Rozprawy doktorskie na temat „Dynamic Priority”

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.
Includes bibliographical references (p. 113-116).
by Himal P. Karmacharya.
M.Eng.

Energy consumption is increasingly affecting battery life and cooling for real- time systems. Dynamic Voltage and frequency Scaling (DVS) has been shown to substantially reduce the energy consumption of uniprocessor real-time systems. It is worthwhile to extend the efficient DVS scheduling algorithms to distributed system with dependent tasks. The dissertation describes how to extend several effective uniprocessor DVS schedul- ing algorithms to distributed system with dependent task set. Task assignment and deadline assignment heuristics are proposed and compared with existing heuristics concerning energy-conserving performance. An admission test and a deadline com- putation algorithm are presented in the dissertation for dynamic task set to accept the arriving task in a DVS scheduled real-time system. Simulations show that an effective distributed DVS scheduling is capable of saving as much as 89% of energy that would be consumed without using DVS scheduling. It is also shown that task assignment and deadline assignment affect the energy- conserving performance of DVS scheduling algorithms. For some aggressive DVS scheduling algorithms, however, the effect of task assignment is negligible. The ad- mission test accept over 80% of tasks that can be accepted by a non-DVS scheduler to a DVS scheduled real-time system.

Sandvik IT Services (SITS) ambition is to provide a smooth and suitable IT environment for the whole Sandvik organization. The idea is that SITS should provide end-to-end solutions globally in an efficient manner. To ensure that they can provide this, they have to be efficient in their work. To handle problems regarding incident and support, they have a large TV screen that shows important information about different processes. The demand for the information has increased; therefore the information displayed on the screen has also increased. Today, the amount of information on the screen is too big and it makes the information difficult to read and absorb. This work will help make SITS application management more effective in the future. Through Workshops for both managers and developers, it is necessary to find out the difference of what SITS requires to diversify priority information. And also be able to view the information in a user-friendly way, a layout of the information is suggested. The result of this work is to produce a design proposal.

Future wireless systems will have to support multimedia services such as voice, data and video. Issues in providing multimedia services on wireless systems include multiple access, bandwidth rationing, scheduling and power control. In this thesis, we address the last issue. CDMA is assumed to be the access method. Each of these services has different Quality of Service (QoS) requirements, maximum power and packet time-out constraints; in order to achieve the required QoS, they can alter their transmission. In this work, we present a novel Power Control With Priority Scheduling (PCWPS) algorithm for a wireless CDMA system, which achieves reliability and efficiently control packet loss due to timeout violation for simultaneously transmitted multimedia traffic, as well as minimizing system total interference. Our power control algorithm requires information about each traffic class instant state, as well as the wireless channel condition at the beginning power update iteration. Based on this information, the optimum allocated power can be calculated through linear or nonlinear programming methods. The simulation results show that our algorithm achieves good performance in term of packet loss due to timeout.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Este trabalho investiga o comportamento de métodos de alocação de canais para Sistemas Móveis Celulares quando associados ao uso de canais de guarda para priorizar chamadas que estejam em handoff. O objetivo desta associação é uma maior qualidade da ligação comparada à obtida quando não se faz uso dessa técnica. Resultados de simulações mostram que este objetivo pode ser atingido.
This work investigates the behavior of channel allocation schemes for Mobile Cellular Systems, when associated with channel guards giving priority to calls that are in handoff procedure. The objective of this association is a better call quality compared to the one in which this technique is not used. Simulation results show that indeed this can be achieved.

As terascale supercomputers become more common, and as the high-performance computing community turns its attention to petascale machines, the challenge of providing effective resource management for high-end machines grows in both importance and difficulty. These computing resources are by definition expensive, so the cost of underutilization is also high, e.g., wasting 5% of the compute nodes on a 10,000 node cluster is a much more serious problem than on a 100 node cluster. Moreover, the high energy and cooling costs incurred in maintaining these high end machines (often millions of dollars per year) can be justified only when these machines are used to their full capacity. On large clusters, conventional jobs schedulers are hard-pressed to achieve over 90% utilization with typical job-mixes. A fundamental problem is that most conventional parallel job schedulers only support static scheduling, so that the number of processors allocated to an application cannot be changed at runtime. As a result, it is common to see jobs stuck in the queue because they require just a few more processors than are currently available, resulting in long queue wait times for applications and low overall system utilization. A more flexible and effective approach is to support dynamic resource management and scheduling, where the number of processors allocated to jobs can be expanded or contracted at runtime. This is the focus of this dissertation --- dynamic resizing of parallel applications. Dynamic resizing significantly improves individual application turn-around time and helps the scheduler to achieve higher machine utilization and job throughput. This dissertation focuses on the potential benefits and challenges of dynamic resizing using ReSHAPE, a new framework for dynamic Resizing and Scheduling of Homogeneous Applications in a Parallel Environment. It also details several interesting and effective scheduling policies implemented in ReSHAPE and demonstrates their effectiveness to improve overall cluster utilization and individual application turn-around time.
Ph. D.

The Internet has become one of the most widely used forms of communication available. Many applications used on the Internet require the user to interact constantly with the network. For example web browsing where the user will expect the browser to respond quickly, to finish loading pages quickly and to do all of this at an equal level for all users. The network's performance is dependant on the protocols it uses and how the resources of the network are distributed. This is why TCP (Transmission Control Protocol) is one of the most important protocols, because it controls the amount of data entering the network and provides reliability to most interactive applications. The thesis starts by introducing a basic TCP model which is later extended to model the effects of burstiness produced by TCP. Burstiness can cause a routers buffer to unnecessarily overflow. These overflows cause TCP connections to under-utilise link bandwidth because of unnecessary packet retransmissions. A model to define a quantitative measure of both burstiness and throughput of a system of TCP connections is introduced. The model gives insight into how the TCP protocol causes burstiness and can be used to find scenarios where burstiness is decreased. This helps to improve the utilization of links by reducing the burstiness of protocols. An important performance metric for interactive traffic is user perceived delay, the delay that an end user would encounter when using an application. An example of user perceived delay is the time a user waits before a HTML web page starts loading. The retransmission delays are the most important type of delay for interactive traffic because they are usually very large. A dynamic priority RED Queue (DPRQ) is introduced which changes the priority of the queues based on the goodput (throughput of succesfully transmitted packets) threshold of the interactive traffic. Using dynamic priority allows packet loss to be reduced by up to eight times for interactive traffic, which intern reduces retransmission delay. Fairness measures how equally network resources are allocated amongst different connections. When a link with TCP connections is overloaded each connection on the link will reduce its throughput to allow all the connections to have approximately equal load. This does not take into account that other links may be under utilized. The fairness issue is addressed by introducing Multipath TCP (MATCP) which allows path selection to occur at the TCP layer. This allows each unique flow to take a different path, instead of all the flows of one source using the same path. Using MATCP, a finer grain of load-balancing can be achieved and the complexity and state required in the network is greatly reduced. Two analytic models are provided in chapters three and four, which investigate slow start and TCP burstiness. In chapter five the DPRQ queue is introduced to reduce user perceived delay. An analytic model of the DPRQ is provided and verified through experimental simulation. In chapter six an analytic model of Multipath TCP is provided, which is also verified by simulation.

According to the Federal Communications Commission's rules and recommendations set forth for the 3.5 GHz Citizens Broadband Radio Service, a three-tiered structure shall govern the newly established shared wireless band. The three tiers are comprised of three different levels of spectrum access; Incumbent Access, Priority Access and General Authorized Access. In accordance and fulfillment with this dynamic spectrum access framework, we present the inclusion of Priority Access tier into a two-tiered privacy-preserving ESC-based dynamic spectrum access system.
Master of Science

Notre objectif est la conception d'algorithmes d'ordonnancement temps réel en-ligne faisables (i.e., garantissant le respect des contraintes temporelles imposées au systèmes) optimisant 1) l'utilisation de la plate-forme d'exécution (i.e., utiliser au mieux le potentiel de la plate-forme d'exécution tout en garantissant le respect des contraintes temporelles imposées au système) et/ou 2) optimisant des critères de performances
propres à l'application.

