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The objective of this thesis is to investigate the impact of riverbank vegetation densities, which can vary greatly in natural river systems, on the flow hydrodynamics across the whole channel. A series of flume experiments are conducted with various riverbank vegetation densities and configurations. Flow velocities across the whole channel are recorded by either acoustic Doppler velocimetry (ADV) or acoustic Doppler velocimetry profiler (ADVP). Firstly, the performances of ADV and ADVP are assessed, before the impact of probe configurations on experimental results is evaluated for ADVP. The accuracy of the probe is discussed, and the best probe configurations for the given flow are suggested. The flow velocity progressively reduces at the vegetated riverbank and slightly increases at the main channel with increasing riverbank vegetation density. Turbulence intensity at the middle of the main channel and the riverbank toe increases with increasing vegetation density. However, at the riverbank region, turbulence intensity decreases due to the dramatic reduction of flow velocity. Geomorphic process feedback is given in the form of a case study, and practical recommendations for river restoration are provided. Bulk velocity, which is relevant to flow conveyance, is evaluated at each portion (main channel and riverbank) of the channel. In general, bulk velocity slightly increases at the main channel but dramatically decreases at the riverbank with increasing vegetation densities. The result of Nikuradse’s equivalent roughness also shows an increasing trend with increasing vegetation density. Bed shear stress is estimated using several methods, including the log Law of the Wall, turbulent kinetic energy and Reynolds stresses. The results obtained using all three methods show that bed shear stress considerably increases at the main channel and sharply decreases at the riverbank region for the shear stress with dense riverbank vegetation compared to the no vegetation case. Impulse is introduced as a new criterion to assess sediment transport both at the free stream portion and at the vegetated region in turbulent flow. With a range of reasonably assumed critical velocities and critical impulses, the frequency of impulse closely follows the same trend observed for shear stresses across the channel width.

The main aim of this thesis is to investigate multilingual mobile learning applications by using the wireless response system (WRS) as a case study. This application is developed and internationalised into fourteen languages, to allow students and teachers from different languages to use this application, with a view towards enhancing the educational environment. Additionally, one related aim is to detect the usability of the multilingual mobile learning application in these languages, by measuring the effectiveness, efficiency, user satisfaction and comprehensibility of the WRS, through the adoption of the Fuzzy theory. Drawing on a survey of 295 participants, the results indicate significant differences between the original language of the interface (i.e., English) and certain other language interfaces, in terms of its effectiveness, efficiency, user satisfaction and comprehensibility. These variances make the usability level of the WRS in the English language interface significantly better and statistically different from the Netherlands, Dutch, French, Italian, Swedish, Russian, Romanian, Spanish and Turkish languages. However, the results show that the usability level of the WRS interface in the English language is not significantly better and statistically different from the Arabic, Chinese, Portuguese, Malay and Polish languages. These results encourage future studies to further improve the mobile learning application in languages that demonstrated low usability values. These results will help researchers in this field to recognise the problems and weaknesses of multilingual mobile learning applications, towards improving and solving them. The significance of this thesis lies in making the WRS application available in fourteen languages, and also in measuring the usability of these fourteen languages through the application of (1) Fuzzy theory and (2) SPSS software. The use of the Fuzzy theory to measure the collected data leads to obtaining accurate and precise results, facing the vagueness and ambiguities of the user‟s language surrounding the analysis process. In other words, this theory adds a clearer and more accurate understanding of the vagueness of language‟s uncertainty, opinion and ambiguous expressions that are hidden in different users‟ backgrounds.

Today, one of the biggest challenges that E-management systems face is the explosive growth of operating data and to use this data to enhance services. Web usage mining has emerged as an important technique to provide useful management information from user's Web data. One of the areas where such information is needed is the Web-based academic digital libraries. A digital library (D-library) is an information resource system to store resources in digital format and provide access to users through the network. Academic libraries offer a huge amount of information resources, these information resources overwhelm students and makes it difficult for them to access to relevant information. Proposed solutions to alleviate this issue emphasize the need to build Web recommender systems that make it possible to offer each student with a list of resources that they would be interested in. Collaborative filtering is the most successful technique used to offer recommendations to users. Collaborative filtering provides recommendations according to the user relevance feedback that tells the system their preferences. Most recent work on D-library recommender systems uses explicit feedback. Explicit feedback requires students to rate resources which make the recommendation process not realistic because few students are willing to provide their interests explicitly. Thus, collaborative filtering suffers from “data sparsity” problem. In response to this problem, the study proposed a Web usage mining framework to alleviate the sparsity problem. The framework incorporates clustering mining technique and usage data in the recommendation process. Students perform different actions on D-library, in this study five different actions are identified, including printing, downloading, bookmarking, reading, and viewing the abstract. These actions provide the system with large quantities of implicit feedback data. The proposed framework also utilizes clustering data mining approach to reduce the sparsity problem. Furthermore, generating recommendations based on clusters produce better results because students belonging to the same cluster usually have similar interests. The proposed framework is divided into two main components: off-line and online components. The off-line component is comprised of two stages: data pre-processing and the derivation of student clusters. The online component is comprised of two stages: building student's profile and generating recommendations. The second stage consists of three steps, in the first step the target student profile is classified to the closest cluster profile using the cosine similarity measure. In the second phase, the Pearson correlation coefficient method is used to select the most similar students to the target student from the chosen cluster to serve as a source of prediction. Finally, a top-list of resources is presented. Using the Book-Crossing dataset the effectiveness of the proposed framework was evaluated based on sparsity level, and Mean Absolute Error (MAE) regarding accuracy. The proposed framework reduced the sparsity level between (0.07% and 26.71%) in the sub-matrices, whereas the sparsity level is between 99.79% and 78.81% using the proposed framework, and 99.86% (for the original matrix) before applying the proposed framework. The experimental results indicated that by using the proposed framework the performance is as much as 13.12% better than clustering-only explicit feedback data, and 21.14% better than the standard K Nearest Neighbours method. The overall results show that the proposed framework can alleviate the Sparsity problem resulting in improving the accuracy of the recommendations.

