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Machine-to-machine communication congestion mechanism / Mécanisme de congestion en M2M communicationEl Fawal, Ahmad Hani 03 December 2018 (has links)
Nos travaux s’orientent vers les problèmes de réseaux sans fil liés à la coexistence des communications machine-to-machine (M2M) et humain-humain (H2H). On souhaite souligner l'impact mutuel entre les trafics M2M et H2H dans un contexte d’Internet des objets (IoT : Internet Of Things) en particulier lors des catastrophes. Les communications M2M, qui devraient connaître une roissance exponentielle dans un avenir proche, constitueront un facteur important pour affecter tous les réseaux mobiles. On prévoit un grand nombre d'appareils M2M qui entraînera inévitablement des problèmes de saturation et aura des impacts remarquables sur les trafics, les services et les applications M2M et H2H. Pour étudier les influences mutuelles M2M et H2H, nous développons un nouveau modèle markovien à temps continu (CTMC) pour simuler, analyser et mesurer les différentes stratégies d'accès aux réseaux sans fil. Notre modèle nous a permis de contourner certaines limitations des simulateurs professionnels de LTE-A (Long Term Evolution-Advanced) comme SimuLTE en terme d’un nombre massif d'appareils M2M, une flexibilité de certains paramètres ou pour élaborer plus des outils statistiques. Lors d’un sinistre et suite à un énorme nombre de M2M souhaitant accéder aux réseaux sans-fil, nous avons constaté un épuisement rapide de la bande passante allouée dans les réseaux LTE-M (Long Term Evolution for Machines) ou Narrow Band for IoT (NB-IoT). Pour résoudre ce problème, nous proposons une nouvelle approche appelée Adaptive eNodeB (A-eNB) pour les réseaux LTE-M et NB-IoT. Selon nos simulations, l’A-eNB peut résoudre progressivement le problème de surcharge tout en assurant une satisfaisante qualité de service (QoS) pour le trafic H2H. Avec le concept d’A-eNB, un réseau LTE-M pourra adapter ses ressources pour faire face à une augmentation progressive du nombre de connexions M2M accédant au réseau LTE-M / NB-IoT et en même temps réduire l'impact sur le trafic H2H. / This Ph.D. work aims to study the Machine-to-Machine (M2M) congestion overload problem and the mutual impact among M2M and Human-to-Human (H2H) traffics in IoT (Internet of Things) environments specifically during disaster events. M2M devices with their expected exponential booming in the near future, will be one of the significant factors to influence all mobile networks. Inevitably, the expected huge number of M2M devices causes saturation problems, and leads to remarkable impacts on both M2M and H2H traffics, services and applications. To study the M2M and H2H mutual influences, we create a new platform model based on Continuous-Time Markov Chain (CTMC) to simulate, analyze and measure radio access strategies due to the limitations of existing Long Term Evolution-Advanced (LTE-A) simulators (i.e, SimuLTE) in term of massive M2M devices, parameter flexibility and statistical tools. Additionally, during disaster events, a fast bandwidth depletion of the limited bandwidth assigned to M2M devices in Long Term Evolution for Machines (LTE-M) and Narrow Band for IoT (NB-IoT) networks is expected due to the high arrival request of M2M device network access. To address this problem, we propose a new approach named Adaptive eNodeB (A-eNB) for both LTE-M and NB-IoT networks. The A-eNB can solve gradually the overload problem, while keeping the H2H traffic Quality of Service (QoS) not to be affected badly. The network adaptation is provided through a dynamic LTE-M resource reservation aiming to increase the number of M2M connections accessing the LTE-M/NB-IoT network and to decrease the impact on H2H traffic.
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Emisión electrónica e intercambio de carga en procesos de colisión de iones con blancos moleculares de interés biológicoBachi, Nicolás 05 July 2023 (has links)
Esta tesis doctoral refiere al estudio de colisiones inelásticas entre iones y
blancos de interés biológico, en un rango intermedio y alto de energías de
impacto.