Deux cas ont été analysés : le cas de tâches indépendantes périodiques s'exécutant sur un processeur et le cas de flux de messages indépendants périodiques sur un réseau de terrain avec accès au médium priorisé.

Nous avons donc proposé pour traiter les deux problèmatiques abordées :
1) des méthodes de configurations permettant d'optimiser l'utilisation de la plate-forme d'exécution en fixant d'une manière appropriée les paramètres : des politiques ou des activités du système considéré. Deux études ont été conduites dans ce cadre~: l'allocation des ``offsets'' dans les systèmes ``offset free'' et l'allocation de priorités, de politiques et de quantum dans
les systèmes conformes au standard Posix~1003.1b,
2) une nouvelle classe de politiques d'ordonnancement permettant
d'optimiser des critères de performances propres à l'application.

L’objectif que nous nous sommes fixés dans ce travail est la conception d’algorithmes d’ordonnancement temps réel en-ligne faisables optimisant l’utilisation de la plate-forme d’exécution et/ou des critères applicatifs de qualité de service propres à l’application. Nous avons en particulier étudié l’ordonnancement d’activités sur une ressource unique. Deux cas ont été analysés : le cas de tâches indépendantes périodiques s’exécutant sur un processeur et le cas de flux de messages indépendants périodiques sur un réseau de terrain avec accès au médium priorisé. Nos contributions reposent sur le “modèle classique” de l’ordonnancement temps réel où le système est représenté par un ensemble d’activités périodiques indépendantes et deux problématiques ont été abordées : • optimisation de l’utilisation de la plate-forme d’exécution : utiliser au mieux le potentiel de la plate-forme d’exécution tout en garantissant le respect des contraintes temporelles imposées au système ; ceci optimise le nombre de configurations faisables, • optimisation des critères applicatifs de qualité de service propres à l’application (i.e., pris en compte des performances de l’application autre que la faisabilité) : garantir les contraintes de temps tout en optimisant les performances de l’application. Nous avons donc proposé : • des méthodes de configurations permettant d’optimiser l’utilisation de la plate-forme d’exécution (i.e., maximiser faisabilité) en fixant les paramètres des politiques ou des systèmes considérés d’une manière appropriée. Deux études ont été conduites dans ce cadre : • allocation des “offsets” dans les systèmes “offset free”, • allocation de priorités, de politiques et de quantum dans les systèmes conformes au standard Posix 1003.1b, • une nouvelle classe de politiques d’ordonnancement permettant d’optimiser des critères de performances propres à l’application. De plus, une analyse d’ordonnancement générique pour cette classe a été proposée
Our goal is to come up with feasible (i.e., all required time constraints are met) on-line real-time scheduling algorithms. These algorithms have to optimise 1) the utilisation of the execution platform (i.e., meet time constraints and use platform at its fullest potential) and/or 2) optimise the application dependent performance criteria. We study two cases : the case of independent periodic tasks scheduled on a processor and the case of periodic traffic streams scheduled on a priority bus. To deal with these two problems, we propose : • Configuration methods to allow to optmlise the utilisation rate of the execution platform by setting the parameters of the policies or of the activities of the considered system. We perform two studies : the allocation of offsets in "Offset free" systems (I.E., offsets can be chosen off-line) and the priorities, policies and quantum allocations in systems compliant to the standard Posix 1003.1B, • A new class of scheduling policies to allow optimising application performance dependent criteria

The increasing importance of computer leads to develop new manufacturing methods. One of the most important example
&ldquo
unmanned shop floor&rdquo
model aims, the mankind can work in jobs that they can be more efficient and more comfortable. As the base of this model, in Middle East Technical University Computer Integrated Manufacturing Laboratory (METUCIM) &ldquo
Agent Version 1.1&rdquo
system is developed. Windows Distributed Internet Applications (DNA) modeling technique is used for the software development. In the developed system, by using web pages, one can give work orders to the flexible manufacturing cell in METUCIM. The manufacturing capabilities of the cell are limited by the capabilities of CNC Lathe and CNC Milling machine that exist in the system. By the developed agent based dynamic scheduling method, it is prevented to be only an experimental system for the manufacturing cell. The real manufacturing environment is adapted to the cell that it is possible to give unlimited number of work orders. The work orders can be queued and manufactured according to their &ldquo
priorities&rdquo
. By the &ldquo
web-cam&rdquo
application the given work orders can be watched from the web site so the system reliability is increased for the engineer. In the real manufacturing environment it is very frequent that the &ldquo
urgent part&rdquo
is needed to manufacture. In this system it is possible to give &ldquo
urgent orders&rdquo
for these situations.

This term project deals with the problem of scheduling real-time tasks in overload conditions and techniques for lowering power consumption. Each of these parts features mechanisms and reasons for their using. There are also described specific algorithms, that are implemented, in operating system uC/OS-II, and compared in next phase of master's thesis.

Multi-period portfolio optimization (MPO) has gained a lot of interest in modern portfolio theory due to its consideration for inter-temporal trading e effects, especially market impacts and transactions costs, and for its subtle reliability on return predictability. However, because of the heavy computational demand, portfolio policies based on this approach have been sparsely explored. In that regard, a tractable MPO framework proposed by N. Gârleanu & L. H. Pedersen has been investigated. Using the stochastic control framework, the authors provided a closed form expression of the optimal policy. Moreover, they used a specific, yet flexible return predictability model. Excess returns were expressed using a linear factor model, and the predicting factors were modeled as mean reverting processes. Finally, transactions costs and market impacts were incorporated in the problem formulation as a quadratic function. The elaborated methodology considered that the market returns dynamics are governed by fast and slow mean reverting factors, and that the market transactions costs are not necessarily quadratic. By controlling the exposure to the market returns predicting factors, the aim was to uncover the importance of the mean reversion speeds in the performance of the constructed trading strategies, under realistic market costs. Additionally, for the sake of comparison, trading strategies based on a single-period mean variance optimization were considered. The findings suggest an overall superiority in performance for the studied MPO approach even when the market costs are not quadratic. This was accompanied with evidence of better usability of the factors' mean reversion speed, especially fast reverting factors, and robustness in adapting to transactions costs.
Portföljoptimering över era perioder (MPO) har fått stort intresse inom modern portföljteori. Skälet till detta är att MPO tar hänsyn till inter-temporala handelseffekter, särskilt marknadseffekter och transaktionskostnader, plus dess tillförlitlighet på avkastningsförutsägbarhet. På grund av det stora beräkningsbehovet har dock portföljpolitiken baserad på denna metod inte undersökts mycket. I det avseendet, har en underskriven MPO ramverk som föreslagits av N.Gârleanu L. H. Pedersen undersökts. Med hjälp av stokastiska kontrollramen tillhandahöll författarna formuläret för sluten form av den optimala politiken. Dessutom använde de en specifik, men ändå flexibel returförutsägbarhetsmodell. Överskjutande avkastning uttrycktes med hjälp av en linjärfaktormodell och de förutsägande faktorerna modellerades som genomsnittligaåterföringsprocesser. Slutligen inkorporerades transaktionskostnader och marknadseffekter i problemformuleringen som en kvadratisk funktion. Den utarbetade metodiken ansåg att marknadens avkastningsdynamik styrs av snabba och långsammaåterhämtningsfaktorer, och att kostnaderna för marknadstransaktioner inte nödvändigtvis är kvadratiska. Genom att reglera exponeringen mot marknaden återspeglar förutsägande faktorer, var målet att avslöja vikten av de genomsnittliga omkastningshastigheterna i utförandet av de konstruerade handelsstrategierna, under realistiska marknadskostnader. Dessutom, för jämförelses skull, övervägdes handelsstrategier baserade på en enstaka genomsnittlig variansoptimering. Resultaten tyder på en överlägsen överlägsenhet i prestanda för det studerade MPO-tillvägagångssättet, även när marknadsutgifterna inte är kvadratiska. Detta åtföljdes av bevis för bättre användbarhet av faktorernas genomsnittliga återgångshastighet, särskilt snabba återställningsfaktorer och robusthet vid anpassning till transaktionskostnader

