Error Resilient Coding tools are the methods to avoid or reduce the amount of corruption in video by altering the encoding algorithm. One of them is Flexible Macroblock Ordering (FMO) which provides us with ordering macroblocks of the frames flexibly. Six of them have definite ordering pattern and the last one, called explicit type, can get any order. In this thesis two explicit type algorithms, one of which is new, are explained and the performance of different FMO types in wired and wireless communication are evaluated. The first algorithm separates the important blocks into separate packets, so it equalizes the importance of packets. The proposed method allocates the important macroblocks according to a checkerboard pattern and employs unequal error protection to protect them more. The simulations are performed for wired and wireless communication and Forward Error Correction is used in the second stage of the simulations. Lastly the results of the new algorithms are compared with the performance of the other FMO types. According to the simulations the Proposed algorithm performs better than others when the error rate is very high and FEC is employed.

Θέμα της παρούσας εργασίας είναι η υλοποίηση και εξομοίωση δίκαιων αλγόριθμων χρονοπρογραμματισμού σε Grids και η σύγκρισή τους με κλασικούς αλγόριθμους χρονοπρογραμματισμού. Η βασική ιδέα πίσω από την τεχνολογία Grid και τις υπηρεσίες που παρέχει είναι η ενοποίηση υπολογιστικών και αποθηκευτικών πόρων και η συνολική θεώρηση τους από τους χρήστες. Με τον τρόπο αυτό γίνεται δυνατή η ανάπτυξη πολύπλοκων και απαιτητικών εφαρμογών, τόσο στον χώρο της επιστημονικής έρευνας, όσο και στα πλαίσια της παραγωγής εμπορικών λύσεων. Ένα τέτοιο σύστημα απαιτεί διαμοιρασμό των υπολογιστικών και άλλων πόρων καθώς και μεγάλες ταχύτητες σύνδεσης μεταξύ τους. Οι αλγόριθμοι χρονοπρογραμματισμού αναλαμβάνουν τον αποδοτικό διαμοιρασμό των πόρων ώστε να επιτυγχάνεται καλύτερη ποιότητα υπηρεσίας. Η αποτελεσματικότητα ενός αλγόριθμου χρονοπρογραμματισμού εξαρτάται από την συνάρτηση που θέλουμε να βελτιστοποιήσουμε, που με τη σειρά της εξαρτάται από τεχνο-οικονομικά κριτήρια. Στην προσπάθεια βελτιστοποίησης της εκάστοτε συνάρτησης ευνοούνται κάποιες προς εκτέλεση διεργασίες έναντι άλλων. Ένας δίκαιος αλγόριθμος χρονοπρογραμματισμού όμως θα πρέπει να συμπεριφέρεται με τον ίδιο τρόπο σε όλες τις διεργασίες ανεξαρτήτως των χαρακτηριστικών τους. Στην εργασία που θα παρουσιάσουμε, αναλύουμε δύο δίκαιους αλγόριθμους χρονοπρογραμματισμού, τον Fair Completion Time (Ordering) και τον Fair Completion Time Estimation (Assignment). Κατόπιν τους υλοποιούμε και τους εξομοιώνουμε με το GridSim Toolkit και συγκρίνουμε την απόδοση τους με κλασικούς αλγόριθμους χρονοπρογραμματισμού. / The subject of this thesis is the implementation and simulation of fair scheduling algorithms applied on Computational Grids and their comparison with the classic scheduling algorithms. The basic idea of the Grid Technology and the services it provides, is the unification of computational and storage resources. This way it is possible to serve sophisticated applications, in fields like scientific research and trading. A Grid Network demands the sharing of the computational and storage resources, and high bandwidth connections between them. Scheduling algorithms are responsible for the efficient assignment of tasks to resources for better quality of service. Evaluating the efficiency of a scheduling algorithm depends on a utility function that we seek to optimize which in turns depends on techno-economic criteria. As a result of trying to optimize the utility function, some tasks with specific characteristics are favoured against others. A fair scheduling algorithm however should treat all tasks in the same way regardless of their characteristics. In this thesis we study the Fair Completion Time Ordering Algorithm and suggest a new fair scheduling algorithm called Fair Completion Time Estimation Assignment Algorithm. We implement and simulate these algorithms using the GridSim Toolkit and compare them with the classic scheduling algorithms.

