical bound. These criteria will be used to compare the new techniques developed in this thesis with existing techniques.
The literature on polynomial phase signal estimation highlights the recurring trade-off between the accuracy of the estimates and the amount of computation required. For example, the Maximum Likelihood (ML) method provides near-optimal estimates above threshold, but also incurs a heavy computational cost for higher order phase signals. On the other hand, multi-linear techniques such as the high-order ambiguity function (HAF) method require little computation, but have a significantly higher SNR threshold than the ML method.
Of the existing techniques, the cubic phase (CP) function method is a promising technique because it provides an attractive SNR threshold and computational complexity trade-off. For this reason, the analysis techniques developed in this thesis will be derived from the CP function.
A limitation of the CP function is its inability to accurately process phase orders greater than three. Therefore, the first novel contribution to this thesis develops a broadened class of discrete-time higher order phase (HP)functions to address this limitation.This broadened class is achieved by providing a multi-linear extension of the CP function. Monte Carlo simulations are performed to demonstrate the statistical advantage of the HP functions compared to the HAFs. A first order statistical analysis of the HP functions is presented. This analysis verifies the simulation results.
The next novel contribution is a technique called the lower SNR cubic phase function (LCPF)method. It is an extension of the CP function, with the extension enabling performance at lower signal-to-noise ratios (SNRs). The improvement of the SNR threshold's performance is achieved by coherently integrating the CP function over a compact interval in the two-dimensional CP function space. The computation of the new algorithm is quite moderate, especially when compared to the ML method. Above threshold, the LCPF method's parameter estimates are asymptotically efficient. Monte Carlo simulation results are presented and a threshold analysis of the algorithm closely predicts the thresholds observed in these results.
The next original contribution to this research involves extending the LCPF method so that it is able to process multicomponent cubic phase signals and higher order phase signals. The LCPF method is extended to higher orders by applying a windowing technique as opposed to adjusting the order of the kernel as implemented in the HP function method. To demonstrate the extension of the LCPF method for processing higher order phase signals and multicomponent cubic phase signals, some Monte Carlo simulations are presented.
Finally, these estimation techniques are applied to real-worldscenarios in the fields of Power Systems Analysis, Neuroethology and Speech Analysis.
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Farquharson, Maree Louise. "Estimating the parameters of polynomial phase signals." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16312/.
Full textAbstract:
Nonstationary signals are common in many environments such as radar, sonar, bioengineering and power systems. The nonstationary nature of the signals found in these environments means that classicalspectralanalysis techniques are notappropriate for estimating the parameters of these signals. Therefore it is important to develop techniques that can accommodate nonstationary signals. This thesis seeks to achieve this by firstly, modelling each component of the signal as having a polynomial phase and by secondly, developing techniques for estimating the parameters of these components. Several approaches can be used for estimating the parameters of polynomial phase signals, eachwithvarying degrees ofsuccess.Criteria to consider in potential estimation algorithms are (i) the signal-to-noise (SNR) ratio threshold of the algorithm, (ii) the amount of computation required for running the algorithm, and (iii) the closeness of the resulting estimates' mean-square errors to the minimum theoretical bound. These criteria will be used to compare the new techniques developed in this thesis with existing techniques. The literature on polynomial phase signal estimation highlights the recurring trade-off between the accuracy of the estimates and the amount of computation required. For example, the Maximum Likelihood (ML) method provides near-optimal estimates above threshold, but also incurs a heavy computational cost for higher order phase signals. On the other hand, multi-linear techniques such as the high-order ambiguity function (HAF) method require little computation, but have a significantly higher SNR threshold than the ML method. Of the existing techniques, the cubic phase (CP) function method is a promising technique because it provides an attractive SNR threshold and computational complexity trade-off. For this reason, the analysis techniques developed in this thesis will be derived from the CP function. A limitation of the CP function is its inability to accurately process phase orders greater than three. Therefore, the first novel contribution to this thesis develops a broadened class of discrete-time higher order phase (HP)functions to address this limitation.This broadened class is achieved by providing a multi-linear extension of the CP function. Monte Carlo simulations are performed to demonstrate the statistical advantage of the HP functions compared to the HAFs. A first order statistical analysis of the HP functions is presented. This analysis verifies the simulation results. The next novel contribution is a technique called the lower SNR cubic phase function (LCPF)method. It is an extension of the CP function, with the extension enabling performance at lower signal-to-noise ratios (SNRs). The improvement of the SNR threshold's performance is achieved by coherently integrating the CP function over a compact interval in the two-dimensional CP function space. The computation of the new algorithm is quite moderate, especially when compared to the ML method. Above threshold, the LCPF method's parameter estimates are asymptotically efficient. Monte Carlo simulation results are presented and a threshold analysis of the algorithm closely predicts the thresholds observed in these results. The next original contribution to this research involves extending the LCPF method so that it is able to process multicomponent cubic phase signals and higher order phase signals. The LCPF method is extended to higher orders by applying a windowing technique as opposed to adjusting the order of the kernel as implemented in the HP function method. To demonstrate the extension of the LCPF method for processing higher order phase signals and multicomponent cubic phase signals, some Monte Carlo simulations are presented. Finally, these estimation techniques are applied to real-worldscenarios in the fields of Power Systems Analysis, Neuroethology and Speech Analysis.
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Freund, Robert M. "A Potential Reduction Algorithm With User-Specified Phase I - Phase II Balance, for Solving a Linear Program from an Infeasible Warm Start." Massachusetts Institute of Technology, Operations Research Center, 1991. http://hdl.handle.net/1721.1/5409.
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This paper develops a potential reduction algorithm for solving a linear-programming problem directly from a "warm start" initial point that is neither feasible nor optimal. The algorithm is of an "interior point" variety that seeks to reduce a single potential function which simultaneously coerces feasibility improvement (Phase I) and objective value improvement (Phase II). The key feature of the algorithm is the ability to specify beforehand the desired balance between infeasibility and nonoptimality in the following sense. Given a prespecified balancing parameter /3 > 0, the algorithm maintains the following Phase I - Phase II "/3-balancing constraint" throughout: (cTx- Z*) < /3TX, where cTx is the objective function, z* is the (unknown) optimal objective value of the linear program, and Tx measures the infeasibility of the current iterate x. This balancing constraint can be used to either emphasize rapid attainment of feasibility (set large) at the possible expense of good objective function values or to emphasize rapid attainment of good objective values (set /3 small) at the possible expense of a lower infeasibility gap. The algorithm exhibits the following advantageous features: (i) the iterate solutions monotonically decrease the infeasibility measure, (ii) the iterate solutions satisy the /3-balancing constraint, (iii) the iterate solutions achieve constant improvement in both Phase I and Phase II in O(n) iterations, (iv) there is always a possibility of finite termination of the Phase I problem, and (v) the algorithm is amenable to acceleration via linesearch of the potential function.
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Mellechervu, Karthik. "Modeling of Transient Thrust of a Two Phase Propellant Tank." Cleveland State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1231561130.
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Higgins, Johanne. "Correlates of recovery of upper extremity function in the acute phase post stroke." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0027/MQ50786.pdf.
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Milet, Sylvain F. "Visualization and quanification of early diastolic function by magnetic resonance phase velocity mapping." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/16109.
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Scahill, David. "The South Stoa at Corinth : design, construction and function of the Greek phase." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558903.