Les modèles d'occupation de niche au sein des communautés locales, la variabilité spatiale de la biodiversité le long des gradients environnementaux du stress et des perturbations, et les processus de succession végétale sont plusieurs sujets fondamentaux en écologie. Récemment, l'approche basée sur les traits est apparue comme un moyen prometteur de comprendre les processus structurant les communautés végétales et cette approche a même été proposée comme méthode pour reconstruire l'écologie communautaire en fonction des traits fonctionnels. Par conséquent, lier ces thèmes fondamentaux en utilisant une lentille fonctionnelle devrait nous donner un aperçu de certaines questions fondamentales en écologie et sera l'objectif principal de ma thèse. En général, mon projet de doctorat vise à étudier les structures de l'occupation de l'espace fonctionnel dans les gradients spatio-temporels. Plus précisément, l'objectif du chapitre 2 est (i) d'étudier les modèles d'occupation de la niche fonctionnelle en calculant trois métriques clés de niche (le volume total de niche fonctionnelle , le chevauchement des niches fonctionnelles et le volume de niche fonctionnel moyen) des communautés pauvres en espèces aux communautés riches en espèces et (ii) de déterminer le principal facteur de la structure observée de l'occupation de la niche fonctionnelle dans les communautés végétales du monde entier. Dans le chapitre 3, je vise à prédire et à expliquer la variation de la richesse en espèces selon les gradients de stress et de perturbation, en reliant le modèle d'équilibre dynamique et l'occupation de la niche fonctionnelle en fonction du cadre développé au chapitre 2. L'objectif du chapitre 4 est de tester expérimentalement l’application d'une méthode d'ordination CSR évaluée globalement en fonction de trois traits de feuilles (surface foliaire, teneur en matière sèche des feuilles et surface foliaire spécifique) dans les études locales. Enfin, l'objectif du chapitre 5 est de tester expérimentalement les hypothèses qui concilient les points de vue déterministes et historiquement contingents de la succession végétale, en étudiant la variation des divergences taxonomiques et fonctionnelles entre les communautés selon des gradients de stress et de perturbation. L'étude globale (chapitre 2) est basée sur une collection de 21 jeux de données, couvrant les biomes tropicaux et tempérés, et se compose de 313 communautés végétales représentant différentes formes de croissance. Les études locales (chapitre 3, 4 et 5) sont basées sur le même système expérimental constitué de 24 mésocosmes présentant différents niveaux de stress et de perturbation. L'expérience a commencé en 2009 avec le même mélange de graines de 30 espèces herbacées semées sur les 24 mésocosmes et s'est terminée en 2016. Nous avons permis la colonisation naturelle de graines de la banque commune de graines de sol et de l'environnement pendant la succession de sept ans. Dix traits ont été mesurés sur cinq individus (échantillonnés directement à partir des mésocosmes) par espèce par mésocosme en 2014 (chapitre 3 et 4). Un autre ensemble de traits (16 traits, y compris certains traits qui ne pouvaient pas être mesurés directement dans les mésocosmes), ont été mesurés au niveau de l'espèce (valeurs moyennes des traits) pour les 34 espèces les plus abondantes (certaines espèces disparues dans les mésocosmes) au cours des sept Ans, en les regroupant séparément pour une saison de croissance. Au chapitre 2, nous avons constaté que les communautés étaient plus diverses en termes fonctionnels (une augmentation du volume fonctionnel total) dans les communautés riches en espèces et que les espèces se chevauchaient davantage au sein de la communauté (augmentation du chevauchement fonctionnel), mais ne divisaient pas plus finement l'espace fonctionnel (aucune réduction du volume fonctionnel moyen). En outre, le filtrage de l'habitat est un processus répandu qui conduit à la caractérisation de l'occupation de niche fonctionnelle dans les communautés végétales. Dans le chapitre 3, nous avons trouvé un modèle similaire d'occupation de niche fonctionnelle sur un système expérimental avec une taille spatiale communautaire constante et un effort d'échantillonnage des traits, qui, avec le chapitre 2, nous a fourni une image plus complète et plus solide de l'occupation de niche fonctionnelle dans les communautés végétales. De plus, nous avons réussi à relier le modèle de l'occupation de la niche fonctionnelle et le modèle d'équilibre dynamique et avons constaté que le filtrage concurrentiel était le processus dominant qui détermine le mode d'occupation de la niche fonctionnelle et la richesse des espèces le long du stress et de la perturbation des gradients. Au chapitre 4, nous fournissons un soutien empirique à une méthode d'ordination CSR calibrée globalement en montrant une relation entre l'abondance relative d'espèces en croissance dans les mésocosmes ayant différents niveaux de fertilité du sol et mortalité indépendante de la densité et leur classification CSR. Au chapitre 5, nous avons montré que la succession d'installations au cours de sept ans dans ces mésocosmes était plus déterministe d'un point de vue fonctionnel, mais plus historiquement contingent d'un point de vue taxonomique et que l'importance relative de la contingence historique a diminué à mesure que l'environnement devenait plus stressé ou perturbé. En conclusion, les structures de l'occupation de l'espace fonctionnel dans (le volume fonctionnel total, le chevauchement fonctionnel et le volume fonctionnel moyen, les Chapitre 2 et 3) ou entre les communautés locales (dissimilarité fonctionnelle, chapitre 5) sont déterministes plutôt que neutres (ou contingence historique ). Les espèces tolératrices de stress sont plus avantagées dans les mésocosmes moins fertiles tandis que les espèces rudérales sont plus avantagées dans les mésocosmes avec plus de mortalité indépendante de la densité.
Abstract : The patterns of niche occupancy within local communities, the spatial variability of biodiversity along environmental gradients of stress and disturbance, and the processes of plant succession are several fundamental topics in ecology. Recently, the trait-based approach has emerged as a promising way to understand the processes structuring plant communities and has even been proposed as a method to rebuild community ecology based on functional traits. Therefore, linking these fundamental themes through a functional lens should give us more insight into some basic questions in ecology and will be the main objective of my thesis. Generally, my PhD project is to investigate the structures of functional space occupancy along both spatial and temporal gradients. Specifically, the objective of Chapter 2 is to investigate the patterns of functional niche occupancy by calculating three key niche metrics (the total functional niche volume, the functional niche overlap and the average functional niche volume) from speciespoor communities to species-rich communities and to determine the main driver of the observed pattern of functional niche occupancy across plant communities worldwide. In Chapter 3, I aim to predict and explain the variation of species richness along gradients of stress and disturbance, by linking the dynamic equilibrium model and functional niche occupancy based on the framework developed in Chapter 2. The objective of Chapter 4 is to experimentally test the application of a globally calibrated CSR ordination method based on three leaf traits (leaf area, leaf dry matter content and specific leaf area) in local studies. Finally, the aim of Chapter 5 is to experimentally test the hypotheses reconciling the deterministic and historically contingent views of plant succession, by investigating the variation of taxonomic and functional dissimilarities between communities along gradients of stress and disturbance. The global study (Chapter 2) is based on a collection 21 trait datasets, spanning tropical to temperate biomes, and consisting of 313 plant communities representing different growth forms. The local studies (Chapter 3, 4 and 5) are based on the same experimental system consisting of 24 mesocosms experiencing different levels of stress and disturbance. The experiment started in 2009 with the same seed mixture of 30 herbaceous species broadcast over the 24 mesocosms and ended in 2016. We allowed natural colonization of seeds from the common soil seed bank and from the surroundings during the seven-year succession. Ten traits were measured on five individuals (sampled directly from the mesocosms) per species per mesocosms in 2014 (Chapter 3 and 4). Another set of traits (16 traits including some traits that were not able to measured directly in the mesocosms) were measured at the species level (species mean traits values) for the 34 most abundant species (some species disappeared in the mesocosms) over the seven years, by regrowing them separately for one growing season. In Chapter 2, we found communities were more functionally diverse (an increase in total functional volume) in species-rich communities, and species overlapped more within the community (an increase in functional overlap) but did not more finely divide the functional space (no decline in average functional volume). Moreover, habitat filtering is a widespread process driving the pattern of functional niche occupancy across plant communities. In Chapter 3, we found a similar pattern of functional niche occupancy on an experimental system with a constant community spatial size and trait-sampling effort, which together with Chapter 2 provided us a more comprehensive and robust picture of functional niche occupancy across plant communities. In addition, we succeeded in linking the pattern of functional niche occupancy and the dynamic equilibrium model and found that habitat filtering was the dominant process determining the pattern of functional niche occupancy and species richness along the gradients stress and disturbance. In Chapter 4, we provide empirical support for a globally calibrated CSR ordination method by showing a relationship between the relative abundance of species growing in mesocosms having different levels of soil fertility and density-independent mortality and their CSR classification. In Chapter 5, we showed that plant succession over seven years in these mesocosms was more deterministic from a functional perspective but more historically contingent from a taxonomic perspective, and that the relative importance of historical contingency decreased as the environment became more stressed or disturbed. In conclusion, the structures of functional space occupancy within (the total functional volume, the functional overlap and the average functional volume; Chapter 2 and 3) or between local communities (functional dissimilarity, Chapter 5) are deterministic rather than neutral (or historical contingency). Stress-tolerators were more favored in high stress communities, while ruderals are more favored in high disturbed mesocosms (Chapter 4).

