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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Smoothing And Differentiation Of Dynamic Data

Titrek, Fatih 01 May 2010 (has links) (PDF)
Smoothing is an important part of the pre-processing step in Signal Processing. A signal, which is purified from noise as much as possible, is necessary to achieve our aim. There are many smoothing algorithms which give good result on a stationary data, but these smoothing algorithms don&rsquo / t give expected result in a non-stationary data. Studying Acceleration data is an effective method to see whether the smoothing is successful or not. The small part of the noise that takes place in the Displacement data will affect our Acceleration data, which are obtained by taking the second derivative of the Displacement data, severely. In this thesis, some linear and non-linear smoothing algorithms will be analyzed in a non-stationary dataset.
232

Robust Framework for System Architecture and Hand-offs in Wireless and Cellular Communication Systems

Varma, Vishal V. 14 January 2010 (has links)
Robustness of a system has been defined in various ways and a lot of work has been done to model the robustness of a system, but quantifying or measuring robustness has always been very difficult. In this research, we develop a framework for robust system architecture. We consider a system of a linear estimator (multiple tap filter) and then attempt to model the system performance and robustness in a graphical manner, which admits an analysis using the differential geometric concepts. We compare two different perturbation models, namely the gradient with biased perturbations (sub-optimal model) of a surface and the gradient with unbiased perturbations (optimal model), and observe the values to see which of them can alternately be used in the process of understanding or measuring robustness. In this process we have worked on different examples and conducted many simulations to find if there is any consistency in the two models. We propose the study of robustness measures for estimation/prediction in stationary and non-stationary environment using differential geometric tools in conjunction with probability density analysis. Our approach shows that the gradient can be viewed as a random variable and therefore used to generate probability densities, allowing one to draw conclusions regarding the robust- ness. As an example, one can apply the geometric methodology to the prediction of time varying deterministic data in imperfectly known non-stationary distribution. We also compare stationary to non-stationary distribution and prove that robustness is reduced by admitting residual non-stationarity. We then research and develop a robust iterative handoff algorithm, relating generally to methods, devices and systems for reselecting and then handing over a mobile communications device from a first cell to a second cell in a cellular wireless communications system (GPRS, W-CDMA or OFDMA). This algorithm results in significant decrease in amount of power and/or result is a decrease of break in communications during an established voice call or other connection, in the field, thereby outperforming prior art.
233

Maximally smooth transition: the Gluskabi raccordation

Yeung, Deryck 24 August 2011 (has links)
The objective of this dissertation is to provide a framework for constructing a transitional behavior, connecting any two trajectories from a set with a particular characteristic, in such a way that the transition is as inconspicuous as possible. By this we mean that the connection is such that the characteristic behavior persists during the transition. These special classes include stationary solutions, limit cycles etc. We call this framework the Gluskabi raccordation. This problem is motivated from physical applications where it is often desired to steer a system from one stationary solution or periodic orbit to another in a ̒smooth̕ way. Examples include motion control in robotics, chemical process control and quasi-stationary processes in thermodynamics, etc. Before discussing the Gluskabi raccordations of periodic behaviors, we first study several periodic phenomena. Specifically, we study the self- propulsion of a number of legless, toy creatures based on differential friction under periodic excitations. This friction model is based on viscous friction which is predominant in a wet environment. We investigate the effects of periodic and optimal periodic control on locomotion. Subsequently, we consider a control problem of a stochastic system, under the basic constraint that the feedback control signal and the observations from the system cannot use the communication channel simultaneously. Hence, two modes of operation result: an observation mode and a control mode. We seek an optimal periodic regime in a statistical steady state by switching between the observation and the control mode. For this, the duty cycle and the optimal gains for the controller and observer in either mode are determined. We then investigate the simplest special case of the Gluskabi raccordation, namely the quasi-stationary optimal control problem. This forces us to revisit the classical terminal controller. We analyze the performance index as the control horizon increases to infinity. This problem gives a good example where the limiting operation and integration do not commute. Such a misinterpretation can lead to an apparent paradox. We use symmetrical components (the parity operator) to shed light on the correct solution. The main part of thesis is the Gluskabi raccordation problem. We first use several simple examples to introduce the general framework. We then consider the signal Gluskabi raccordation or the Gluskabi raccordation without a dynamical system. Specifically, we present the quasi-periodic raccordation where we seek the maximally ̒smooth̕ transitions between two periodic signals. We provide two methods, the direct and indirect method, to construct these transitions. Detailed algorithms for generating the raccordations based on the direct method are also provided. Next, we extend the signal Gluskabi raccordation to the dynamic case by considering the dynamical system as a hard constraint. The behavioral modeling of dynamical system pioneered by Willems provides the right language for this generalization. All algorithms of the signal Gluskabi raccordation are extended accordingly to produce these ̒smooth̕ transition behaviors.
234