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The focus of this dissertation is the design, construction and function of the South Stoa at Corinth in its initial phase. The South Stoa was first published in a monograph by Oscar Broneer in 1954.1 In addition to dealing with the Greek and Roman phases of the building, Broneer’s study also dealt with the “pre-stoa” remains. Certain aspects of the architecture of the stoa, however, were either treated only briefly or were entirely left out of the publication. While it was one of the first attempts at a full study of a secular Greek building, several conclusions deserve re-evaluation, including the date of construction and the design of the building in its initial phase, which has an impact on subsequent phases of remodeling, the function of the building, as well as its place in the historical development of stoas. Re-evaluation of the in situ remains of the stoa combined with newly identified architectural fragments of the building, particularly from the superstructure, provide important evidence to suggest an alternative reconstruction to that previously put forward. This new reconstruction is presented as the most likely solution, in awareness of the possibility that future finds may give rise to modification. As will be shown, the staircases inside the first and last front rooms of the stoa do not belong to the initial building phase as previously thought, but instead date to the Roman period, while evidence in the form of foundations and cuttings for a staircase inside the colonnade at the west end of the stoa, dated prior to 146 B.C., belongs to the initial phase of the building and calls for an entirely different interior reconstruction. The date of the stoa, which has fluctuated from sometime after the middle of the fourth century B.C. (340-320 B.C.) to the early decades of the third century B.C., can now be more precisely determined in view of recent examination of pottery deposits from beneath the stoa terrace, which was built prior to the stoa’s construction. These deposits have been dated between 300-290 B.C., which would push the date of the stoa’s construction to the beginning decades of the third century B.C. This has considerable bearing on the early development of Hellenistic stoas and on the stylistic chronology of several other buildings built around the end of the fourth century B.C. Having resolved aspects of the reconstruction and situated the stoa chronologically, the focus of this study moves on to design considerations, including examination of the proportions and of the ancient foot unit used in the design of the building. Construction and statics of the building are also considered.
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De, Oliveira Dominic. "Phase and structural changes of nickel catalysts as a function of reaction conditions." Master's thesis, Faculty of Engineering and the Built Environment, 2019. http://hdl.handle.net/11427/31520.
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Carbon dioxide hydrogenation is a route for the production of methane from hydrogen and carbon dioxide, which has attracted increased attention in recent times. It provides a means for both energy storage through substitute natural gas (SNG) production and as a process for the conversion of carbon dioxide into valuable products. Ni is the most widely used metal for SNG production due to its high activity, high selectivity towards methane and low cost in comparison to the other active metals. Ni catalysts have been extensively studied due to their uses in steam reforming and CO methanation, and it is known that deactivation by sintering, sulphur poisoning and carbon formation are the most common deactivation mechanisms for Ni catalysts. Some deactivation of Ni by oxidation has been reported, despite the fact the oxidation of Ni to NiO is not thermodynamically feasible at reaction conditions relevant to Ni catalysts. This has also been observed with Co catalysts for Fischer-Tropsch synthesis applications, where it has been explained that the size dependent oxidation, by produced water, can occur due to the higher surface energy contributions of smaller crystallites. The aim of this project is to study the phase changes of nickel catalysts, specifically through the oxidation of Ni in the presence of steam using in situ magnetic techniques to identify the loss of metallic Ni. As this oxidation is thought to be a size dependent effect, a set of catalysts with narrow crystallite size distributions and tuneable size is required for the experimental testing. The use of organometallic precursor reduction (OPR) and homogeneous deposition precipitation (HDP) was investigated for the synthesis in this study. OPR produced unsupported nanoparticles with a suitable size, however the occurrence of sintering during the anchoring and supporting of these nanoparticles on silica spheres, due to the high temperature calcination step, made these catalysts unsuitable for use in the oxidation study. The catalysts synthesised by HDP produced supported nickel catalysts with high loadings and sizes of 3.6 and 7.5 nm, with minimal overlap of size distributions, making them suitable for oxidation testing. The size of these nanoparticles was controlled by varying the reduction temperature. The HDP catalysts were tested at model conditions (i.e. in the absence of CO2) where the partial pressure ratios of steam to hydrogen, simulating different conversion levels, were increased up to a steam to hydrogen ratio of 400, to determine at what ratio the catalysts would begin to oxidise. The smaller catalysts showed significant oxidation at lower partial pressure ratios and to a greater extent than the larger particle size. These results showed the size dependence of the oxidation, with the large particles showing greater resistance to oxidation. These results were compared to iii thermodynamic calculations made for the size dependent oxidation of Ni, and good agreement between the experimental and predicted results was observed. The use of magnetic characterisation of the particle size was conducted by application of the Langevin equation as well as by a dispersion measurement, carried out by the titration of the Ni surface with H2. These in situ characterisation techniques showed consistency with the conventional external characterisation techniques and also showed that no size changes occurred throughout the testing, indicating that the results are truly due to size effects. Upon re-reduction of the oxidised catalysts, the full recovery of oxidised Ni was achieved with the large sample, whereas the smaller sample only achieved 60 % recovery of oxidised material. This is thought to be due to the formation of a less reducible phase, specifically metal-support compounds such as nickel silicate.
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Rahmat, Sarah Binti. "Development of a fast method for the psychophysical estimation of nonlinear cochlear function using schroeder-phase masking." Thesis, University of Canterbury. Communication Disorders, 2015. http://hdl.handle.net/10092/11268.
Full textAbstract:
In many previous physiological and psychoacoustic studies, Schroeder-phase masking (using Schroeder harmonic complexes to mask other sounds) has proven useful in understanding different aspects of cochlear function, particularly the phase curvature of the cochlea and cochlear nonlinearity. The common method of measuring Schroeder-phase masking functions uses a very time consuming three-alternative forced choice (3AFC) process, which limits its research and clinical usefulness. This thesis describes a fast method for measuring Schroeder-phase masking functions that we developed to address this problem. By adapting the Békésy tracking technique, we demonstrate how the measurement time can be reliably shortened by almost 80% in comparison to the commonly-used method. Using the fast method, we have demonstrated that the difference in masking effectiveness produced by different phases of Schroeder maskers (known as the ‘phase effect’) is reduced in conditions where cochlear non-linearity is expected to be reduced (i.e. at low intensity levels and in sensorineural hearing loss subjects) – findings which are consistent with previous studies. The possible involvement of other mechanisms in producing the Schroeder phase effect (particularly the medial olivocochlear (MOC) reflex) is discussed. Given the shorter testing time and higher resolution data it can give, the fast method can be a useful tool in estimating cochlear phase curvature. The reduction in testing time in particular may significantly aid the investigation of different aspects of cochlear function which might have been limited by the long testing time given by the commonly-used method.
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Hadhrami, Hilal Al. "Phase space methods in finite quantum systems." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4250.
Full textAbstract:
Quantum systems with finite Hilbert space where position x and momentum p take values in Z(d) (integers modulo d) are considered. Symplectic tranformations S(2ξ,Z(p)) in ξ-partite finite quantum systems are studied and constructed explicitly. Examples of applying such simple method is given for the case of bi-partite and tri-partite systems. The quantum correlations between the sub-systems after applying these transformations are discussed and quantified using various methods. An extended phase-space x-p-X-P where X, P ε Z(d) are position increment and momentum increment, is introduced. In this phase space the extended Wigner and Weyl functions are defined and their marginal properties are studied. The fourth order interference in the extended phase space is studied and verified using the extended Wigner function. It is seen that for both pure and mixed states the fourth order interference can be obtained.
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George-Reichley, Debra G. "Potential muscle function during the swing phase of stroke gait an induced acceleration study /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 51 p, 2008. http://proquest.umi.com/pqdweb?did=1481669451&sid=10&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Marklund, Sandra. "Feasibility Study of Phase Measurements of the Arterial Input Function in Dynamic Contrast Enhanced MRI." Thesis, Umeå University, Radiation Physics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-23226.