Understanding mechanisms regulating the assembly of ecological communities is a major goal of community ecology. I combined experimental and theoretical approaches to investigate the influences of various ecological factors on the assembly of protist communities. My research included three experimental studies and one theoretical study. Two experimental studies used freshwater heterotrophic ciliated protists as model organisms to examine how species dispersal across local communities and functional and phylogenetic diversity of the species pool influence historical contingency of the assembled communities, respectively. The results of the first experiment showed that the differences in species colonization history led to alternative community states that substantially differed in species composition and abundances, regardless of the level of species dispersal. The results of the second experiment showed that historical contingency, measured by beta diversity and the strength of inhibitive priority effects decreased as phylogenetic and functional diversity of the species pool increased. In the third experimental study, I used the same model system and observed positive relationships between phylogenetic diversity and temporal stability of community biomass. These positive relationships are likely due to the reduced competition among species and increased asynchronous species responses to environmental changes under higher phylogenetic diversity. The theoretical study explored how phytoplankton and zooplankton coevolution drives species diversity patterns along productivity gradients in a mathematical model system. I explored the conditions for evolutionary divergence in phytoplankton and zooplankton and the consequent productivity-diversity relationships (PDR) using the theory of adaptive dynamics and numerical simulations. The results of numerical simulations showed that the coevolutionary dynamics of phytoplankton and zooplankton can generate transient unimodal or positive PDRs, and positive PDRs when the systems reach steady states. The findings of my research suggest an important role of traits and species ecological difference in understanding causes and consequences of biodiversity in community ecology.

Dans cette thèse, nous proposons de construire de meilleurs modèles Processus Gaussiens (GPs) en intégrant les connaissances antérieures avec des données expérimentales. En raison du coût élevé de l’exécution d’expériences sur les systèmes physiques, les modèles numériques deviennent un moyen évident de concevoir des systèmes physiques. Traditionnellement, ces modèles ont été construits expérimentalement et itérativement; une méthode plus rentable de construction de modèles consiste à utiliser des algorithmes d’apprentissage automatique. Nous démontrons comment créer des modèles en intégrant une connaissance antérieure en modifiant les fonctions de covariance. Nous proposons des modèles GP pour différents phénomènes physiques en mécanique des fluides.De même, les lois physiques entre plusieurs sorties peuvent être appliquées en manipulant les fonctions de covariance. Pour chaque application, nous comparons le modèle proposé avec le modèle de l’état de l’art et démontrons les gains de coût ou de performance obtenus
In this thesis, we propose to build better Gaussian Process (GP) modelsby integrating the prior knowledge of Aircraft design with experimental data. Due tothe high cost of performing experiments on physical systems, models become an efficientmeans to designing physical systems. We demonstrate how to create efficient models byincorporating the prior information from engineering design, mainly by changing the covariancefunctions of the GP.We propose GP models to detect onset of non-linearity, detectmodal parameters and interpolate position of shock in aerodynamic experiments. Similarly,physical laws between multiple outputs can be enforced by manipulating the covariancefunctions, we propose to integrate flight-mechanics to better identify loads using thesemodels. For each application we compare the proposed model with the state-of-the-artmodel and demonstrate the cost or performance gains achieved