Uno de los mayores desafíos del presente trabajo fue incorporar la correlación
electrónica de manera explícita durante todo el proceso de colisión. Es por
ello que la metodología elegida para realizar este estudio fue el Método de
Trayectorias Clásicas Monte Carlo (CTMC), en la cuál es factible introducir de
manera parcial la correlación electrón-electrón en sistemas multielectrónicos
y, en consecuencia, determinar el papel que desempeña esta interacción
en los procesos de remoción electrónica múltiple, tales como la ionización
múltiple o la ionización con transferencia de carga.
Sin embargo, una de las mayores limitaciones que presenta un tratamiento
clásico es la autoionización de manera espuria de un blanco multielectrónico
por efecto de la correlación electrónica. Para evitar este problema, en una
primera etapa, se han implementado extensiones del método CTMC en
colisiones de iones sobre He, a fin de evaluar el desempeño de distintos
potenciales estabilizadores propuestos en la literatura.
En función de la experiencia adquirida, se procedió a modelar colisiones
de iones sobre moléculas de H2O. Este modelo se destaca por el hecho de
que considera los electrones de valencia, así como también su estructura de
equilibrio durante todo el proceso de colisión. Los resultados obtenidos han
permitido analizar el rol que desempeña el proceso de ionización múltiple en
la producción electrónica, y han servido de base para modelar colisiones con
sistemas de interés en hadronterapia, como puede ser el caso de la molécula
de uracilo.
Las predicciones producidas por estos modelos para los procesos de ionización
se han evaluado en términos de secciones eficaces a niveles total y diferencial
(tanto simple como doble) y se han contrastado con los datos experimentales
y resultados teóricos reportados en la literatura. / This work refers to the study of inelastic collisions between ions and biological
targets, at an intermediate to high-impact energy range.
One of the greatest challenges of this work was to explicitly incorporate
the interelectronic correlation throughout the collision process. Therefore,
the methodology chosen to perform this study was the Classical Trajectory
Monte Carlo method (CTMC), in which it is possible to partially introduce
electron-electron correlation in multi-electronic systems and, consequently,
determine the role that this interaction plays in multiple electron removal
processes, such as multiple ionization or transfer ionization.
However, one of the greatest limitations of a classical treatment is the spu-
rious autoionization of a multi-electronic target due to electronic correlation.
To avoid this problem, in the first stage, extensions of the CTMC method
have been implemented in ion-He collisions to evaluate the performance of
different stabilizing potentials proposed in the literature.
Based on the acquired experience, ion-H2O collisions were modeled. This
model stands out because it considers valence electrons, as well as their equi-
librium structure throughout the collision process. The obtained results have
allowed us to analyze the role played by the multiple ionization processes in
electronic production and have served as the basis for modeling collisions
with systems of interest in hadrontherapy, such as the uracil molecule.
The predictions produced by these models of the ionization processes have
been evaluated in terms of total and differential cross sections (simple and
double) and they have been compared to experimental data and theoretical
results reported in the literature.
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Modelado CTMC de blancos atómicos y moleculares relevantes en física de colisiones por impacto de ionesCariatore, Nelson Daniel 25 November 2015 (has links)
En esta tesis, se han desarrollado diversos estudios de captura electrónica
por iones colisionando sobre atómos y moléculas bajo el método
de trayectorias clásicas Monte Carlo (CTMC). El objetivo central del
trabajo consistió en mejorar la descripción del blanco, ya que se ha
demostrado en la literatura que una correcta descripción del blanco
es importante a la hora de obtener secciones eficaces precisas.
El estudio se ha enfocado en procesos de captura electrónica selectiva
para el rango de energías bajas e intermedias de colisión. Se calcularon
las secciones eficaces totales, las secciones eficaces de captura electrónica
selectiva y las secciones eficaces de líneas de emisión fotónica que
provienen del decaimiento radiativo que le siguen a los procesos de
captura electrónica a estados excitados del proyectil.
Las investigaciones realizadas son relevantes desde el punto de vista
de lograr un mejor entendimiento de los mecanismos físicos que
median en los procesos de colisiones, principalmente en el canal de
captura electrónica. Asimismo, las secciones eficaces calculadas son
una herramienta necesaria en diversas áreas de la física aplicada. Las
secciones eficaces calculadas en esta tesis tienen especial relevancia en
el diagnóstico de plasma en los reactores de energía por fusión y en
astrofísica, puntualmente en colisiones entre los iones del viento solar
y los gases en la coma de cometas o en atmósferas planetarias.