Full textAbstract:
<p> </p><p>Acquired data from dynamic contrast enhanced MRI measurements can be used to non-invasively assess tumour vascular characteristics through pharmacokinetic modelling. The modelling requires an arterial input function which is the concentration of contrast agent in the blood reaching the volume of interest as a function of time. The aim of this work is testing and optimizing a turboFLASH sequence to appraise its suitability for measuring the arterial input function by measuring phase.</p><p>Contrast concentration measurements in a phantom were done with both phase and relaxivity techniques. The results were compared to simulations of the experiment conditions to compare the conformance. The results using the phase technique were promising, and the method was carried on to in-vivo testing. The in-vivo data displayed a large signal loss which motivated a new phantom experiment to examine the cause of this signal reduction. Dynamic measurements were made in a phantom with pulsatile flow to mimic a blood vessel with a somewhat modified turboFLASH sequence. The conclusions drawn from analyzing the data were used to further improve the sequence and this modified turboFLASH sequence was tested in an in-vivo experiment. The obtained concentration curve showed significant improvement and was deemed to be a good representation of the true blood concentration.</p><p>The conclusion is that phase measurements can be recommended over relaxivity based measurements. This recommendation holds for using a slice selective saturation recovery turboFLASH sequence and measuring the arterial input function in the neck. Other areas of application need more thorough testing.</p><p> </p>
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Sarafraz, Yazdi Hossein. "Fractional Fourier transform and its optical applications." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/992.
Full textAbstract:
A definition of fractional Fourier transform as the generalization of ordinary Fourier transform is given at the beginning. Then due to optical reasons the fractional transform of a so-called chirp functions is considered in both theory and practical simulations. Because of a quadratic phase factor which is common in the definition of the transform and some optical concepts, a comparison between these concepts such as Fresnel diffraction, spherical wave, thin lens and free space propagation and the transform has been done. Finally an optical setup for performing the fractional transform is introduced.
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Cankaya, Erkan. "Use Of The Ambiguity Function Technique For Target Detection In Phase Coded Continuous Wave Radars." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606767/index.pdf.
Full textAbstract:
The goal of this thesis study is to investigate the Ambiguity Function Technique for
target detection in phase-coded continuous wave radar. Also, phase shift keying
techniques are examined in detail.
Continuous Wave (CW) Radars, which are also known as Low Probability of
Intercept (LPI) radars, emit continuous signals in time which are modulated by
either frequency modulation or phase modulation techniques. Modulation of the
transmitted radar signal is needed to estimate both the range and the radial velocity
of the detected targets. In this thesis, Phase Shift Keying (PSK) techniques such as
the Barker codes, Frank codes, P1, P2, P3, P4 codes will be employed for radar
signal modulation. The use of Ambiguity Function, which is a non-linear Time-
Frequency Representation (TFR), for target detection will be investigated in phasecoded
CW radars for different target scenarios.
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Webber, Michael L. "Phase Shift Control: Application and Performance Limitations With Respect to Thermoacoustic Instabilities." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/36418.
Full textAbstract:
<p> Lean premixed fuel-air conditions in large gas turbines are used to improve efficiency and reduce emissions. These conditions give rise to large undamped pressure oscillations at the combustor's natural frequencies which reduce the turbine's longevity and reliability. Active control of the pressure oscillations, called thermoacoustic instabilities, has been sought as passive abatement of these instabilities does not provide adequate damping and is often impractical on a large scale. Phase shift control of the instabilities is perhaps the simplest and most popular technique employed but often does not provide good performance in that controller induced secondary instabilities are generated with increasing loop gain.
</p><p>
This thesis investigates the general underlying cause of the secondary instabilities and shows that high average group delay through the frequency region of the instability is the root of the problem. This average group delay is then shown to be due not only the controller itself but can also be associated with other components and inherent characteristics of the control loop such as actuators and time delay, respectively. An "optimum" phase shift controller, consisting of an appropriate shift in phase and a low order, wide bandwidth bandpass filter, is developed for a Rijke tube combustor and shown to closely match the response of an LQG controller designed only for system
stabilization. Both the optimal phase shifter and the LQG controller are developed based on a modified model of the thermoacoustic loop which takes into account the change in density of the combustion reactants at the flame location. Additionally, the system model is coupled with a model of the control loop and then validated by comparison of simulated results to experimental results using nearly identical controllers. </p><br>Master of Science
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Sargent, Eva Lee. "The effects of intraluteal infusion of prostaglandin-synthesis inhibitors on the function of the primate corpus luteum." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184406.
Full textAbstract:
Exogenous prostaglandins (PGs) have been reported to suppress or to promote the function of the primate corpus luteum in vitro and in vivo, but the role of endogenous ovarian prostaglandins in regulating luteal function during the menstrual cycle is unknown. Infusion (via osmotic pump) of the prostaglandin-synthesis inhibitor sodium meclofenamate into the corpus luteum, but not via the jugular vein, during the midluteal phase of the menstrual cycle resulted in a decline in progesterone levels and premature menses in rhesus monkeys (Macaca mulatta). These results suggest that meclofenamate suppresses the production of an obligatory luteotropic prostaglandin or other metabolite of arachidonic acid. We were unable to confirm that ovarian prostaglandin synthesis was diminished during treatment, since we could not consistently measure a gradient in PGE or PGF₂(α) across the ovary. Dispersed cells from the macaque corpus luteum produced PGF₂(α) in vitro. Production was stimulated by exposure to arachidonic acid and was inhibited by meclofenamate and another prostaglandin-synthesis inhibitor, flurbiprofen. Although the two drugs were potent inhibitors of prostaglandin synthesis in vitro, intraluteal infusion of flurbiprofen in monkeys did not mimic the luteolytic effects of meclofenamate. These studies provide the first evidence of an obligatory luteotropic role for a metabolite of arachidonic acid during the primate luteal phase. However the data suggest that the luteolytic effect of meclofenamate in vivo is not mediated entirely by the inhibition of local prostaglandin synthesis. Further studies are needed to determine the mechanism(s) of meclofenamate-induced luteolysis and to identify the putative obligatory luteotropin.
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Vine, David John. "New quantitative methods in analyser-based phase contrast X-ray imaging." Monash University. Faculty of Science. School of Physics, 2008. http://arrow.monash.edu.au/hdl/1959.1/57830.
Full textAbstract:
New quantitative methods are developed for analyser-based phase contrast imaging (ABI) with hard X-rays. In the first instance we show that quantitative ABI may be implemented using an extended incoherent source. Next, we outline how complex Green’s functions may be reconstructed from phase contrast images and we apply this method to reconstruct the thick perfect crystal Green’s function associated with an ABI imaging system. The use of quantitative ABI with incoherent X-ray sources is not widespread and the first set of results pertains to the feasibility of quantitative ABI imaging and phase retrieval using a rotating anode X-ray source. The necessary conditions for observation of ABI phase contrast are deduced from elementary coherence considerations and numerical simulations. We then focus on the problem of extracting quantitative information from ABI images recorded using an extended incoherent X-ray source. The results of an experiment performed at Friedrich-Schiller University, Germany using a rotating anode X-ray source demonstrate the validity of our approach. It is shown that quantitative information may be extracted from such images under quite general and practicable conditions. We then develop a new use for phase contrast imaging systems that allows the Green’s function associated with a linear shift-invariant imaging system to be deduced from two phase contrast images of a known weak object. This new approach is applied to X-ray crystallography where the development of efficient methods of inferring the phase of rocking curves is an important open problem. We show how the complex Green’s function describing Bragg reflection of a coherent scalar X-ray wavefield from a crystal may be recovered from a single image over a wide range of reciprocal space simultaneously. The solution we derive is fast, non-iterative and deterministic. When applied to crystalline structures for which the kinematic scattering approximation is valid, such as thin crystalline films, our technique is shown to solve the famous one-dimensional phase retrieval problem which allows us to directly invert the Green’s function to retrieve the depth-dependent interplanar spacing. Finally we implement our Green’s function retrieval method on experimental data collected at the SPring-8 synchrotron in Hyogo, Japan. In the experiment we recorded analyser-based phase contrast images of a known weak object using a thick perfect silicon analyser crystal. It is then demonstrated that these measurements can be inverted to recover the complex Green’s function associated with the analyser crystal Bragg peak. The reconstructed Green’s function is found to be in good agreement with the prediction of dynamical diffraction theory.