No description available.

In this thesis morphologies, coarsening mechanisms and kinetics are examined in a systematic way, when phase separation and subsequent microstructural coarsening is modelled using deterministic mean field and stochastic Monte Carlo methods. For the mean field approach a microscopic diffusion equation due to Khachaturyan is employed, and a variation of it with an environment dependent mobility. Monte Carlo simulations are carried out with vacancy and Kawasaki dynamics, and a residence time algorithm is applied in the vacancy case. In mean field models microstructural evolution results from a direct minimization of a free energy functional, and the mechanism of atomic diffusion does not appear explicitly. In Monte Carlo models, changes in site occupancies are effected by direct exchanges of neighbouring atoms (Kawasaki dynamics), or through vacancy motion. In this thesis the correspondence between mean field and Monte Carlo models in describing phase transformations in binary alloys is examined. Several examples of cases in which these differences between deterministic and stochastic models affect the phase transformation are given, and the underlying differences are analyzed. It is also investigated how the choice of diffusion mechanism in the Monte Carlo model affects the microstructural evolution. Most Monte Carlo studies have been carried out with Kawasaki dynamics, although in real metals such direct exchanges are very unlikely to occur. It will be shown how the vacancy diffusion mechanism produces a variety of coarsening mechanisms over a range of temperatures, which the Kawasaki dynamics fails to capture. Consequently, kinetics and resulting morphologies, especially at low temperatures, are affected. Finally, the question of physicality of time scales in mean field and Monte Carlo models is addressed. Often a linear dependence between Monte Carlo time and real physical time is assumed, although there is no rigorous justifcation for this. In mean field models, time is defined through the atomic mobility. By examining the effect of a realistic diffusion mechanism in systems undergoing phase transformation, a critical discussion of time scales in microscopic mean field models and a Monte Carlo model with Kawasaki dynamics is presented.

Computational fluid dynamics (CFD) is a significant tool routinely used indesign and optimization in aerospace industry. Often cases with unsteadyflows must be computed, and the long compute times of standard methods hasmotivated the present work on new implicit methods to replace the standardexplicit schemes. The implementation and numerical experiments were donewith the Swedish national flow solver Edge, developed by FOI,universities, and collaboration partners.The work is concentrated on a Lower-Upper Symmetric Gauss-Seidel (LU-SGS)type of time stepping. For the very anisotropic grids needed forReynolds-Averaged Navier-Stokes (RANS) computations of turbulent boundary layers,LU-SGS is combined with a line-implicit technique.  The inviscid flux Jacobians which contribute to the diagonalblocks of the system matrix are based on a flux splitting method with upwind type dissipation giving  control over diagonal dominance and artificial dissipation.The method is  controlled by several parameters, and comprehensivenumerical experiments were carried out to identify their influence andinteraction so that close to optimal values can be suggested. As an example,the optimal number of iterations carried out in a time-step increases with increased resolution of the computational grid.The numbering of the unknowns is important, and the numberings produced by mesh generators of Delaunay- and advancing front-type wereamong the best.The solver has been parallelized with the Message Passing Interface (MPI) for runs on multi-processor hardware,and its performance scales with the number of processors at least asefficiently as the explicit methods. The new method saves typicallybetween 50 and 80 percent of the runtime, depending on the case, andthe largest computations have reached 110M grid nodes. Theclassical multigrid acceleration for 3D RANS simulations was foundineffective in the cases tested in combination with the LU-SGS solverusing optimal parameters. Finally, preliminary time-accurate simulations for unsteady flows have shown promising results. / <p>QC 20141201</p>