Se presentan secciones eficaces totales de intercambio de carga y secciones
eficaces de captura a estados selectivos y se comparan con las
obtenidas por diferentes métodos teóricos, así como con datos experimentales
presentados por de diferentes laboratorios del mundo. / In this thesis, electron capture processes in ion collisions with atoms
and molecules have been studied by means of the classical trajectory
Monte Carlo (CTMC) method. The main objective of this work was to
improve the description of target, provided that a correct description
of the target has shown to be essential in order to obtain accurate
cross sections.
The study has been focused on state–selective electron–capture processes
for low to intermediate impact energies. Present calculations
involve total cross sections, state–selective cross sections and photon–
emission–lines cross sections which originate in the radiative decay
that follow electron capture to excited states of the projectile.
The investigations carried out are relevant in order to identify the
physical mechanisms which mediate collisions processes leading to
electron capture channel. Besides, theoretical cross sections are a necessary
tool for applied physics. The cross sections calculated in this
thesis are relevant to plasma diagnostics in fusion power reactors and
in astrophysics, specifically in collisions between solar wind ions and
cometary particles and planetary atmospheres.
Total and state–selective charge–exchange cross sections are presented
and compared to those obtained by other different theoretical methods
as well as to experimental data from different laboratories worldwide.
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Avaliação da disponibilidade de video surveillance as service (VSAAS)MÁGNO, Carlos 04 September 2015 (has links)
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Previous issue date: 2015-09-04 / CNPq / Nos últimos anos, sistemas de Video Surveillance as a Service (VSaaS) apresentam
um aumento significativo na demanda por técnicas de segurança que elevem os níveis de
confiabilidade do serviço. Em paralelo, o paradigma de Computação em Nuvem tornou-se uma
importante ferramenta para serviços remotos da computação. O VSaaS entrega armazenamento
de grande quantidade de dados. Em 2012, 50% do armazenamento em big data que necessitou
serem analisados foram de vídeo de vigilância. Em geral, os vídeos têm um alto significado para
seus proprietários, não permitindo longos períodos de interrupção. Com o objetivo de evitar
baixos desempenhos e ampliar a qualidade dos serviços de vídeo são necessários mecanismos
para garantir alta disponibilidade em VSaaS. Entretanto, esta tarefa é difícil sem gerar impacto
no custo. O presente trabalho propõe dois sistemas de VSaaS que foram submetidos a análise
de disponibilidade, por meio de modelos analíticos (RBD, CTMC e SPN). O primeiro sistema,
denominado doméstico, foi caracterizado pelos elementos essenciais para uma estrutura básica do
VSaaS para ser utilizado em casas e pequenos comércios. Estes sistemas geraram três arquiteturas
que foram modeladas para a obtenção de fórmulas fechadas, elas são importantes para realização
de análises. O modelo da arquitetura 1 foi validado e as outras arquiteturas variaram dessas. A
arquitetura 3 teve a maior disponibilidade entre as outras arquiteturas, por possuir a quantidade
maior de componentes replicados. O downtime (em horas) desta arquitetura comparada com a
sem replicações foi em 36,89%. Por ela ter a maior disponibilidade, foi realizada uma análise
de sensibilidade que mostrou o componente “Node” como o de maior impacto. No segundo
sistema, foi apresentado um VSaaS de uma empresa, chamado empresarial, gerando 18 (dezoito)
arquiteturas, uma delas comparada a arquitetura A1 (sem redundância), obteve uma redução
significativa do downtime de 30% com um pequeno aumento no custo na ordem de 7%. Caso
um determinado serviço exija um downtime menor, outra análise apontou uma arquitetura com
redução de 80% ao aumentar 30% do custo. Diante desse panorama foram propostas e analisadas
arquiteturas que podem auxiliar administradores a tomar importantes decisões na implementação
de VSaaS. / In the last few years, Video Surveillance as a Service VSaaS has shown the significant
increase in demand for security mechanisms to ensure reliability higher levels. In parallel, the
Cloud Computing paradigm has become an important tool for remote computing services. VSaaS,
for example, allows for storage large amounts of data. In 2012, 50% of big data storage were
surveillance video and in general, videos have a high significance for their owners, not allowing
long periods interruption. To avoid video services with low performance and increase the quality,
mechanisms to ensure high availability in VSaaS are required. However, this task is difficult
without generating a major impact on cost, so this paper proposes two VSaaS systems who
underwent an availability analysis, using analytical models (RBD, CTMC, and SPN). The first
system, entitled domestic, was characterized by essential elements of a basic structure VSaaS, for
use in homes and small businesses. This system generated three architectures that were modeled
to obtain closed formulas; they are important to performing analyzes. The model architecture
one was validated, and other architectures vary these. The architecture three had the highest
availability of the other architectures, by owning the largest number of replicated components.