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内藤, 尚., Hisashi NAITO, 雄嗣 松崎, Yuji MATSUZAKI, 忠繁 池田, Tadashige IKEDA, 敏幸 佐々木 та Toshiyuki SASAKI. "繰返し荷重を加えたTiNi形状記憶合金ワイヤの応力ーひずみー温度関係の計測および数値解析". 日本機械学会, 2003. http://hdl.handle.net/2237/9074.
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Arnison, Matthew Raphael. "Phase control and measurement in digital microscopy." Thesis, The University of Sydney, 2003. http://hdl.handle.net/2123/569.
Full textAbstract:
The ongoing merger of the digital and optical components of the modern microscope is creating opportunities for new measurement techniques, along with new challenges for optical modelling. This thesis investigates several such opportunities and challenges which are particularly relevant to biomedical imaging. Fourier optics is used throughout the thesis as the underlying conceptual model, with a particular emphasis on three--dimensional Fourier optics. A new challenge for optical modelling provided by digital microscopy is the relaxation of traditional symmetry constraints on optical design. An extension of optical transfer function theory to deal with arbitrary lens pupil functions is presented in this thesis. This is used to chart the 3D vectorial structure of the spatial frequency spectrum of the intensity in the focal region of a high aperture lens when illuminated by linearly polarised beam. Wavefront coding has been used successfully in paraxial imaging systems to extend the depth of field. This is achieved by controlling the pupil phase with a cubic phase mask, and thereby balancing optical behaviour with digital processing. In this thesis I present a high aperture vectorial model for focusing with a cubic phase mask, and compare it with results calculated using the paraxial approximation. The effect of a refractive index change is also explored. High aperture measurements of the point spread function are reported, along with experimental confirmation of high aperture extended depth of field imaging of a biological specimen. Differential interference contrast is a popular method for imaging phase changes in otherwise transparent biological specimens. In this thesis I report on a new isotropic algorithm for retrieving the phase from differential interference contrast images of the phase gradient, using phase shifting, two directions of shear, and non--iterative Fourier phase integration incorporating a modified spiral phase transform. This method does not assume that the specimen has a constant amplitude. A simulation is presented which demonstrates good agreement between the retrieved phase and the phase of the simulated object, with excellent immunity to imaging noise.
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Persson, Örjan. "General stress proteins : novel function and signals for induction of stationary phase genes in E. coli /." Göteborg : Department of Cell and Molecular Biology, University of Gothenburg, 2010. http://hdl.handle.net/2077/22213.
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Ramirez, Suarez Oscar Leonardo. "The effective-range function in nuclear physics: a method to parameterize phase shifts and extract ANCs." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209157.
Full textAbstract:
The connection between phase shifts and the ANC has been explored in the frame of the effective range theory. The main result is that, in practice and under rather simple requirements, scattering states (phases shifts) can be correctly described and connected with bound states via the effective range function, and therefore, ANCs can be accurately determined thanks to the analytic properties of this function. This result has an important impact in stellar evolution due to the ANC and phases shifts are directly connected with capture cross sections which, for instance, determine partially the stage and evolution of stars.<p><p>As a first step, the effective range function is approximated via the effective range expansion which shows that a successful phase-shift description depends on how precise the effective range parameters are determined. Thus, a technique to compute accurately these parameters is developed here. Its construction is based on a set of recurrence relations at low energy, that allows a compact and general description of the truncated<p>effective range expansion. Several potential models are used to illustrate the effectiveness<p>of this technique and to discuss its numerical limitations. The results shows that a very good precision of the effective-range parameters can be achieved; nevertheless, to describe experimental phase shifts several effective-range parameters can be needed, which shows a limitation for practical applications.<p><p>As a second step, the effective range function is analyzed theoretically in an arbitrary energy range. This analysis shows that this function can be decomposed in such a way that contributions of bound states, resonances and background can be separated in a similar way as in the phenomenological R-matrix. In this new form experimental data can be better fitted because the free parameter space is reduced considerably,<p>and therefore, extrapolations are better handled. By construction, the method agrees with the scattering matrix properties which allows a simple calculation of resonances (locations and widths) and asymptotic normalization constants (ANCs). Several tests are successfully performed via potential models. Phase shifts for the 2 + partial wave of the 12C+α are analyzed with this method. They are correctly described including both<p>resonances at Ec.m. = 2.7 and 4.4 MeV. For the 6.92 MeV (2+) exited state of 16O, the ANC estimation 112(8) × 10 3 fm^−1/2 is obtained taking into account statistical errors.<br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
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Arnison, Matthew Raphael. "Phase control and measurement in digital microscopy." University of Sydney. Physics, 2003. http://hdl.handle.net/2123/569.
Full textAbstract:
The ongoing merger of the digital and optical components of the modern microscope is creating opportunities for new measurement techniques, along with new challenges for optical modelling. This thesis investigates several such opportunities and challenges which are particularly relevant to biomedical imaging. Fourier optics is used throughout the thesis as the underlying conceptual model, with a particular emphasis on three--dimensional Fourier optics. A new challenge for optical modelling provided by digital microscopy is the relaxation of traditional symmetry constraints on optical design. An extension of optical transfer function theory to deal with arbitrary lens pupil functions is presented in this thesis. This is used to chart the 3D vectorial structure of the spatial frequency spectrum of the intensity in the focal region of a high aperture lens when illuminated by linearly polarised beam. Wavefront coding has been used successfully in paraxial imaging systems to extend the depth of field. This is achieved by controlling the pupil phase with a cubic phase mask, and thereby balancing optical behaviour with digital processing. In this thesis I present a high aperture vectorial model for focusing with a cubic phase mask, and compare it with results calculated using the paraxial approximation. The effect of a refractive index change is also explored. High aperture measurements of the point spread function are reported, along with experimental confirmation of high aperture extended depth of field imaging of a biological specimen. Differential interference contrast is a popular method for imaging phase changes in otherwise transparent biological specimens. In this thesis I report on a new isotropic algorithm for retrieving the phase from differential interference contrast images of the phase gradient, using phase shifting, two directions of shear, and non--iterative Fourier phase integration incorporating a modified spiral phase transform. This method does not assume that the specimen has a constant amplitude. A simulation is presented which demonstrates good agreement between the retrieved phase and the phase of the simulated object, with excellent immunity to imaging noise.
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Жаба, В. І. "Асимптотики фазової і хвильової функцій по методу фазових функцій". Thesis, Сумський державний університет, 2016. http://essuir.sumdu.edu.ua/handle/123456789/45793.
Full textAbstract:
Для одноканального нуклон-нуклонного розсіяння розглянуто
асимптотики фазової і хвильової функції по методу фазових функцій.