Stationary solutions of linear ODEs with a randomly perturbed system matrix and additive noise

Starkloff, Hans-Jörg, Wunderlich, Ralf 07 October 2005 (has links) (PDF)
The paper considers systems of linear first-order ODEs with a randomly perturbed system matrix and stationary additive noise. For the description of the long-term behavior of such systems it is necessary to study their stationary solutions. We deal with conditions for the existence of stationary solutions as well as with their representations and the computation of their moment functions. Assuming small perturbations of the system matrix we apply perturbation techniques to find series representations of the stationary solutions and give asymptotic expansions for their first- and second-order moment functions. We illustrate the findings with a numerical example of a scalar ODE, for which the moment functions of the stationary solution still can be computed explicitly. This allows the assessment of the goodness of the approximations found from the derived asymptotic expansions.
235

Algorithms for Visual Maritime Surveillance with Rapidly Moving Camera

Fefilatyev, Sergiy 01 January 2012 (has links)
Visual surveillance in the maritime domain has been explored for more than a decade. Although it has produced a number of working systems and resulted in a mature technology, surveillance has been restricted to the port facilities or areas close to the coastline assuming a fixed-camera scenario. This dissertation presents several contributions in the domain of maritime surveillance. First, a novel algorithm for open-sea visual maritime surveillance is introduced. We explore a challenging situation with a camera mounted on a buoy or other floating platform. The developed algorithm detects, localizes, and tracks ships in the field of view of the camera. Specifically, our method is uniquely designed to handle a rapidly moving camera. Its performance is robust in the presence of a random relatively-large camera motion. In the context of ship detection, a new horizon detection scheme for a complex maritime domain is also developed. Second, the performance of the ship detection algorithm is evaluated on a dataset of 55,000 images. Accuracy of detection of up to 88% of ships is achieved. Lastly, we consider the topic of detection of the vanishing line of the ocean surface plane as a way to estimate the horizon in difficult situations. This allows extension of the ship-detection algorithm to beyond open-sea scenarios.
236

The mutual interaction between the time-mean atmospheric circulation and continental-scale ice sheets

Liakka, Johan January 2011 (has links)
Geomorphological evidence of glaciations exist for the Last Glacial Maximum (about 20 kyr ago). At this time, both North America and Eurasia were covered by extensive ice sheets which are both absent today. However, the temporal and spatial evolution of the ice sheets from the previous interglacial up to the fully-glaciated conditions at LGM is still unresolved and remains a vexing question in climate dynamics. The evolution of ice sheets is essentially controlled by the prevailing climate conditions. On glacial time-scales, the climate is shaped the by the orbital variations of the Earth, but also by internal feedbacks within the climate system. In particular, the ice sheets themselves have the potential to change the climate within they evolve. This thesis focuses on the interactions between ice sheets and the time-mean atmospheric circulation (stationary waves). It is studied how the stationary waves, which are forced by the ice-sheet topography, influence ice-sheet evolution through changing the near-surface air temperature. In this thesis, it is shown that the degree of linearity of the atmospheric response controls to what extent the stationary waves can reorganise the structure of ice sheet. Provided that the response is linear, the stationary waves constitute a leading-order feedback, which serves to increase the volume and deform the shape of ice sheets. If the stationary-wave response to ice-sheet topography is nonlinear in character, the impact on the ice-sheet evolution tends to be weak. However, it is further shown that the amplitude of the nonlinear topographical response, and hence its effect on the ice-sheet evolution, can be significantly enhanced if thermal cooling over the ice sheets is taken into account. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.
237