Device to device (D2D) links density is expected to increase dramatically in future networks. The D2D user equipments (DUEs) reuse frequency resources to cover the next generation D2D-enabled cellular network requirements. The cellular user equipments (CUEs) and DUEs experience in-band emission interference (IEI) from DUEs that use adjacent frequencies. In this thesis, the IEI impact in D2D-enabled cellular network is investigated comprehensively. In the first part, the IEI from the DUEs to cellular links is initially mitigated for all time slots. An open loop power control (OLPC)-based scheme is introduced for the D2D discovery scenario to mitigate the IEI and compared with recent proposed methods. The scheme defines time slots to boost the DUEs transmission power, where the IEI is mitigated and the D2D link performance is improved. A simulation system is used to evaluate the IEI impact. The IEI from DUEs to cellular links is mitigated without taking into account the proposed power control can affect the DUEs that use the same frequency resource and the constraints can affect the D2D link performance. Therefore, the second part expands the IEI investigation, where the D2D-enabled cellular network is modelled by taking into account the IEI interferers using the stochastic geometry tool. The IEI impact is analysed and mitigated for all time slots by taking into account the D2D links performance. The IEI impact is evaluated theoretically in terms of coverage probability and data rate for cellular link side, successful probability and data rate for D2D link side. The IEI intra-cell and IEI inter-cell are investigated separately to detect the dominant part of IEI. The expected reuse factor of the D2D resource blocks (DRBs) is derived to examing the number of DUEs that can be served when the IEI is or is not taken into account. Following, a power-density based (PDB) strategy is proposed to mitigate the IEI by controlling the number of DUEs that use each DRB, and by allocating predefined DRBs to the DUEs that cause lowest interference power at the serving BS. The thinning process and Poisson hole process (PHP) are employed to remodel the network. The performance improvement can be achieved by employing this strategy is evaluated. The optimal DRBs setting is found that mitigates the IEI and improves the cellular link performance. Furthermore, the optimal power allocation (OPA) algorithm is proposed to mitigate the IEI by calculating the optimal DUEs transmission power profile that maximizes the DUEs sum rate and maintains the interference level at the BS below a predefined threshold. The performance improvement that can be achieved by employing this algorithm is also evaluated. It is concluded that, in a D2D-enabled cellular network, the IEI impact is significant and needs to be considered to evaluate the performance of the future network accurately. Thus, the proposed model can be used to represent and evaluate the future network. Also, by employing the PDB strategy, the IEI can be mitigated effectively if the D2D links performance has higher priority than the number of DUEs required to be served for D2D discovery and transmission data scenarios. In case the required number of served DUEs in one time slot cannot be covered by PDB, the OPA algorithm and the OLPC-based strategy can be used for D2D data transmission and D2D discovery scenarios, respectively.

Orientador: Ricardo Luiz Viana / Disertação (mestrado) - Universidade Federal do Paraná / Resumo: Este trabalho visa mediante a Formulação Hamiltoniana para linhas de campo, estudar a formação das ilhas magnéticas na região periférica de uma coluna de plasma sujeita à ação de um limitador magnético ergódico. Para este fim nós utilizamos um modelo semelhante ao de Martin e Taylor, o que tomou o problema tratável analiticamente. Mediante este modelo, e simulando a ação do limitador por meio de uma perturbação impulsiva, nós obtivemos tuna Hamiltoniana não-integrável. Reduzimos esta Hamiltoniana à forma da Hamiltoniana Paradigma, o que nos possibilitou aplicar o critério de Escande para obter a corrente crítica que gera a estocasticidade em larga escala. Uma comparação com o critério de Chirikov foi feita. Obtvemos também a semi-largura da ilha em função da corrente no limitador. / Abstract:This work aims to study magnetic island formation in the peripheral region of a plasma column under the action of an ergodic magnetic limiter, by means of the hamitonian formulation for magnetic field lines. We have used a model similar to the Martin-Taylor one, in order to treat this problem analitically. In this model, we have simulated the limiter action through an inpulsive perturbation, so that we obtain a nonintegrable hamiltonian. We have reduced this hamiltonian to the paradigm form, which have enabled us to apply Escande’s criterion to obtain the critical current for large-scale stochasticity. A comparison with Chirikov’s criterion has been made. We have also obtained the island half-width as a function of the limiter current.