Оскілки нам відомі асимптотики для фазової функції, то їх
можна використати для запису асимптотики хвильової функції
поблизу початку координат.
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Zhou, Jing. "Experimental study of phase separation in Fe-Cr based alloys." Licentiate thesis, KTH, Metallografi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119230.
Full textAbstract:
Duplex stainless steels (DSSs) are important engineering materials due to their combination of good mechanical properties and corrosion resistance. However, as a consequence of their ferrite content, DSSs are sensitive to the so-called ‘475°C embrittlement’, which is induced by phase separation, namely, the ferrite decomposed into Fe-rich ferrite (α) and Cr-rich ferrite (α'), respectively. The phase separation is accompanied with a severe loss of toughness. Thus, the ‘475°C embrittlement’ phenomenon limits DSSs’ upper service temperature to around 250°C. In the present work, Fe-Cr binary model alloys and commercial DSSs from weldments were investigated for the study of phase separation in ferrite. Different techniques were employed to study the phase separation in model alloys and commercial DSSs, including atom probe tomography, transmission electron microscopy and micro-hardness test. Three different model alloys, Fe-25Cr, Fe-30Cr and Fe-35Cr (wt. %) were analyzed by atom probe tomography after different aging times. A new method based on radial distribution function was developed to evaluate the wavelength and amplitude of phase separation in these Fe-Cr binary alloys. The results were compared with the wavelengths obtained from 1D auto-correlation function and amplitudes from Langer-Bar-On-Miller method. It was found that the wavelengths from 1D auto-correlation function cannot reflect the 3D nano-scaled structures as accurate as those obtained by radial distribution function. Furthermore, the Langer-Bar-On-Miller method underestimates the amplitudes of phase separation. Commercial DSSs of SAF2205, 2304, 2507 and 25.10.4L were employed to investigate the connections between phase separation and mechanical properties from different microstructures (base metal, heat-affected-zone and welding bead) in welding. Moreover, the effect of external tensile stress during aging on phase separation of ferrite was also investigated. It was found that atom probe tomography is very useful for the analysis of phase separation in ferrite and the radial distribution function (RDF) is an effective method to compare the extent of phase separation at the very early stages. RDF is even more sensitive than frequency diagrams. In addition, the results indicate that the mechanical properties are highly connected with the phase separation in ferrite and other phenomena, such as Ni-Mn-Si-Cu clusters, that can also deteriorate the mechanical properties.<br><p>QC 20130308</p>
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O'Bree, Terry Adam, and s9907681@student rmit edu au. "Investigations of light scattering by Australian natural waters for remote sensing applications." RMIT University. Applied Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080110.140055.
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Remote sensing is the collection of information about an object from a distance without physically being in contact with it. The type of remote sensing of interest here is in the form of digital images of water bodies acquired by satellite. The advantage over traditional sampling techniques is that data can be gathered quickly over large ranges, and be available for immediate analysis. Remote sensing is a powerful technique for the monitoring of water bodies. To interpret the remotely sensed data, however, knowledge of the optical properties of the water constituents is needed. One of the most important of these is the volume scattering function, which describes the angular distribution of light scattered by a sample. This thesis presents the first measurements of volume scattering functions for Australian waters. Measurements were made on around 40 different samples taken from several locations in the Gippsland lakes and the Great Barrier Reef. The measurements were made by modifying an existing static light scattering spectrometer in order to accurately measure the volume scattering functions. The development of the apparatus, its calibration and automation, and the application of a complex series of post-acquisition data corrections, are all discussed. In order to extrapolate the data over the full angular range, the data was analysed using theoretical curves calculated for multi-modal size distributions using Mie light scattering theory applied to each data set. From the Mie fits the scattering and backscattering coefficients were calculated. These were compared with scattering coefficients measured using in situ sensors ac-9 and Hydroscat-6, and with values from the literature. The effect of chlorophyll a concentrations on the scattering coefficients was examined, and a brief investigation of the polarisation properties of the samples was also undertaken. Finally the angular effects on the relationship between the backscattering coefficient and the volume scattering function were investigated. This is important as in situ backscattering sensors often assume that measuring at a single fixed-angle is a good approximation for calculating the backscattering coefficient. This assumption is tested, and the optimal measurement angle determined.
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Kowalski, Michael Władisław. "Comparative study of oscillatory integral, and sub-level set, operator norm estimates." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4687.
Full textAbstract:
Oscillatory integral operators have been of interest to both mathematicians and physicists ever since the emergence of the work Theorie Analytique de la Chaleur of Joseph Fourier in 1822, in which his chief concern was to give a mathematical account of the diffusion of heat. For example, oscillatory integrals naturally arise when one studies the behaviour at infinity of the Fourier transform of a Borel measure that is supported on a certain hypersurface. One reduces the study of such a problem to that of having to obtain estimates on oscillatory integrals. However, sub-level set operators have only come to the fore at the end of the 20th Century, where it has been discovered that the decay rates of the oscillatory integral I(lambda) above may be obtainable once the measure of the associated sub-level sets are known. This discovery has been fully developed in a paper of A. Carbery, M. Christ and J.Wright. A principal goal of this thesis is to explore certain uniformity issues arising in the study of sub-level set estimates.
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Pulpitel, Tamara. "Ecological Immunology: Immune Defence Strategies of Australian Locusts." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12834.
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This thesis looks at the immunology of Australian locusts in a broad ecological context. By investigating some of the ecological parameters commonly known to influence locusts, this work ties many of the underlying immune-based mechanisms of locusts, ultimately providing insight into the success of these animals in the field. In the context of locust biocontrol strategies, this is particularly important. In Chapter 2, the density-dependent prophylaxis hypothesis was tested in Chortoicetes terminifera; a theory predicting that group-living animals invest more in immune function compared to solitarious conspecifics. Through the use of several conventional immune assays, C. terminifera was found to both support and oppose the theory, accounting for the contradictory literature currently existing on this topic. The effect of cannibalism on disease transmission was investigated in Chapter 3. Starved locusts were found to significantly cannibalise uninfected over fungal-infected victims. Without an alternative food source, locusts succumbed to starvation rather than consume infected victims, revealing a striking adaptation of infection avoidance. Chapter 4 investigated predictive immune response in C. terminifera. After measuring several immune parameters in locusts exposed to live or dead infected conspecifics, physiological immune anticipation was not detected. In Chapter 5, gene expression assays were developed in Locusta migratoria to investigate immune gene expression variation across different tissues and immune states. These assays found distinct tissue-specificity across genes, highlighting the importance of tissue selection in such assays. Gene expression assays were applied in Chapter 6 to investigate variation in locust immunity in response to bacterial introduction to the gut. Results suggested that alteration of microbiota communities could induce subtle immune responses within hosts, supporting the need for further study in this field.
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Balkew, Teshome Mogessie. "The SIR Model When S(t) is a Multi-Exponential Function." Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etd/1747.
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The SIR can be expressed either as a system of nonlinear ordinary differential equations or as a nonlinear Volterra integral equation. In general, neither of these can be solved in closed form. In this thesis, it is shown that if we assume S(t) is a finite multi-exponential, i.e. function of the form S(t) = a+ ∑nk=1 rke-σkt or a logistic function which is an infinite-multi-exponential, i.e. function of the form S(t) = c + a/b+ewt, then we can have closed form solution. Also we will formulate a method to determine R0 the basic reproductive rate of an infection.
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Engvall, Gunn. "Cancer during Adolescence : Coping Shortly after Diagnosis and Psychosocial Function during the Acute and Extended Phase of Survival." Doctoral thesis, Uppsala universitet, Pediatrik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-157094.