Des procédures de classement sont largement utilisées pour décrire les phénomènes observés dans de nombreux domaines des sciences sociales et naturelles, par exemple la sociologie, l’économie, la linguistique, la démographie, la physique, la biologie, etc.Dans cette thèse, nous nous sommes attachés à l’étude des propriétés de classement et des dynamiques sous-jacentes intégrées dans les systèmes complexes. En particulier,nous nous sommes concentrés sur les classements par score ou par prix dans les systèmes sportifs et les classements d’utilisation des mots ou caractères dans les langues humaines. Le but est de comprendre les mécanismes sous-jacents à ces questions en utilisant les méthodes de la physique statistique, de la statistique bayésienne et de la modélisation multi-agents. Les résultats concrets concernent les aspects suivants.Nous avons tout d’abord traité une étude sur les classements par score/prix dans les systèmes sportifs et analysé 40 échantillons de données dans 12 disciplines sportives différentes. Nous avons trouvé des similitudes frappantes dans différents sports, à savoir le fait que la répartition des résultats/prix suit les lois puissance universelles.Nous avons également montré que le principe de Pareto est largement respecté dans de nombreux systèmes sociaux: ainsi 20% des joueurs accumulent 80% des scores et de l’argent. Les données concernant les matchs de tennis en individuels nous ont révélé que lorsque deux joueurs s’affrontent, la probabilité que le joueur de rang supérieur gagne est liée à la différence de rang des deux adversaires. Afin de comprendre les origines de la mise à l’échelle universelle, nous avons proposé un modèle multi-agents,qui peut simuler les matchs de joueurs à travers différentes compétitions. Les résultats de nos simulations sont cohérents avec les résultats empiriques. L’extension du domaine d’étude de la simulation indique que le modèle est assez robuste par rapport aux modifications de certains paramètres. La loi de Zipf est le comportement le plus régulièrement observé dans la linguistique statistique. Elle a dès lors servi de prototype pour les relations entre rang d’apparitions et fréquence d’apparitions (relations rang-fréquence dans la suite du texte) et les lois d’échelle dans les sciences naturelles. Nous avons étudié plusieurs textes, précisé le domaine de validité de la loi de Zipf, et trouvé que la plage de validité augmente lors du mélange de différents textes. Basé sur l’analyse sémantique latente, nous avons proposé un modèle probabiliste, dans lequel nous avons supposé que les mots sont ajoutés au texte avec des probabilités aléatoires, tandis que leur densité a priori est liée, via la statistique bayésienne, aux caractéristiques générales du lexique mental de l’auteur de ce même texte. Notre modèle explique la loi de Zipf ainsi que ses limites de validité, et la généralise aux hautes et basses fréquences et au hapax legomena.Dans une autre étude, nous avons précisé les relations rang-fréquence pour les caractères chinois. Nous avons choisi d’étudier des textes courts en premier, car pour le bien de l’analyse rang fréquence, les longs textes ne sont que des mélanges de textes plus courts, thématiquement homogènes. Nos résultats ont montré que la loi de Zipf appliqués aux caractères chinois tient parfaitement pour des textes assez courts (quelques milliers de caractères différents). Le même domaine de validité est observé pour les textes courts anglais. Nous avons soutenu que les longs textes chinois montrent une structure hiérarchique à deux couches: des caractères dont la fréquence d’apparition suit une loi puissance (première couche) et des caractères dont l’apparition suit une loi exponentielle (deuxième couche)
Ranking procedures are widely used to describe the phenomena in many differentfields of social and natural sciences, e.g., sociology, economics, linguistics, demography,physics, biology, etc. In this dissertation, we dedicated to study the ranking propertiesand underlying dynamics embedded in complex systems. In particular, we focused onthe scores/prizes ranking in sports systems and the words/characters usage ranking inhuman languages. The aim is to understand the mechanisms behind these issues byusing the methods of statistical physics, Bayesian statistics and agent-based modeling.The concrete results concern the following aspects.We took up an interesting topic on the scores/prizes ranking in sports systems, andanalyzed 40 data samples in 12 different sports fields. We found the striking similaritiesin different sports, i.e., the distributions of scores/prizes follow the universal powerlaws. We also showed that the data yielded the Pareto principle extensively observedin many social systems: 20% of the players accumulate 80% of the scores and money.For the tennis head-to-head data, we revealed that when two players compete, theprobability that the higher-ranked player will win is related to the rank difference ofthe two opponents. In order to understand the origins of the universal scaling, weproposed an agent-based model, which can simulate the competitions of players indifferent matches, and results from our simulations are consistent with the empiricalfindings. Extensive simulation studies indicate that the model is quite robust withrespect to the modifications of some parameters.Zipf’s law is the major regularity of statistical linguistics that served as a prototypefor the rank-frequency relations and scaling laws in natural sciences. We investigatedseveral English texts, clarified the valid range of Zipf’s law, and found this valid rangeincreases upon mixing different texts. Based on the latent semantic analysis, we proposeda probabilistic model, in which we assumed that the words are drawn into thetext with random probabilities, while their apriori density relates, via Bayesian statistics,to the general features of mental lexicon of the author who produced the text. Ourmodel explained the Zipf’s law together with the limits of its validity, its generalizationto high and low frequencies and hapax legomena. In another work, we specified the rank-frequency relations for Chinese characters. We chose to study the short texts first, since for the sake of the rank-frequency analysis,long texts are just mixtures of shorter, thematically homogenous pieces. Our resultsshowed that the Zipf’s law for Chinese characters perfectly holds for sufficiently shorttexts (few thousand different characters), and the scenario of its validity is similar tothat for short English texts. We argued long Chinese texts display a two-layer, hierarchicstructure: power-law rank-frequency characters (first layer) and the exponentialones (second layer). The previous results on the invalidity of the Zipf’s law for longtexts are accounted for by showing that in between of the Zipfian range and the regionof very rare characters (hapax legomena) there emerges a range of ranks, wherethe rank-frequency relation is approximately exponential. From comparative analysisof rank-frequency relations for Chinese and English, we suggested the characters playfor Chinese writers the same role as the words for those writing within alphabeticalsystems

Modern traffic signal control systems have not changed significantly in the past 40-50 years. The most widely applied traffic signal control systems are still time-of-day, coordinated-actuated system, since many existing advanced adaptive signal control systems are too complicated and fathomless for most of people. Recent advances in communications standards and technologies provide the basis for significant improvements in traffic signal control capabilities. In the United States, the IntelliDriveSM program (originally called Vehicle Infrastructure Integration - VII) has identified 5.9GHz Digital Short Range Communications (DSRC) as the primary communications mode for vehicle-to-vehicle (v2v) and vehicle-to-infrastructure (v2i) safety based applications, denoted as v2x. The ability for vehicles and the infrastructure to communication information is a significant advance over the current system capability of point presence and passage detection that is used in traffic control systems. Given enriched data from IntelliDriveSM, the problem of traffic control can be solved in an innovative data-driven and mathematical way to produce robust and optimal outputs.In this doctoral research, three different problems within a v2x environment- "enhanced pseudo-lane-level vehicle positioning", "robust coordinated-actuated multiple priority control", and "multimodal platoon-based arterial traffic signal control", are addressed with statistical techniques and mathematical programming.First, a pseudo-lane-level GPS positioning system is proposed based on an IntelliDriveSM v2x environment. GPS errors can be categorized into common-mode errors and noncommon-mode errors, where common-mode errors can be mitigated by differential GPS (DGPS) but noncommon-mode cannot. Common-mode GPS errors are cancelled using differential corrections broadcast from the road-side equipment (RSE). With v2i communication, a high fidelity roadway layout map (called MAP in the SAE J2735 standard) and satellite pseudo-range corrections are broadcast by the RSE. To enhance and correct lane level positioning of a vehicle, a statistical process control approach is used to detect significant vehicle driving events such as turning at an intersection or lane-changing. Whenever a turn event is detected, a mathematical program is solved to estimate and update the GPS noncommon-mode errors. Overall the GPS errors are reduced by corrections to both common-mode and noncommon-mode errors.Second, an analytical mathematical model, a mixed-integer linear program (MILP), is developed to provide robust real-time multiple priority control, assuming penetration of IntelliDriveSM is limited to emergency vehicles and transit vehicles. This is believed to be the first mathematical formulation which accommodates advanced features of modern traffic controllers, such as green extension and vehicle actuations, to provide flexibility in implementation of optimal signal plans. Signal coordination between adjacent signals is addressed by virtual coordination requests which behave significantly different than the current coordination control in a coordinated-actuated controller. The proposed new coordination method can handle both priority and coordination together to reduce and balance delays for buses and automobiles with real-time optimized solutions.The robust multiple priority control problem was simplified as a polynomial cut problem with some reasonable assumptions and applied on a real-world intersection at Southern Ave. & 67 Ave. in Phoenix, AZ on February 22, 2010 and March 10, 2010. The roadside equipment (RSE) was installed in the traffic signal control cabinet and connected with a live traffic signal controller via Ethernet. With the support of Maricopa County's Regional Emergency Action Coordinating (REACT) team, three REACT vehicles were equipped with onboard equipments (OBE). Different priority scenarios were tested including concurrent requests, conflicting requests, and mixed requests. The experiments showed that the traffic controller was able to perform desirably under each scenario.Finally, a unified platoon-based mathematical formulation called PAMSCOD is presented to perform online arterial (network) traffic signal control while considering multiple travel modes in the IntelliDriveSM environment with high market penetration, including passenger vehicles. First, a hierarchical platoon recognition algorithm is proposed to identify platoons in real-time. This algorithm can output the number of platoons approaching each intersection. Second, a mixed-integer linear program (MILP) is solved to determine the future optimal signal plans based on the real-time platoon data (and the platoon request for service) and current traffic controller status. Deviating from the traditional common network cycle length, PAMSCOD aims to provide multi-modal dynamical progression (MDP) on the arterial based on the real-time platoon information. The integer feasible solution region is enhanced in order to reduce the solution times by assuming a first-come, first-serve discipline for the platoon requests on the same approach. Microscopic online simulation in VISSIM shows that PAMSCOD can easily handle two traffic modes including buses and automobiles jointly and significantly reduce delays for both modes, compared with SYNCHRO optimized plans.