The downtime (in hours) this architecture compared to a without replication was 36.89%. For
having the highest availability, a sensitivity analysis showed the "Node"component as the most
relevant. In the second system, was showed a VSaaS in a company and has generated eighteen
architectures. One of them compared to a baseline, we obtained a significant reduction in
downtime (30%) and a small increase in cost (on the order of 7%). In case, of the service requires
less downtime, another analysis pointed an architecture with a reduction 80% of downtime and
increased 30% in the cost. We propose and analyze architectures that can help administrators
make important decisions in the VSaaS implementation.
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Continuous Approximations of Discrete Phylogenetic Migration ModelsHuss, Simon, Mosetti Björk, Theodor January 2024 (has links)
Phylogenetics explores the evolutionary relationships among species and one of the main approaches is to construct phylogenetic trees through inference-based methods. Beyond the evolutionary insights these trees provide, the underlying tree structure can also be used to study geographical migration of species. These geographical models, reminiscent of models of DNA sequence evolution, have predominantly been discrete in their nature. However, this poses a multitude of challenges, especially with high-dimensional state-spaces. Previous work has explored the possibility of using continuous diffusion models for geographical migration, however these were not aiming to model non-local migration and large state-spaces. This paper presents and evaluates a scalable continuous phylogenetic migration model which aims to approximate conventional discrete migration models in the case of local and non-local migration.
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Scalable analysis of stochastic process algebra modelsTribastone, Mirco January 2010 (has links)
The performance modelling of large-scale systems using discrete-state approaches is fundamentally hampered by the well-known problem of state-space explosion, which causes exponential growth of the reachable state space as a function of the number of the components which constitute the model. Because they are mapped onto continuous-time Markov chains (CTMCs), models described in the stochastic process algebra PEPA are no exception. This thesis presents a deterministic continuous-state semantics of PEPA which employs ordinary differential equations (ODEs) as the underlying mathematics for the performance evaluation. This is suitable for models consisting of large numbers of replicated components, as the ODE problem size is insensitive to the actual population levels of the system under study. Furthermore, the ODE is given an interpretation as the fluid limit of a properly defined CTMC model when the initial population levels go to infinity. This framework allows the use of existing results which give error bounds to assess the quality of the differential approximation. The computation of performance indices such as throughput, utilisation, and average response time are interpreted deterministically as functions of the ODE solution and are related to corresponding reward structures in the Markovian setting. The differential interpretation of PEPA provides a framework that is conceptually analogous to established approximation methods in queueing networks based on meanvalue analysis, as both approaches aim at reducing the computational cost of the analysis by providing estimates for the expected values of the performance metrics of interest. The relationship between these two techniques is examined in more detail in a comparison between PEPA and the Layered Queueing Network (LQN) model. General patterns of translation of LQN elements into corresponding PEPA components are applied to a substantial case study of a distributed computer system. This model is analysed using stochastic simulation to gauge the soundness of the translation. Furthermore, it is subjected to a series of numerical tests to compare execution runtimes and accuracy of the PEPA differential analysis against the LQN mean-value approximation method. Finally, this thesis discusses the major elements concerning the development of a software toolkit, the PEPA Eclipse Plug-in, which offers a comprehensive modelling environment for PEPA, including modules for static analysis, explicit state-space exploration, numerical solution of the steady-state equilibrium of the Markov chain, stochastic simulation, the differential analysis approach herein presented, and a graphical framework for model editing and visualisation of performance evaluation results.