Moterų, sergančių vėžiu, emocinės būsenos ypatybės gydantis stacionare / Women’s with cancer emotional condition features during stationary treatment

Pilypaitė, Lidija 23 June 2009 (has links)
Tyrimo tikslas: nustatyti moterų, sergančių vėžiu, emocinės būsenos (emocinės įtampos ir pablogėjusios nuotaikos) ypatybes, kitimus gydantis stacionare bei jų sąsajas su subjektyviu savo sveikatos vertinimu, ligos sunkumu, amžiumi ir išsilavinimu. Tyrimas atliktas Kauno medicinos universiteto klinikų filiale Kauno onkologijos ligoninėje Onkoginekologiniame skyriuje 2008 liepos – rugpjūčio mėnesiais ir 2009 vasario – kovo mėnesiais. Dalyvauti tyrime pakviesta 141 moteris, 94 iš jų sutiko dalyvauti, 47 atsisakė. Tyrime lyginamoji grupė (N=44) yra moterys be vėžio diagnozės, kurioms diagnozuoti kiti ginekologiniai susirgimai. Gydymo pradžioje ir pabaigoje apklausta 41 moteris, t.y. 43.6 proc. tiriamųjų. Pagrindinė tiriamųjų praradimo priežastis buvo neplanuoti išrašymai iš ligoninės. Pirmiausia su tiriamosiomis atliekamas Struktūrinis klinikinis interviu, po to pacientės prašoma užpildyti Klausimyną depresijos pokyčiams vertinti bei Sveikatos klausimyną. Tyrimo rezultatai parodė, kad sergančios vėžiu moterys stacionarinio gydymo laikotarpiu yra blogesnės nuotaikos negu vėžiu nesergančios. Moterys, kurioms diagnozuotas III ir IV stadijos vėžys, nepatiria aukštesnės emocinės įtampos ir nėra blogesnės nuotaikos lyginant su moterimis, kurioms nustatytas I ir II stadijos vėžys. Sergančių vėžiu moterų emocinė įtampa ir nuotaika gydantis stacionare nekinta. Sergančioms vėžiu pacientėms, kurioms pirmo pokalbio metu nustatytas geresnis psichologinis – socialinis prisitaikymas... [toliau žr. visą tekstą] / Study aim: ascertain features and variation of women’s with cancer emotional condition (emotional tense and subdued mood) during stationary treatment and dependence on subjective health assessment, illness severity, age and education. The research was accomplished in Kaunas Medicine University Clinics subsidiary in Kaunas oncology hospital Department of Oncogynaecology during 2008 July – August and 2009 February – March. To participate in the research was invited 141 women, 94 of them accepted the invitation, 47 refused. The comparable group (N = 44) consisted of women without diagnosis of cancer but with other gynecological disorders. At the beginning and end of treatment 41 women (43,6% of participants) was interviewed. The main cause of loss of participants was unplanned discharges. Firstly structural clinical interview was held with participants. After it patients were asked to fill Questionnaire to evaluate change of depression and Health questionnaire. The results showed that women with cancer during stationary treatment are in more subdued mood than women without cancer. Women who had diagnosis of advanced cancer stages (III and IV) were not in more subdued mood and higher emotional tense to compare to women who had diagnosis of primary cancer stages (I and II). Women’s with cancer emotional tense and mood does not change during stationary treatment. Women’s with cancer, whom during the first interview better social – psychological adaptability was assessed... [to full text]
238

Šiaulių Pramonės gatvės aplinkos būklės įvertinimas ir sprendimai / Siauliai Pramones Street industrial environmental assessment and solutions