O banco de sementes de plantas daninhas pode vir a ser um sério problema para a atividade agrícola por manter infestações por longos períodos. A dinâmica da população de plantas daninhas pode ser representada por modelos matemáticos que relaciona as densidades de sementes produzidas e de plântulas em áreas de cultivo. Os valores dos parâmetros dos modelos podem ser inferidos diretamente de experimentação e análise estatística. O presente trabalho tem por objetivo estimar parâmetros de populações das plantas daninhas anuais denominadas Digitaria ciliares, Panicum maximum e Euphorbia heterophylla e avaliar um modelo espacial com 2 e 3 parâmetros, a partir de um experimento conduzido em cultura de Zea mays (milho) usando inferência Bayesiana.
The seeds bank of weed could be a serious problem to the agricultural activity because it maintains infestations for long periods. The dynamics of weed populations can be described by mathematical models that relates the produced seeds and seedlings densities in areas of crop. The values of the parameters of the models can be inferred from experimentation and statistics analysis. The objective of this work is to estimate parameters of anual weed populations denoted Digitaria ciliares, Panicum maximum e Euphorbia heterophylla and evaluate a spatial model with 2 and 3 parameters from experimental data of Zea mays (corn) fields using Bayesian inference.

La quantification du métabolisme musculaire énergétique et de la capacité mitochondriale est d'un intérêt crucial pour étudier les troubles musculaires, les maladies métaboliques ou cardiovasculaires comme la myopathie mitochondriale, le diabète ou les maladies artérielles périphériques. La spectroscopie 31P est un moyen non invasif de monitorer le métabolisme énergétique et les concentrations dynamiques de métabolites phosphorylés pendant ou après un exercice et fournit des informations sur la capacité mitochondriale et oxydative du muscle squelettique. L'évaluation du métabolisme énergétique par spectroscopie 31P peut se faire par spectroscopie non localisée, spectroscopie monovoxel et imagerie spectroscopique par résonance magnétique (MRSI). Dans la pratique clinique, la spectroscopie 31P non localisée est généralement réalisée, ce qui empêche de mesurer les informations métaboliques de différents muscles individuellement, et une information moyenne résultant du muscle entier est collectée en une seule fois par la bobine de surface utilisée pour l'expérience. L'utilisation de la spectroscopie 31P localisée permettrait d'accéder à des informations spatialement résolues et de motiver le développement de nouvelles séquences intégrant les développements techniques les plus avancés. L'imagerie spectroscopique par résonance magnétique (ISRM) disponible dans les systèmes cliniques a un temps d'acquisition très long qui limite son utilisation clinique à l'acquisition statique, alors que ce qui est d’intérêt est essentiellement la capacité à mesurer dynamiquement les variations de concentration des métabolites phosphorylés au cours d’un protocole d'exercice. Les développements méthodologiques sur l’ISRM réalisés dans le cadre de cette thèse, se sont attaqués précisément à réduire le temps d'acquisition, en vue d’applications cliniques. Une méthode d'acquisition ISRM rapide a donc été développée, impliquant un échantillonnage non cartésien dans l'espace k (échantillonnage en spirale), couplé à un sous-échantillonnage intelligent de la dimension temporelle, exploitant la connaissance a priori de la parcimonie du support spectral et une estimation par moindres carrés pour la reconstruction du signal. Cette méthode a été validée à l'aide de simulations et mise en œuvre dans un système IRM, optimisée puis testée in vivo sur le muscle du mollet pour des applications ISRM 1H et 31P. Des applications dynamiques 31P ont également été réalisées à 3T et l'utilisation de la séquence sous-échantillonnée CSI spiral développée a montré qu'elle était capable de révéler les changements dynamiques attendus dans le PCr. La quantification du signal nous a permis en outre d'accéder à la capacité mitochondriale, avec une résolution temporelle dynamique deux fois supérieure à celle du cas ISRM spiral avec échantillonnage régulier, et une résolution temporelle similaire à celle de l’ISRM non localisée utilisée conventionnellement. Ces développements sont d'un intérêt crucial pour une évaluation spatialement résolue de la capacité mitochondriale au sein de différents muscles ; c'est-à-dire pour mettre en évidence des altérations musculaires individuelles liées à des dommages spécifiques ou des différences de consommation d'énergie entre les différents chefs musculaires pendant l'exercice. Des améliorations de séquence sur la spectroscopie 31P localisée 1D ont également été intégrées dans un protocole clinique en cours, afin, à terme, d’appliquer les développements de séquence réalisés pendant cette thèse à un contexte clinique. D'abord testé sur des volontaires sains pour la reproductibilité, le protocole implique des patients qui souffrent d'artériopathie de la jambe inférieure. L'objectif était d'évaluer la capacité mitochondriale de ces patients avant et après une revascularisation de l'artère endommagée. Les résultats ont montré une amélioration significative de la capacité mitochondriale après revascularisation
Quantifying energetic muscular metabolism and mitochondrial capacity are of crucial interest to reveal muscular disorders, metabolic diseases or cardiovascular diseases like mitochondrial myopathy, diabetes or peripheral arthery diseases. 31P spectroscopy is a non-invasive way to monitor energetic metabolism and dynamic concentrations of 31P during exercise or after during recovery, and provides informations on mitochondrial and oxidative capacity. The assessment of energetic metabolism via 31P spectroscopy can be done with non-localized spectroscopy, single voxel selection spectroscopy and Magnetic Resonance Spectroscopic Imaging (MRSI). In clinical practice, mostly non localized 31P spectroscopy is done, preventing metabolic information from different individual muscles to be measured, but an average information resulting from the whole muscle and collected at once by the surface coil used for the experiment. The use of localized 31P spectroscopy would enable to access spatially resolved information and motivate the development of new home made sequences integrating the most advanced technical developments. Magnetic resonance Chemical shift Spectroscopic Imaging (CSI) available in clinical systems have very long acquisition time that limits their clinical use to static acquisition, while this is essentially the capacity to measure 31P dynamically during an exercise protocol that is of interest. The methodological developments on MRSI realized In the context of this thesis, aimed precisely at reducing the acquisition time and in view of some clinical applications. A fast MRSI acquisition method has thus been developed involving a non-Cartesian k-space Sampling (spiral sampling), coupled to a smart under-sampling of the temporal dimension, exploiting a priori known spectral support and a least-square estimation for signal reconstruction. This method has been validated using simulations, and implemented in a MR scanner, optimized and then tested in vivo on the calf muscle for 1H and 31P MRSI applications. Dynamic 31P applications were also performed at 3T and the use of the under-sampled CSI_spiral MRSI developed sequence has been shown to adequately reveal the expected dynamic changes in PCr. Quantification of the signal further enable us to access mitochondrial capacity, with a twice higher dynamic temporal resolution compared to the fully sampled CSI_spiral MRSI case, and similar temporal resolution as the non-localized classically used MRS sequence. Those developments are of crucial interest for a spatially resolved assessment of mitochondrial capacity within different muscles, i.e. to point out individual muscle alterations related to specific damages or differences between muscle energy consumption during the exercise. Sequence improvements on 1D localized 31P spectroscopy were also integrated in the clinical sequence and used in an on-going clinical protocol; in order, in the long term, to apply the sequence developments carried out during this thesis to a clinical context. First tested on safe volunteers for reproducibility, the protocol involves patients that suffer from lower leg arteriopathy. The objective was to assess mitochondrial capacity of those patients before and after a revascularization of the damaged artery. Results showed significant improvement in mitochondrial capacity after revascularization

Transit Signal Priority (TSP) is a popular Traffic Demand Management strategy used to enhance the performance of transit systems by modifying the signal control logic to give transit signal priority through signalized intersections. Conventional TSP strategies used in most cities have been shown to offer significant benefits in minimizing the delays of transit vehicles. However, there have been several concerns about the shortcomings of conventional TSP strategies which limited their applications. The main concern is the potential negative impact on the cross street traffic. Another concern is the static nature of conventional TSP strategies and the lack of responsiveness to real-time traffic and transit conditions. This thesis describes the development and evaluation of a dynamic Transit Signal Priority (TSP) control system which has the ability to provide signal priority in response to real-time traffic and transit conditions. The dynamic TSP system consists of three main components: a virtual detection system, a dynamic arrival prediction model, and a dynamic TSP algorithm. The methodology followed to develop the system consisted of three main steps. The first was to develop a microsimulation model that would be used to test and evaluate the performance of the dynamic TSP system. In the model, Automatic Vehicle location (AVL) was used as the virtual detection system. The second step was the development of several bus arrival prediction models using linear regression and neuro-fuzzy methods. Techniques such as Kalman and Bayes filters were used to refine the prediction. The last step was the development of a dynamic TSP algorithm that would decide what TSP strategy to use and when to apply it. The dynamic TSP system was tested and compared to the conventional TSP system using the microsimulation model. Scenarios with varying simulation parameters and traffic volumes were tested. Results showed that when an accurate prediction model was used, the dynamic TSP system outperformed the conventional one. The dynamic TSP system could be further enhanced if better arrival prediction models are used, more TSP strategies are evaluated, and a larger scale of implementation is studied.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