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A metapopulation model for mass gatherings Application: global travel, Hajj and the spread of measlesMenjivar, Liliana 12 September 2013 (has links)
Mass gatherings stress local and global health care systems as they bring together individuals from all over the world that have very different health conditions. We firstly provide an overview of the concepts and results of mathematical epidemiology and public health. Secondly, we present an introduction to the mathematical modelling of measles using deterministic and stochastic approaches for both single and multiple populations. Lastly, we develop a model for mass gatherings and present an application to measles during the Hajj by studying an SIR deterministic metapopulation model with residency and its stochastic analogue. The models incorporate real world country data and time dependent movement and transmission rates, accounting for realistic volume of international travel and seasonality of measles activity. Numerical results for the deterministic system are presented. We conclude with a discussion on further work.
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A metapopulation model for mass gatherings Application: global travel, Hajj and the spread of measlesMenjivar, Liliana 12 September 2013 (has links)
Mass gatherings stress local and global health care systems as they bring together individuals from all over the world that have very different health conditions. We firstly provide an overview of the concepts and results of mathematical epidemiology and public health. Secondly, we present an introduction to the mathematical modelling of measles using deterministic and stochastic approaches for both single and multiple populations. Lastly, we develop a model for mass gatherings and present an application to measles during the Hajj by studying an SIR deterministic metapopulation model with residency and its stochastic analogue. The models incorporate real world country data and time dependent movement and transmission rates, accounting for realistic volume of international travel and seasonality of measles activity. Numerical results for the deterministic system are presented. We conclude with a discussion on further work.
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Development of Monte Carlo track structure simulations for protons and carbon ions in waterLiamsuwan, Thiansin January 2012 (has links)
The goal of radiation therapy is to eradicate tumour cells while minimising radiation dose to healthy tissues. Ions including protons and carbon ions have gained increasing interest for cancer treatment. Advantages of ion beam therapy are conformal dose distribution, and for ions heavier than protons increased biological effectiveness in cell killing, compared to conventional radiation therapy using photons. Despite these advantages, fundamental problems in ion beam therapy include accuracy of dose determination at the cellular level, and characterisation of the radiation quality at the microscopic scale. Due to the high density of interactions along ion tracks, inhomogeneity of dose and track parameters at the cellular level is one of the major concerns for ion beam therapy. The aim of the thesis is to develop computational tools for dosimetry of ion tracks at the molecular level. Event-by-event Monte Carlo track structure (MCTS) simulations were developed for full-slowing-down tracks of protons and carbon ions in water representing cellular environment. In Paper I, the extension of the MCTS code KURBUC_proton was carried out to energies up to 300 MeV, covering the entire proton energy range used in radiation therapy. Physical properties and microdosimetry of proton tracks were investigated and benchmarked with the experimental data. Papers II-V describe the development of the MCTS code for full-slowing-down tracks of carbon ions. In Papers II-IV, the classical trajectory Monte Carlo (CTMC) model was developed for the calculation of interaction cross sections for low and intermediate energy carbon projectiles of all charge states (C0 to C6+) in water. In Paper V, the calculated cross sections were implemented in a new MCTS code KURBUC_carbon simulating carbon ions of energies 1-104 keV/u in water. This development allows the investigation of track parameters in the Bragg peak region of carbon ion beams. Publication of the thesis and the published papers make contribution to the physics of ion interactions in matter, and provide a new and complete database of electronic interaction cross sections for low and intermediate energy carbon projectiles of all charge states in water. The MCTS codes for protons and carbon ions provide new tools for biophysical study, including microdosimetry, of ion tracks at cellular and subcellular levels, in particular in the Bragg peak region of these ions. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted.</p><p> </p>
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Adaption of Akaike Information Criterion Under Least Squares Frameworks for Comparison of Stochastic ModelsBanks, H. T., Joyner, Michele L. 01 January 2019 (has links)
In this paper, we examine the feasibility of extending the Akaike information criterion (AIC) for deterministic systems as a potential model selection criteria for stochastic models. We discuss the implementation method for three different classes of stochastic models: continuous time Markov chains (CTMC), stochastic differential equations (SDE), and random differential equations (RDE). The effectiveness and limitations of implementing the AIC for comparison of stochastic models is demonstrated using simulated data from the three types of models and then applied to experimental longitudinal growth data for algae.
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