In this study molecular dynamics simulation program in NVT ensemble using Velocity Verlet integration was written in order to investigate the glass forming ability of two metallic systems. The Zn-Mg system, one of the frontiers of simple metal-metal metallic glasses and Fe-B, inquiring attention due to presence of many bulk glass forming alloy systems evolved from this binary with different alloying element additions. In addition to this, atomistic calculations on the basis of ordering were carried out for both Zn-Mg and Fe-B systems. Ordering energy values are calculated using electronic theory of alloys in pseudopotential approximation and elements which increase the ordering energy between atoms were determined. The elements which increase the ordering energy most were selected as candidate elements in order to design bulk amorphous alloy systems. In the experimental branch of the study centrifugal casting experiments were done in order to see the validity of atomistic calculations. Industrial low grade ferroboron was used as the master alloy and pure element additions were performed in order to constitute selected compositions. Fe62B21Mo5W2Zr6 alloy was successfully vitrified in bulk form using nearly conventional centrifugal casting processing. Specimens produced were characterized using SEM, XRD, and DSC in order to detect the amorphous structure and also the crystalline counterpart of the structure when the cooling rate is lower. Sequential peritectic and eutectic reaction pattern was found to be important for metallic glasses which can be vitrified in bulk forms with nearly conventional solidification methods.

Organizations have spent and continue to spend millions of dollars on information systems (IS) in order to enable business success. Information systems have long been used to help managers make better decisions, better understand the nature of customers and improve employee productivity. They have enabled transformations in organizations, such as simplification and acceleration of work processes, and contributed to continued improvement and innovation in these processes. It is not that easy however to make this simplification and acceleration of work processes to happen. A common problem is that individuals that are supposed to use these systems do not use them, and if an information system is to contribute to business success it has to be adopted and used. The question is therefore, how do we get individuals to adopt and use systems that are implemented? This dissertation focus on what influences individual adoption and use, and how we can get individuals to adopt and use systems that are implemented. The information system under investigation is an electronic ordering (e-ordering) system. E-ordering systems are used by individual end-users (requestors, authorizers and goods receivers) in an organization when ordering products and services. The system aims at contributing to reduced maverick (i.e. wild) purchases and increased compliance with a few centrally chosen suppliers, thus facilitating lower purchasing prices and a reduction of the costs for purchasing. The thesis also discusses the relative difficulty in getting individuals to continue to use the system compared to get them to adopt it. Another issue that is discussed is that the acceptance process does not have to happen gradually, it can instead happen in short spurts. It is further discussed what can influence these spurts. / Diss. Stockholm : Handelshögskolan, 2009 Sammanfattning jämte 5 uppsatser