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In this thesis coping shortly after diagnosis and psychosocial function during the acute and extended phase of survival was investigated for individuals struck by cancer during adolescence. Sixty-one participants were recruited and data were collected from four to eight weeks (T1) up to four years (T7) after diagnosis. Study I: the aim was to describe how participants (n=56) cope with cancer-related distress in response to closed and open-ended questions. In response to closed-ended questions, the majority reported emotion-focused strategies, and in response to open-ended questions they reported meaning-based and problem-focused strategies. Study II: the aim was to investigate nurses’ and physicians’ ability to identify which coping strategies participants (n=48) use. Neither nurses nor physicians were successful in identifying which strategies participants used, although physicians were somewhat better. Study III: the aim was to identify participants’ (n=61) psychosocial states. Three states were identified: poor (A), average (B), and good (C). From 18 months after diagnosis more participants than expected by chance were in state C. At T7 77% were in State C and 15% in State A. Female gender, divorced parents, and using distracting to cope was related to State A and B. Study IV: the aim was to describe negative and positive cancer-related consequences reported (n=32) three and four years after diagnosis and to establish whether using certain strategies at T1 was related to reports of certain consequences at T7. The majority reported negative and positive consequences and a relation between using distracting to cope at T1 and reporting bodily concerns at T7 was established. In conclusion: it is difficult for nurses and physicians to identify how adolescents recently diagnosed with cancer cope with distress; the majority of individuals diagnosed with cancer during adolescence experience a state of good psychosocial function during the extended phase of survival, and distress and personal growth often go hand in hand after cancer during adolescence.
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Carpels, Simon. "Royal Power and Bureaucracy : The Function of the Högste Ombudsman in the Last Phase of theGreat Northern War." Thesis, Uppsala universitet, Historiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-176500.
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The power struggle between the Charles XII and his bureaucracy after the crushing defeat inPoltava (1709) mainly concerned the unwillingness of the latter to raise a new army that could beshipped to Pomerania. In reaction to this disobedience the king reformed his bureaucracy.Among other things, the Carolinian reforms introduced the högste ombudsman. The office was toenforce the law and supervise all civil servant and military officers. This thesis deals with thequestion of how the högste ombudsman functioned within this power struggle. The source materialconsists of the correspondence between the högste ombudsman and various bureaucratic institutionsfrom every level of society.By consistently prosecuting civil servants and military officers and enforcing the law, he wasable to guarantee the functioning of the bureaucracy and at the same time fulfilled an importantideological function. He showed Swedish society that the bureaucracy was controlled and thatdisobedience was not tolerated regardless of social standing. This is especially apparent in hisactivities with the central and regional authorities. The latter were strictly controlled as they wereinstrumental in the supervision of the local authorities. However, as a side effect of theCarolinian reforms, the högste ombudsman had to answer many requests from local authorities thatnot always directly related to the main objectives of his office. Moreover, this indicates that thepriority of the högste ombudsman lied with the supervision of the central and regional authorities.By setting examples to the bureaucracy and society that criminal activities and disobediencewas not tolerated, he fulfilled his duty as royal instrument of coercion. He helped to the kingpursue the Swedish war effort against the will of the bureaucracy. This thesis provides anenhanced understanding of the royal policy of Charles XII and delivers a valuable account ofhow an autocratic monarch attempted to regain control over his bureaucracy.
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Chan, Christopher K. W. "Potential prebiotic roles of (amino-)acylation in the synthesis and function of RNA." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/245078.
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The Sutherland group recently demonstrated that from a mixture of oligoribonucleotide-2'- or 3'-phosphates the latter is chemoselectively acetylated. This is shown to mediate a template-directed ligation to give predominantly 3',5'-linked RNA that is acetylated at the ligation junction (acetyl-RNA). It was suggested that RNA emerged prebiotically via acetyl-RNA and also is proposed to have favourable genotypic properties due to greater propensity to form duplex structure. To study the properties of acetyl-RNA, their synthesis by solid-phase chemistry was required and described is the design of a 2'/3'-O-acetyl orthogonal protecting group strategy. Key to the orthogonal protecting group strategy is the use of (2-cyanoethoxy)carbonyl for the protection of the nucleobase exocyclic amines and a photolabile solid-phase linker group that allowed partial on-column deprotection. The synthesis of the 2'/3'-O-acetyl and 2'/3'-O-TBDMS phosphoramidites, in addition to preparation of a photolabile solid-phase support, are described. With the materials to hand the procedures for an automated synthesis of acetyl-RNA were optimised and several acetyl-RNA oligonucleotides were synthesised. The duplex stability of acetyl-RNA with up to four sites of 2'-O-acetylation were assessed by UV melting curve analysis. Remarkably, the acetyl groups caused a consistent decrease in Tm of between 3.0-3.2 °C. Thermodynamic parameters indicated a decrease in duplex stability that was consistent with a decrease in hydration of the minor groove resulting in a reduction of the stabilising hydrogen bonding network. The stability of a tetraloop was also found to decrease on acetylation. The acetylated- tetraloop it is able to form duplex at lower concentrations than the natural tetraloop. Additionally, it is more stable at high concentrations, indicating that acetyl-RNA favours duplex over other secondary structure. These properties are considered to give acetyl-RNA competitive advantage for their non-enzymatic replication. Aminoacylation of RNA is an important process in modern biology but the intermediacy of aminoacyl-adenylates is considered to be prebiotically implausible. A potentially prebiotic aminoacylation of nucleoside-3'-phosphates, selective for the 2'-hydroxyl, is presented. However, it was thought the aminoacylation yields could be improved and so a search for an alternative activator was conducted. Oligoribonucleotide-3'-phosphates were exposed to the aminoacylation conditions and selective aminoacylation at only the 2'-hydroxyl of the 3'-end was observed. In particular, the aminoacylation of a trimer lends support to Sutherland’s theory of a linked origin of RNA and coded peptide synthesis.
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Zhou, Jing. "An Atom-Probe Tomography Study of Phase Separation in Fe-Cr Based Steels." Doctoral thesis, KTH, Metallografi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150796.
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Stainless steels are very important engineering materials in a variety of applications such as in the food industry and nuclear power plants due to their combination of good mechanical properties and high corrosion resistance. However, ferrite-containing stainless steels are sensitive to the so-called ‘475°C embrittlement’, which is induced by phase separation of the ferrite phase, where it decomposes into Fe-rich ferrite (α) and Cr-rich ferrite (α'). The phase separation is accompanied with a severe loss of toughness. Therefore, the upper service temperature of ferrite-containing stainless steels in industrial applications has been limited to around 250°. In the present work, Fe-Cr based steels were mainly investigated by atom probe tomography. A new method based on the radial distribution function (RDF) was proposed to quantitatively evaluate both the wavelength and amplitude of phase separation in Fe-Cr alloys from the atom probe tomography data. Moreover, a simplified equation was derived to calculate the amplitude of phase separation. The wavelength and amplitude was compared with evaluations using the auto-correlation function (ACF) and Langer-Bar-on-Miller (LBM) method, respectively. The results show that the commonly used LBM method underestimates the amplitude of phase separation and the wavelengths obtained by RDF shows a good exponential relation with aging time which is expected from the theory. The RDF is also an effective method in detecting the phenomena of clustering and elemental partitioning. Furthermore, atom probe tomography and the developed quantitative analysis method have been applied to investigate the influence of different factors on the phase separation in Fe-Cr based alloys by the help of mainly mechanical property tests and atom probe tomography analysis. The study shows that: (1) the external tensile stress during aging enhances the phase separation in ferrite. (2) Phase separation in weld bead metals decomposes more rapidly than both the heat-affected-zone metals and the base metals mainly due to the high density of dislocations in the welding bead metals which could facilitate the diffusion. (3) The results show that Ni and Mn can enhance the phase separation comparing to the binary Fe-Cr alloy whereas Cu forms clusters during aging. (4) Initial clustering of Cr atoms was found after homogenization. Two factors, namely, clustering of Cr above the miscibility gap and clustering during quenching was suggested as the two responsible mechanisms. (5) The homogenization temperatures significantly influence the evolution of phase separation in Fe-46.5at.%Cr.<br><p>QC 20140910</p><br>Spinodal Project
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Nowotny, Thomas. "Phase transitions and multifractal properties of random field Ising models." Doctoral thesis, Universitätsbibliothek Leipzig, 2004. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-37023.