Grigorjeva, Alina 02 August 2011 (has links)
Darbe analizuojami teisės aktai reglamentuojantys aplinkos oro apsaugą, Europos Sąjungos direktyvos. Pateikiamos Lietuvos ir Europos Sąjungos priemonės taršai mažinti. Išanalizavus gautus duomenis, išryškėjo Pramonės gatvėje trys pagrindiniai stacionarūs taršos šaltiniai, kurie turi įtakos šiai gatvei. Viena didžiausių įmonių, tai AB „Šiaulių energija“ Pietinė katilinė, kuri vykdydamą savo veiklą per metus išmeta 94 % suminio emisijų kiekio lyginant su kitais stacionariais taršos šaltiniais. Išmatavus triukšmo lygius Pramonės gatvėje paaiškėjo, kad didžiausias triukšmo lygis būna prie įmonės UAB „Kalvis“ ir prie prekybos centro „Bruklinas“. Transporto srautas šioje gatvėje yra intensyviausias ryte ir vakare (piko valandomis). Vidutiniškai per valandą pravažiuoja 1500 automobilių. Norint sumažinti triukšmo lygius reikėtų įrengti želdinius, kurie taip pat dar ir valo aplinkos orą. Norint sumažint emisijų kiekius į atmosferą, įmonėms siūlyčiau įdiegti naujas technologijas, kurios mažiau terštų, pradėti naudoti efektyvesnius valymo įrenginius. / In this paper analyzes the laws governing environmental protection, air pollution, the EU Directive relating to the subject of my question. Submitted to the Republic of Lithuania and European Union environmental pollution measures maint. Major stationary sources of pollution are 3 firms in the Pramones street. The one of biggest firm is the AB „Siauliu energija“ Pietine katiline. This undertaking their activity during the year, emit 94% of total emissions in comparison with other companies. Measurement of noise levels in industry in the street showed that the maximum noise level is at UAB „Kalvis“ and the shopping center in „Bruklinas“. Traffic on this street is the most intense in the morning and evening (peak hours). An average of 1,500 per hour passing cars. To reduce the noise levels should be equipped with green stands, which are also designed for cleaning the air. For quantities are reduced emissions into the atmosphere, I would suggest that companies introduce new technologies that pollute less, start to use more efficient air cleaning devices.
239

Representation operators of metric and Euclidian charges

Bouafia, Philippe 07 January 2014 (has links) (PDF)
We study multiple valued functions with values in a Hilbert space. We introduce a possibledefinition of Sobolev spaces and the rightful notion of p energy. We prove the existence of pminimizers. Then we consider two-valued real functions of two variables which are stationarywith respect to both domain and range transformations. We prove their local Lipschitzcontinuity and use it to establish strong convergence in W1,2 to their unique blow-up at anypoint. We claim that the branch set of any such function consists of finitely many real analyticcurves meeting at nod points with equal angles. We also provide an example showing thatstationarity with respect to domain transformations only does not imply continuity.In a second part, we prove that there does not exist a uniformly continuous retractionfrom the space of continuous vector fields onto the subspace of vector fields whose divergencevanishes in the distributional sense. We then generalise this result using the concept of mcharges on any subset X _ Rn satisfying a mild geometric condition, there is no uniformlycontinuous representation operator for mcharges in X.
240

On Bootstrap Evaluation of Tests for Unit Root and Cointegration

Wei, Jianxin January 2014 (has links)
This thesis is comprised of five papers that all relate to bootstrap methodology in analysis of non-stationary time series. The first paper starts with the fact that the Dickey-Fuller unit root test using asymptotic critical value has bad small sample performance. The small sample correction proposed by Johansen (2004) and bootstrap are two effective methods to improve the performance of the test. In this paper we compare these two methods as well as analyse the effect of bias-adjusting through a simulation study. We consider AR(1) and AR(2) models and both size and power properties are investigated. The second paper studies the asymptotic refinement of the bootstrap cointegration rank test. We expand the test statistic of a simplified VECM model and a Monte Carlo simulation was carried out to verify that the bootstrap test gives asymptotic refinement. The third paper focuses on the number of bootstrap replicates in bootstrap Dickey-Fuller unit root test. Through a simulation study, we find that a small number of bootstrap replicates are sufficient for a precise size, but, with too small number of replicates, we will lose power when the null hypothesis is not true. The fourth and last paper of the thesis concerns unit root test in panel setting focusing on the test proposed by Palm, Smeekes and Urbain (2011). In the fourth paper, we study the robustness of the PSU test with comparison with two representative tests from the second generation panel unit root tests. In the last paper, we generalise the PSU test to the model with deterministic terms. Two different methods are proposed to deal with the deterministic terms, and the asymptotic validity of the bootstrap procedure is theoretically checked. The small sample properties are studied by simulations and the paper is concluded by an empirical example. / <p>Ogiltigt ISBN: 978-91-554-9069-0</p>

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