Orientador : Ricardo Luiz Viana / Dissertaçao (mestrado) - Universidade Federal do Paraná / Resumo: Este trabalho tem como objetivo o estudo das características de certos sistemas não lineares acoplados na rede e sua sincronização. O sistema estudado consiste num oscilador não-linear sujeito a uma força periódica impulsiva, que no nosso caso pode ser aproximada por uma seqüência de funções delta. A utilização da técnica de mapeamento estroboscópico e a consideração do limite de rápida relaxação permite-nos obter um mapa unidimensional. Tomamos uma rede de tais mapas e estudamos sua dinâmica espaço-temporal, bem como a sincronização de mapas, através de acoplamentos local e global, que apresentam regimes dinâmicos regulares e caóticos. Propomos algumas novas formas de acoplamento: o acoplamento global do tipo exponencial e do tipo gaussiano. Nestes últimos acoplamentos a dinâmica do sítio na rede é determinada pela dinâmica de todos os sítios, de tal forma que o valor da intensidade do acoplamento decai numa forma exponencial ou numa forma gaussiana, respectivamente, de acordo com a separação entre os sítios. / Abstract: This work aims to study the characteristics of certain nonlinear systems coupled in a lattice and their synchronization. The system to be studied, which present limit cycles, consists of a nonlinear oscillator subjected a periodic impulsive force, that in our case can to be aproximated by a sequence of delta functions. The use of the technique of stroboscopic mapping and the consideration of the fast-relaxation limit allows us to obtain a one-dimensional map. We take a lattice of such maps and study its spatio-temporal dynamics, and the synchronization of maps too, locally and globally, presenting regular and chaotic dynamical regimes. We propose some new kinds of couplings, such as the global coupling of the exponential kind and of the gaussian kind. In these latter couplings the dynamics of the site in the lattice is determined all other sites, in such a way that coupling intensity decays in an exponential or gaussian way, depending on the separation between the sites.

Orientador: Vicente Roberto Dumke / Dissertaçao (mestrado) - Universidade Federal do Paraná / Resumo: O presente trabalho teve por objetivo a análise do comportamento plástico de amostras de LiF submetidas à implantação iônica e radiações (Raios-X e Raios-Gama). O estudo foi realizado através da associação entre as técnicas de dureza Vickers modificada (Hv*, fotoelasticidade e ataque químico. Esta combinação revelou-se muito útil em função da maior quantidade de informações obtidas, principalmente, quando o uso de uma única técnica é de certo modo limitada nas medidas de variação da plasticidade de amostras cristalinas. Desta combinação, foi possível obter-se a relação gama= l/d onde l é a medida do alcance do padrão de distribuição das discordâncias e d é a diagonal de impressão, que é muito mais ampla nas informações sobre o comportamento plástico das amostras estudadas. A partir dos resultados obtidos, verifica-se que existe uma alteração bastante significativa na plasticidade das amostras implantadas e das irradiadas. Esta modificação no comportamento plástico produz na superfície das amostras de LiF implantadas, uma fragilização de caráter anisotrópico. Entretanto , nas irradiadas esta não foi verificada nas doses usadas. Nas amostras implantadas com N+2 é verificada a validade da relação l alfaP0,5 dentro dos limites de dose usadas(1x10^13 íons/cm2 a 1x10^17 íons/cm2 ). Podemos ainda relacionar nas mesmas a mobilidade das discordâncias com a dose recebida, através da relação ln D alfa l. Para as amostras irradiadas também foi possível verificar a validade da segunda relação. / Abstract: The present works objective is the analysis of plastic behaviour of LiF samples subject to ionic implantation, X and gama irradiation. Modified Vickers hardness (Hv*p), photoelasticity and chemical etching tecniques were employed to develop this study. This combination, itself, reveals to be useful due to the larger amount of information obtained, mainly because when only one technique is used, the measurement of variations in plastic behaviour of crystal samples is limited. From this combinations, it's possible to attaim the gama = l/d relation, that offers more extensive informations about the plasticity of the studies samples, where l. is the measure of the dislocation range and d is the measure of the piramidal edge. This work results a significant change in the implanted samples plasticity and this also happens in the irradiated samples. These modifications in the plastic behaviour render the samples fragile, although anisotropic, only for LiF. This does not happen in the irradiated samples in the used doses. In the samples implanted from 10^13 ions/cm2 to 10^17 ions/cm2 of N2+ the validity of the l alfa P^0,5 relation is verified and a new relation of ln D alfa l is established.

Orientador: Carlos M. Lepienski / Tese (doutorado) - Universidade Federal do Parana

Orientador: Carlos Maurício Lepienski / Tese (doutorado) - Universidade Federal do Paraná