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In dieser Arbeit werden Zufallsfeld-Ising-Modelle mit einem eingefrorenen dichotomen symmetrischen Zufallsfeld für den eindimensionalen Fall und das Bethe-Gitter untersucht. Dabei wird die kanonische Zustandssumme zu der eines einzelnen Spins in einem effektiven Feld umformuliert. Im ersten Teil der Arbeit werden das mulktifraktale Spektrum dieses effektiven Feldes untersucht, Übergänge im Spektrum erklärt und Ungleichungen zwischen lokalen und globalen Dimensionsbegriffen bewiesen, die eine weitgehend vollständige Charakterisierung des multifraktalen Spektrums durch eine Reihe von Schranken erlauben. Ein weiterer Teil der Arbeit beschäftigt sich mit einer ähnlichen Charakterisierung des Maßes der lokalen Magnetisierung, das aus dem Maß des effektiven Feldes durch Faltung hervorgeht. In diesem Zusammenhang wird die Faltung von Multifraktalen in einem allgemeineren Rahmen behandelt und Zusammenhänge zwischen den multifraktalen Eigenschaften der Faltung und denen der gefalteten Maße bewiesen. Im dritten Teil der Dissertation wird der Phasenübergang von Ferro- zu Paramagnetismus im Modell auf dem Bethe Gitter untersucht. Neben verbesserten exakten Schranken für die Eindeutigkeit des paramagnetischen Zustands werden im wesentlichen drei Kriterien für die tatsächliche Lage des Übergangs angegeben und numerisch ausgewertet. Die multifraktalen Eigenschaften des effektiven Felds im Modell auf dem Bethe-Gitter schließlich erweisen sich als trivial, da die interessanten Dimensionen nicht existieren<br>In this work random field Ising models with quenched dichotomous symmetric random field are considered for the one-dimensional case and on the Bethe lattice. To this end the canonical partition function is reformulated to the partition function of one spin in an effective field. In the first part of the work the multifractal spectrum of this effective field is investigated, transitions in the spectrum are explained and inequalities between local and global generalized fractal dimensions are proven which allow to characterize the multifractal spectrum bei various bounds. A further part of the work is dedicated to the characterization of the measure of the local magnetization which is obtained by convolution of the measure of the effective field with itself. In this context the convolution of multifractals is investigated in a more general setup and relations between the multifractal properties of the convolution and the multifractal properties of the convoluted measures are proven. The phase transition from ferro- to paramagnetismus for the model on the Bethe lattice is investigated in the third part of the thesis. Apart from improved exact bounds for the uniqueness of the paramagnetic state essentially three criteria for the transition are developped and numerically evaluated to determine the transition line. The multifractal properties of the effective field for the model on the Bethe lattice finally turn out to be trivial because the interesting dimensions do not exist
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El, hog Sahbi. "Transition de phase dans les films magnétiques minces avec interactions concurrentes." Thesis, Cergy-Pontoise, 2017. http://www.theses.fr/2017CERG0843/document.
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Dans cette thèse nous étudions les transitions de phase et leurs propriétés thermodynamiques au sein de couches minces en se basant sur des simulations Monte-Carlo et sur le formalisme de la fonction de Green .Dans le premier chapitre, nous étudions le modèle de Blume-Emery-Griffith pour un film mince sur réseaux triangulaires empilés. Le spin $S_i$ dans ce modèle prend trois valeurs (+/-1,0). Notre travail a été motivé par le désir de vérifier si a nature de la transition de phase se conserve quand on réduit l'épaisseur du film. En utilisant la simulation Monte Carlo, nous montrons qu'il existe une valeur critique d'anisotropie D où la transition change de nature. Nous montrons ainsi que la nature premier ordre ne disparaît pas lorsque nous réduisons l'épaisseur du film contrairement à d'autres systèmes.Dans le deuxième chapitre, nous étudions les propriétés quantiques des couches mince hélimagnétiques. Nous montrons qu'il existe des modes de surface qui affectent la magnétisation de surface, nous montrons également que les fluctuations quantiques provoquent la contraction des spins à T=0 et donnent lieu à un croisement entre les magnétisations des couches à basse température. Nous nous intéressons ensuite à l'effet d'un champ magnétique appliqué perpendiculairement à la surface du film. Nous montrons que les spins réagissent en créant une configuration particulière. En utilisant la simulation Monte Carlo nous étudions la transition de phase en fonction de l'intensité du champ appliqué. Nous montrons que le système subit une transition de phase déclenchée par la destruction des composantes transversales xy des spins de certaines couches. À basse température, nous étudions les effets des fluctuations quantiques en utilisant la méthode des fonctions de Green. Les résultats montrent que la contraction des spins à T=0 est différente d'une couche à l'autre, et que la croisement des magnétisations de couche dépend de l'ampleur des angles hélicoïdaux.Dans le troisième chapitre, nous introduisons l'interaction de Dzyaloshinskii-Moriya. Il a été montré dans divers travaux que l'interaction DM est à l'origine de formation des skyrmions et de nouveau genre de domaines Walls. Nous nous intéressons aux propriétés quantiques d'un système de spins qui interagissent les uns avec les autres via une interaction DM et une interaction ferromagnétique. En utilisant la méthode "steepest descend", nous avons trouvé un état fondamental non-colinéaire qui est dû à la compétition entre l'interaction ferromagnétique et l'interaction asymétrique DM. Utilisant la théorie des fonctions de Green pour calculer le spectre des ondes de spin et la magnétisation des couches à température finie en deux et trois dimensions ainsi que dans un film mince avec des effets de surface. Nous avons constaté que l'excitation des ondes de spin dans les cristaux 2D et 3D est stable à T=0 sans nécessiter d'anisotropie, mais dans le cas d'un film mince nous avons besoin d'une faible anisotropie pour stabiliser le spectre en raison du manque de voisins à la surface. On trouve aussi que l'énergie des ondes de spin est proportionnelle à $K^2$ pour les faibles valeurs de DM et une proportionnalité en $K$ pour les interactions fortes.Dans le quatrième chapitre, nous nous intéressons aux cristaux de skyrmion crées grâce à la compétition entre l'interaction ferromagnétique, le DM et le champ magnétique appliqué. Ces skyrmions s'organisent dans une structure périodique, ils ont été observés expérimentalement dans les composés MnSi, FeCoSi et dans les semiconducteurs dopés. En utilisant la simulation Monte Carlo, nous montrons que les cristaux de skyrmions sont stable à des températures finies et jusqu'à la transition où la structure topologique de chaque skyrmion et la structure périodique sont détruites. Nous étudions également la relaxation des skyrmions dans la phase cristalline et nous constatons que le temps de relaxation suit une loi exponentielle étirée<br>In this thesis, we study the phase transition and thermodynamic properties of classical and quantum spin models in thin films using both Green's function and standard Monte Carlo simulation.In chapter 1, we study the Blume-Emery-Griffith model. This model has been introduced to describe the mixing phase of superfluid He$^4$ ($S_i=pm$ 1) and normal fluid He$^3$ ($S_i$= 0) at low temperatures, such system undergoes two kinds of phase transition, first and second-order ones. Using Monte Carlo simulation, we show that there exists a critical value of anisotopy D$below (above) which the transition is of second (first) order, and that the first order nature of transition does not disappear when we reduce the film thickness unlike in other systems where the bulk first-order transition becomes second order with small thickness. In the Helium vocabulary, we show that the film surfaces have a deficit of He$^4$ with respect to interior layers of the film.In chapter 2 we first study quantum properties of a helimagnetic thin film. We show that there exist surface acoustic and optical modes which affect the surface magnetization. We also show that quantum fluctuations cause the spin contraction at $T$=0 and give rise to a cross-over between layer magnetizations at low temperatures. In