碩士
國立中正大學
資訊工程所
94
In a multi-tasking computer system with hard disks as the main storage system, processes issue disk I/O requests to the operating system before accessing files. Because the speed of disk I/O operations is much slower than the speed of processor operations, I/O management often plays an important role on system performance, especially when the system has to deal with a lot of I/O requests. In order to facilitate system management, prioritized process scheduling mechanisms have been widely applied for CPU resource scheduling. However, as I/O management is usually done by scheduling on I/O requests or I/O devices, it is difficult to manage priorities of I/O requests and schedule I/O requests by processes respectively. This paper proposes an I/O scheduling mechanism in order to manage I/O priorities by processes so that the response time of processes can be reduced at users' will. We design a dynamic priority scheduling mechanism for operating systems to manage I/O behavior of processes by scheduling I/O requests. Furthermore, we provide a friendly user interface to configure I/O management at run-time according to the behavior of individual processes.

In this thesis, we first study delay systems with different classes of impatient customers. We analyze the M/GI/1+M queue serving two priority classes under the static non-preemptive priority discipline. We also study the multi-server priority queue considering two cases depending on the time-to-abandon distribution being exponentially distributed or deterministic. In all models, we obtain the Laplace transforms of the virtual waiting time for each class by exploiting the level-crossing method. This enables us to obtain the steady-state system performance measures. In the second part, we consider the steady-state waiting time distributions of a two class M/GI/1 queue operating under a dynamic priority discipline. We find an accurate approximation for the steady-state waiting time distribution of the low-priority customers which allows us to study how they are penalized as the priority parameter increases. We also obtain bounds for the variance of the waiting time of high-priority customers.

碩士
國立臺灣大學
資訊工程學研究所
96
In hard-real-time environment, scheduling periodic tasks upon multiprocessors is one of the most popular problems where uniform multiprocessor scheduling is a well-known one. In uniform multiprocessor scheduling, execution time of each task in one processor is proportional to the computing capacity of this processor. From previous works, there are only approximate feasible solutions for on-line scheduling on uniform multiprocessors. In this thesis, with task migration, we first present a novel model called T-Ler plane for uniform multiprocessors to describe the behavior of tasks and processors, and two optimal algorithms based on T-Ler plane to schedule dynamic-priority real-time tasks on uniform multiprocessors. To make it practical and reduce context switches, we also present a polynomial-time algorithm to bound the times of rescheduling or task migration in a T-Ler plane and give an experimental evaluation for it. Since task migration is easier in SOC multicore processors, our result might be applicable and adapted to many asymmetric multicore platforms.

碩士
國立交通大學
電機資訊學院碩士在職專班
92
MPLS (Multi-Protocol Label Switching) technique not only reserves the high connectivity of traditional IP network, but speeds up IP packet forwarding in a router. Especially, its powerful capability of traffic engineering improves the network resource utilization and Quality of Service. The main key point of this thesis is to use the CR-LDP (Constraint-Based Routed Label Distribution Protocol) technique of MPLS to search for an algorithm, which can fairly distribute resource for a traffic flow according to its priority ,and makes use of the network resource more efficiently . In the DLBP (Dynamic Load Balance Algorithm with Priority) mechanism we propose, when Ingress LSR receives a new traffic flow, it will select a route whose length is the shortest and Free-capacity is larger than or equal to the bandwidth request of the new traffic flow ,and then along the selected route to create an LSP in the MPLS network for the traffic flow . If the Ingress LSR fails to find such a route ,in our mechanism ,it will do its best to reroute some existing smaller traffic flows to another appropriate routes so as to reserve a high capacity route for the new traffic flow. Once the Ingress LSR still fails to find a sufficient bandwidth for the new traffic flow ,we allow the new traffic flow to preempt the reserved bandwidth of another one with lower priority. When selecting which one will be preempted, we need to consider how it can make the use of network resource and the transportation quality optimized. Our results of simulation prove that DLBP indeed makes network resource used effectively and the transportation quality optimized.

碩士
朝陽科技大學
資訊管理系碩士班
95
Multimedia applications in mobile wireless networks require higher Quality of service (QoS) than other kinds of transmission. Thus system should provide different QoS for different priority connection. Seamless handoff is one of the important QoS factors in mobile network. Traditional multi-Guard channel scheme that reserve some bandwidth for handoff call are not adaptive to traffic load changes and cause low system bandwidth utilization problem. This research proposes a fair and efficient bandwidth reservation scheme called Fair_Dynamic Guard Channel (F_DGC), which adapts to various traffic load changes and keeping the handoff blocking rate less than a predefined threshold. Experimental result shows that our method overcomes the drawback of Multi-GC and DGC. This paper divides all connections into four priorities for the system which can be compatible to the backbone network with DiffServ architecture.

碩士
國立交通大學
電信工程系所
95
To efficiently utilize the system resource and satisfy the QoS requirements in current multimedia transmission environment, we propose a dynamic priority-based resource allocation (DPRA) algorithm for IEEE 802.16 uplink system in this thesis. The goal of DPRA algorithm is to maximize system throughput while satisfying diverse QoS requirements. Four types of multimedia traffic defined in IEEE 802.16 are considered, including unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), and best effort (BE) service. These multimedia services are given urgency degrees via dynamic priority values, which will be calculated at the beginning of each frame. The radio resource will be allocated to users according to priority values. Also the DPRA algorithm performs consistent allocation in aspects of subchannel, modulation order, and power. Simulation results show that the proposed DPRA algorithm outperforms the conventional algorithm in terms of system throughput and satisfaction of various QoS requirements. Besides, the proposed DPRA algorithm is also designed to have lower cost of transmission overhead and complexity.

碩士
中原大學
工業工程研究所
89
This research proposes and evaluates several priority assignment heuristics for lots in wafer fabs. Lots are grouped into five classes: super hot, hot, rush, normal, and slow. The priority of each lot can be statically or dynamically determined. Static priority setting means the lot’s priority is determined when it is released, and this priority will not change during the lot’s entire process. Dynamic priority setting means the lot’s priority is dynamically changed based on its slack. Machines are classified into bottleneck and non-bottleneck, based on their average utilization over the past 12, 24, and 72 hours in different experiments. A bottleneck machine uses HPF heuristic to select a lot with the highest priority, while a non-bottleneck machine uses FGCA+ heuristic to select a lot with the least number of steps toward a bottleneck machine. AutoSched simulation models are built to evaluate the performance of the proposed heuristics, including average cycle time, average work-in-process, percent on-time delivery, turn ratio, and progress of processing time. A foundry fab with 346 machines and five major product types with an average of 280 steps is studied. Simulation results show that dynamic priority setting based on 12-hour bottleneck machine identification leads to best performance.

碩士
國立臺灣科技大學
電子工程系
97
In 802.16 system，traffic have two type，one is real time traffic another is non-real time traffic。In most existing packet schedulers giver higher priority to the real time traffic over non-real time traffic unconditionally。If we send real time traffic for long time, and it will caused non-real time traffic serious delay . In order to solve the traffic delay and we proposed a new solved method. In this paper, the SS reports the length of queue in its buffer. The 802.16BS will estimate its length in the period of next frame. If it is almost full, its assigned bandwidth is decreased and the excess bandwidth will be assigned to non-real time traffic. If it is almost empty, more bandwidth will be assigned. This will be completed by assign more or less high priority packets to the real time traffic.