Les composés en couches avec des ions métaux de transition ont leur bande de conduction dans les orbitales d. On se concentrera dans cette thèse sur les systèmes où le champs cristallin sépare les orbitales en deux sets dégénérés, t2g et eg, où les électrons de conduction sont sur les orbitales eg. C'est le cas pour les dichalcogénures en couches à métaux de transitions et 2H-AgNiO2 qui sont connus pour présenter des ordres de charge, un arrangement périodique des électrons sur le réseau. Les dichalcogénures en couches à métaux de transitions ont divers motifs, des ordres des charge commensurables et incommensurables, parmi eux, des ordres de charge à grande maille unité,comme le motif √13x√13 en étoile de David. 2H-AgNiO2 a un ordre de charge triple mais reste métallique.Dans le but de comprendre leurs ordres de charge, nous avons établi un modèle de Hubbard étendu multibandes et nous avons recentré notre intérêt sur les orbitales eg avec fortes interactions coulombiennes locales. À l'aide d'une approche en liaison forte et de considérations électrostatiques, puis grâce à la méthode de Hartree-Fock non restreinte, nous avons construit le diagramme de phases en fonction de la force des interactions coulombiennes, aussi bien locale qu'à courte portée, et nous avons fait évoluer la structure de bande en utilisant le ratio libre t'/t qui décrit la structure de bande dans les matériaux ayant des orbitales eg. Nous avons révélé un diagramme de phase riche avec plus de dix phases où certaines transitions peuvent être contrôlées par la structure de bande. En particulier, nous avons trouvé des phases pinball liquid, un ordre de charge métallique à trois sites par maille unité, où des charges localisées (pins) sont entourées de charges itinérantes (balls) sur un réseau hexagonal. Des ordres de charges à grande maille unité sont aussi stabilisés, tels que des ordres de charge et d'orbitale incommensurables et un ordre de charge √12x√12, qui rappelle le motif √13x√13 en étoile de David présent dans 1T-TaS2. Ces états électroniques s'avèrent génériques pour le réseau triangulaire demi rempli et sont aussi trouvés dans le cas isotrope, qui correspond au modèle de Hubbard étendu à une bande.Cependant, la méthode de Hartree-Fock non restreinte est problématique pou saisir les propriétés des phases lors d'une forte anisotropie de la structure de bande pour les états de Mott. Pour résoudre ce problème, nous avons établi un hamiltonien type Heisenberg à partir d'une théorie de perturbation. Ensuite, nous avons établit le diagramme de phases de ce nouvel hamiltonien en utilisant une approche classique et la diagonalisation exacte avec une analyse de symétries et l'algorithme de Lanczos pour un système de 24 sites. Mis à part les phases connues du modèle de Heisenberg en présence d'un champ magnétique, les configuration Y et V, le plateau 1/3, la phase ferro-orbitale, l'anisotropie de la structure de bande des orbitales eg conduit à d'autres ordres avec une composante τy ou τx et τz finies, différents ordres en bande et des ondes de densité d'orbitales. / Layered compounds are materials which exhibit charge order and novel phase of matter. This is the case in layered transition metal compounds, which have their band conduction on d-orbitals, a key ingredient to understand their electronic properties. We will focus in this dissertation on systems where the crystal-field splits orbitals into two degenerate subsets, t2g and eg, and where conduction electrons are on eg-orbitals. It is the case for layered transition-metal dichalcogenides and 2H-AgNiO2, which are known to exhibit charge orders, a periodic arrangement of electrons on the lattice. Layered transition-metal dichalcogenides have various pattern, incommensurate or commensurate insulating charge orders, among them large-unit cells charge orders. 2H-AgNiO2 have a charge order but is yet metallic.In order to investigate their charge orders, we derive a generic multiorbital extended Hubbard model and we refine our interest to eg-orbital with strong local Coulomb interactions. With a tight binding approach and electrostatic considerations, then the unrestricted Hartree-Fock method, we build the phase diagrams as a function of the strength of the Coulomb interactions, local and short-range, and we tun the band structure using the ratio $t'/t$ of the $e_g$-orbitals. We unravel a rich phase diagram with more than ten phases where some transitions can be controlled by the band structure. In particular, we found pinball liquid phases, metallic threefold charge orders where localized charges (pins) are surrounded by itinerant charges (balls) on a honeycomb lattice. Phases with large unit-cells are also stabilized, such as incommensurate charge and orbital orders and a √12x√12 charge order. These electronic states are generic for the half-filled triangular lattice and are also found in the isotropic limit, which corresponds to the single-band spinful extended Hubbard model.To capture the properties of phases with strong band structure anisotropy in the Mott state, that unrestricted Hartree-Fock fails to capture, we derived a Heisenberg-like Hamiltonian from perturbation theory. Then, we build the phase diagram of this new effective Hamiltonian using a classical approach and exact diagonalization with a symmetry analysis and Lanczos algorithm for a 24-site cluster. Apart from the known phases of the Heisenberg model in presence of a field, the Y and V configuration, the 1/3 plateau, the ferro-orbital phase, the anisotropy of the band structure of eg-orbitals leads to other ordering with finite τy or τx and τz components, different stripe orders and orbital density waves. We build a rich phase diagram from this new Hamiltonian.

abstract: This thesis aims to investigate the capacity and bit error rate (BER) performance of multi-user diversity systems with random number of users and considers its application to cognitive radio systems. Ergodic capacity, normalized capacity, outage capacity, and average bit error rate metrics are studied. It has been found that the randomization of the number of users will reduce the ergodic capacity. A stochastic ordering framework is adopted to order user distributions, for example, Laplace transform ordering. The ergodic capacity under different user distributions will follow their corresponding Laplace transform order. The scaling law of ergodic capacity with mean number of users under Poisson and negative binomial user distributions are studied for large mean number of users and these two random distributions are ordered in Laplace transform ordering sense. The ergodic capacity per user is defined and is shown to increase when the total number of users is randomized, which is the opposite to the case of unnormalized ergodic capacity metric. Outage probability under slow fading is also considered and shown to decrease when the total number of users is randomized. The bit error rate (BER) in a general multi-user diversity system has a completely monotonic derivative, which implies that, according to the Jensen's inequality, the randomization of the total number of users will decrease the average BER performance. The special case of Poisson number of users and Rayleigh fading is studied. Combining with the knowledge of regular variation, the average BER is shown to achieve tightness in the Jensen's inequality. This is followed by the extension to the negative binomial number of users, for which the BER is derived and shown to be decreasing in the number of users. A single primary user cognitive radio system with multi-user diversity at the secondary users is proposed. Comparing to the general multi-user diversity system, there exists an interference constraint between secondary and primary users, which is independent of the secondary users' transmission. The secondary user with high- est transmitted SNR which also satisfies the interference constraint is selected to communicate. The active number of secondary users is a binomial random variable. This is then followed by a derivation of the scaling law of the ergodic capacity with mean number of users and the closed form expression of average BER under this situation. The ergodic capacity under binomial user distribution is shown to outperform the Poisson case. Monte-Carlo simulations are used to supplement our analytical results and compare the performance of different user distributions. / Dissertation/Thesis / M.S. Electrical Engineering 2012