the second part of chapter 2, we are interested in the effect of an external magnetic field applied. We show that spins react to a moderate applied magnetic field by creating a particular spin configuration along the $c$-axis. Using Monte Carlo simulation we study the phase transition as functions of the magnetic field strength. We show that the system undergoes a phase transition triggered by the destruction of the transverse xy spin-components. At low temperatures, we investigate effects of quantum fluctuations using Green's function method. The results show that the zero-point spin contraction is different from layer to layer. We also find a crossover of layer magnetizations which depends on the magnitude of helical angles.In the third chapter, we introduce the in-plane Dzyaloshinskii-Moriya interaction (DM). It has been showed in various works that the DM interaction is at the origin of topological skyrmions and a new kind of magnetic domain walls. In this chapter, we are interested in the spin-wave properties of a system of spins interacting with each other via a DM interaction. Using the steepest descend method we found a non-collinear ground state which is due to the competition between the ferromagnetic and the asymmetric DM interaction. We use the Green's function theory to calculate the spin-wave spectrum and the layer magnetization at finite temperatures in two and three dimensions as well as in a thin film with surface effects. We found that the spin-wave excitation in 2D and 3D crystals is stable at $T$=0 without the need of an anisotropy, but in the case of a thin film we need a small anisotropy to stabilize the spin-wave spectrum because of the lack of neighbors at the surface. We find also that the spin-wave energy is proportional to $k^2$ for a small DM interaction and is linear in $k$ for a strong one.Finally, in the fourth chapter we are interested in skyrmion crystals created by the competition between the ferromagnetic interaction and the DM interaction under an applied magnetic field. They arrange themselves in a periodic structure. These skyrmion crystals have been experimentally observed in MnSi compounds and in doped semiconductors. Using Monte Carlo simulation, we show that skyrmion crystals are stable at finite temperatures up to a transition temperature where the topological structure of each skyrmion and the periodic structure of skyrmions are destroyed. We also investigate the relaxation of the skyrmions in the crystalline phase and find that the relaxation time follows a stretched exponential law which is a characteristic of slowly-relaxed systems such as spin glasses
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Engler, William O. III. "A methodology for creating expert-based quantitative models for early phase design." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47670.
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Early systems engineering and requirements definition requires quantitative information about potential solutions prior to having sufficient information or time to develop detailed models. This research develops and demonstrates a transparent and repeatable process for rapidly creating quantitative models that leverage existing expert knowledge. This process is built upon established modeling frameworks and current literature for low fidelity modeling and hierarchical expert-based methods.
The process includes system definition using interactive morphological analysis and gathering information from subject-matter experts with computer-based interfaces in order to create a series of linear performance models. Available volunteers provided data for a relevant aerospace design to test the process as a whole and several hypotheses about specific methodological decisions made during the development. The collected data was analyzed for similarity among participants and for similarity to model parameters of an existing trusted truth model. The results of the analysis demonstrated the ability for expert-based models to accurately match the behavior of the truth models and of historical data.
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Hirschhorn, Andrew David. "Coronary Artery Bypass Graft Surgery: Exercise Testing and Prescription in the Acute Perioperative Phase." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/367852.
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The general aim of the research presented in this thesis was to investigate the
impact of Phase I (in-hospital) physiotherapy intervention on the restoration of
functional capacity after coronary artery bypass graft surgery (CABG).<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Physiotherapy and Exercise Science<br>Griffith Health<br>Full Text
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Pardo, Gonzalez Mauricio. "MEMS-based phase-locked-loop clock conditioner." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43643.
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Ultra narrow-band filters and the use of two loops in a cascade configuration dominate current clock conditioners based on phase-locked-loop (PLL) schemes. Since a PLL exhibits a low-pass transfer function with respect to the reference clock, the noise performance at very close-to-carrier offset frequencies is still determined by the input signal. Although better cleaning can be achieved with extremely narrow loops, an ultra low cut-off frequency could not be selected since the stability of the configuration deteriorates as the filter bandwidth is reduced. This fact suggests that a full-spectrum clock conditioning is not possible using traditional PLL architectures, and an alternative scheme is necessary to attenuate the very-close-to-carrier phase noise (PN). In addition, ultra-narrow loop filters can compromise on-chip integration because of the large size capacitors needed when chosen as passive. Input signal attenuation with relaxed bandwidth requirements becomes the main aspect that a comprehensive clock cleaner must address to effectively regenerate a reference signal.
This dissertation describes the Band-Reject Nested-PLL (BRN-PLL) scheme, a modified PLL-based architecture that provides an effective signal cleaning procedure by introducing a notch in the input transfer function through inner and outer loops and a high-pass filter (HPF). This modified response attenuates the reference-signal PN and reduces the size of the loop-filter capacitors substantially. Ultra narrow loops are no longer required because the notch size is related to the system bandwidth. The associated transfer function for the constitutive blocks (phase detectors and local oscillators) show that the output close-to-carrier and far-from-carrier PN sections are mainly dominated by the noise from the inner-PLL phase detector (PD) and local oscillator (LO) located in the outer loop, respectively. The inner-PLL PD transfer function maintains a low-pass characteristic with a passband gain inversely proportional to the PD gain becoming the main contribution around the carrier signal. On the other hand, the PN around the transition frequency is determined mainly by the reference and the inner-PLL LO. Their noise contributions to the output will depend on the associated passband local maxima, which is located at the BRN-PLL transition frequency. Hence, in this region, the inner-PLL LO is selected so that its effect can be held below that of the outer-PLL PD.
The BRN-PLL can use a high-Q MEMS-based VCO to further improve the transition region of the output PN profile and an LC-VCO as outer-PLL LO to reduce the noise floor of the output signal. In particular, two tuning mechanisms are explored for the MEMS-VCO: series tuning using varactors and phase shifting of a resonator operating in nonlinear regime. Both schemes are implemented to generate a tunable oscillator with no PN-performance degradation.
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Hehn, Anna-Sophia [Verfasser], and W. [Akademischer Betreuer] Klopper. "Explicitly correlated random-phase approximation: Development and application of a wave-function method / Anna-Sophia Hehn ; Betreuer: W. Klopper." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1170230539/34.
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Gebretsadik, Adane Samuel Gebretsadik. "INTERPLAY BETWEEN CHEMICAL AND MAGNETIC DISORDER IN SELECTED ALLOYS CLOSE TO A FERROMAGNETIC QUANTUM PHASE TRANSITION." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1527609152939816.
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