Este trabalho tem como objetivo buscar subsídios na concepção de polissemia da Semântica Cognitiva para auxiliar na disposição das acepções de itens lexicais polissêmicos em learner’s dictionaries. Para tanto, ele, inicialmente, analisa de que forma os quatro principais dicionários que compreendem esse genótipo – CALD (2008), COBUILD (2006), LDCE (2009) e OALD (2005) – apresentam suas acepções, considerando duas variáveis: (i) o emprego de uma solução homonímica ou polissêmica para a estruturação dos verbetes e (ii) a divisão e ordenação das acepções. A partir das análises, percebe-se que a solução empregada por essas obras varia, havendo a adoção tanto da solução polissêmica, com e sem divisão interna nos verbetes, quanto da solução homonímica, por critério morfológico e semântico. Quanto às acepções, por um lado, as formas como os dicionários dividem e relacionam os significados são diferentes e, por outro, os critérios utilizados pelas obras para a ordenação das acepções não se mostram plenamente satisfatórios, pois algumas delas não explicitam quais critérios são empregados na ordenação das acepções e a utilização do mesmo critério (de frequência) por diferentes obras gera resultados distintos. Além disso, para que a frequência pudesse ser empregada como critério objetivo, seria necessária a delimitação de parâmetros quantitativos ainda não disponíveis. A seguir, são levantadas questões teórico-metodológicas que surgem ao abordar a organização microestrutural, destacando que a discussão da ordenação das acepções nos dicionários é dependente de outras variáveis, como sua vinculação a uma teoria do significado lexical e da definição lexicográfica. Por fim, o trabalho busca delimitar quais das características da visão prototípica de estrutura lexical podem ser transpostas ao âmbito lexicográfico para lidar com o problema da representação da polissemia nos learner’s dictionaries.Apresentam-se propostas de verbetes criados com base em critérios estabelecidos por nós para a transposição das noções semântico-cognitivas para a ordenação das acepções. / In this thesis, we aim at contributing to sense ordering of polysemous lexical items in learner‘s dictionaries based on the conception of polysemy as developed by Cognitive Semantics. First we analyze in which way the four main dictionaries known under the label of learner‘s dictionary present their senses – CALD (2008), COBUILD (2006), LDCE (2009) e OALD (2005). We consider two variables in this analysis: (i) the use of a homonymic or a polysemous solution for structuring the entry and (ii) the sense division and ordering. From the analysis, we find out that the solutions applied in the dictionaries vary, for they adopt both a polysemous solution, with and without a division within the entry, and a homonymic solution, through morphological and semantic criteria. Regarding the senses, on the one hand, the way the dictionaries split and relate them is different. On the other hand, the criteria used in the dictionaries for ordering senses showed to be unsatisfactory, because some of the works do not explicit which criteria they apply in sense ordering, and because the use of the same criterion (frequency) in different dictionaries yields distinct results. Moreover, in order to use frequency as an objective criterion, the definition of quantitative parameters, which are still not available, would be made necessary. Hereafter, we discuss theoretical-methodological issues raised when it comes to sense ordering: this microstructural organization is dependent upon other variables, such as its relation to a theory of word meaning and a theory of lexicographical definition. At the end of this work, we present the characteristics of the prototypical conception of lexical structure that could be applied to lexicography to deal with the problem of representing polysemy in learner‘s dictionaries. We, then, propose some entries developed according to criteria we established in order to use cognitive semantic notions in sense arrangement.