碩士
國立中山大學
電機工程學系研究所
88
Differentiated-Service networks is designed for solving scalability problems through traffic aggregation. However, it can't guarantee end-to-end QoS of individual flow. In this thesis, we propose a Self-Adaptive Control Scheme for Differentiated-Service networks that can improve the throughput of individual flows dynamically. In this scheme, egress routers monitor the average throughput of individual flow, and send the Self-Adaptive Control Messages to ingress routers if need. The ingress router re-allocate network resources to improve throughput of high-priority flows depending on the Control Messages. We use NS-2 simulator to prove that our scheme that can improve throughput of high-priority flows dynamically, and suggest that a better time interval of Self-Adaptive control can be determined based on the queue sizes, packets arrival rate and departure rate. Finally, we use Random Early Detection (RED) queue instead of Drop-Tail queue to reduce unfairness of individual flows when there are congestion and insufficient network resources.

碩士
國立臺灣科技大學
電子工程系
95
The scalable extension of H.264/AVC, called H.264/SVC, is a current standardization project of Joint Video Team (JVT). An encoded SVC bitstream consists of an H.264/AVC-compatible base layer and one or more scalable enhance layers. In order to meet requirements of various clients, some scalable enhance layers can be truncated. This thesis focuses on the investigation of H.264/SVC transmission over IEEE 802.11e through a Cross-layer Architecture. The Cross-layer Architecture, which interacts Network Abstraction Layer and Dynamic Priority Adjustment Mechanism based on IEEE 802.11e MAC layer, provides differentiated services according to the importance of scalable video packets. The simulations are conducted with Qualnet 4.0. The simulation results show that our approach provides better video quality.

Thesis (M.S.)--University of Wisconsin--Madison, 1992.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 33).

碩士
國立臺灣科技大學
資訊工程系
92
In the past, most research for channel allocation focused on the reduction of forced-termination probability for handoff voice calls and sacrificed the blocking probability of new voice calls and dropping probability of data. This design seems to be inelastic and fails to work for different traffic load. We thus in this thesis propose a more elastic scheme called dynamic priority with triple queue (DPTQ), which offers better priority-based allocation between handoff voice calls and new voice calls using information of relative queue lengths. Besides, we use a channel reallocation scheme to reduce the dropping probability of data. Dividing channels in each cell into common channels and priority channels only for handoff voice calls and new voice calls, we mathematically analyze DPTQ using the technique of Markov chains. Accompanying with simulations, we show that DPTQ possesses better flexibility and performance compared to dual-threshold with triple queue (DTTQ) which is a variant of dual-threshold bandwidth reservation (DTBR).

碩士
國立高雄應用科技大學
電子工程系
99
ZigBee[1][2] is a new communication network technology , its agreement standard is based on IEEE802.15.4 [3] network. And has a low data rate, low cost, low power consumption characteristics, and therefore widely used in wireless sensor networks, short-range process control, home control and industrial automation. This paper studies the practical application of Zigbee encounter -ed the problems and proposed solutions. One, based on the complex environment produced by the network orphan, this paper will simulate this environment to describe the phenomenon. Second, automatic network topology configuration problem, for larger networks, the network topology will increase the difficulties of planning and management, and may also increase the network installation costs. Third, the network node layout and testing issues. This paper focused on three questions for study and discussion, and to propose a dynamic priority of the network topology management method to solve the above problem, this method combines the existing Zigbee automatic network topology configuration and the technology of the dynamic priority to adjust the network topology in this paper. Finally, by the technology of network management to enhance the Zigbee network to operate in the complex environment of stability and reduce the complexity of topology management and network installion and maintenance costs purposes.

碩士
國立臺灣科技大學
電機工程系
106
Abstract The development of the Internet of Things (IoT) has received increasing attention and gradually changes people's living habits. In the future, there will be more devices connected to the Internet. Wireless sensor network (WSN) is consisted of several sensor devices and transmits data through wireless transmission. It is characterized by its short distance transmission, low cost, low power consumption, low bandwidth requirements, and has a small device size. It can be applied in different fields such as: agriculture, telemedicine care, smart grid, environmental monitoring and industrial automation etc. The IEEE 802.15.4 standard is a specification for wireless sensing networks. The standard provides superframe structure to transmit data. It is divided into active period and inactive period, and the length is determined by superframe order and beacon order. However, these two parameters cannot be adjusted by considering the network traffic load, which may reduce the throughput, increase power consumption or add a delay. In the standard, the device uses the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism to transmit data during the contention access period. Nevertheless, the transmission parameters of this mechanism are the same for all frames and cannot meet the transmission requirements of different priority frames. In the contention free period, the device does not have to compete with other devices for transmission channels. Instead, it is assigned to a specific time to do, known as guaranteed time slots (GTSs). It can provide for the transmission of real-time data, yet not consider the size of the data assignment may cause the problem of bandwidth waste. At present, there are many methods to improve the standard and provide different wireless sensor network applications to meet the requirements. But these methods only focus on one or two issues for quality of service (QoS), and with few considerations on multiple requirements. Therefore, this thesis proposes a priority based scheme to dynamic superframe adjustment with guaranteed time slot(PDSGTS). Simulation results show that compared with the IEEE 802.15.4 standard, the PDSGTS mechanism can effectively increase the goodput and reduce the transmission delay. Keywords: IEEE 802.15.4, wireless sensor network, Superframe adjust, CSMA/CA

碩士
國立交通大學
電信工程研究所
106
In this thesis, we propose an AI-driven priority-based scheduling algorithm for wireless medical networks with the selfish and unselfish gateways. Unlike most of existing works, we focus on beyond wireless body area network (beyond-WBAN) communications between gateways and the base station. We propose an intelligent priority-based packet scheduling algorithm. For the expectation-based detection scheme, we derive analytic results that are consistent with simulation results. In addition, we proposed a novel AI-based scheme for the BS to detect the selfish misbehavior of the gateway. Simulation results show that the proposed AI-based approach outperforms the expectation-based approach. Furthermore, we use simulation results to show that the proposed priority-based scheme is superior to the non-priority scheme in terms of providing differentiated quality-of-services to users.

碩士
國立成功大學
電腦與通信工程研究所
104
As the evolvement of network and cloud computing, network system plays an important role in information transferring. Current network architecture has no longer satisfied the flexibility and adaptability which applications need. Software-Defined Networking (SDN), proposed recently, is recognized to be a feasible solution. The crucial concept of Software-Defined Networking is to decouple the data plane and the control plane, and making control plane programmable. The control plane controls transferring devices in data plane. Since controllers have global visibility of network and the ability to adjust current network status, network management technology like flow control and quality guarantee schemes are able to be adopted to make better network resources allocation. Based on above mentioned, the research proposed a dynamic flow-path migration mechanism with priority division in Software-Defined Networking. In the mechanism, the required bandwidth of high priority flows are considered, and guaranteed as much as possible by dynamically migrating flow-paths when needing of requests are unsatisfied. The migration method considers remain bandwidth and number of flows on path, and avoids duplicate flow assignment on single link. The result shows that the dynamic flow-path migration mechanism implemented in OpenFlow environment not only guarantees the required bandwidth of high priority flows, but to some degree avoids interfering normal flows transmissions.

ABSTRACT Now a days, Mobile computing networks revolutionize the way computers are used. Mobile hosts have small memory, a relatively slow processor and low power batteries, and communicate over low bandwidth wireless communication links. Distributed dynamic channel allocation in mobile cellular networks and other similar structures is a fundamental resource management problem. It has aroma of distributed mutual exclusion but is not exactly mutual exclusion problem because a channel must be reused in different cells. Existing mutual exclusion algorithms for cellular systems are not suitable to mobile systems due to above limitations. Here, the exact relation being established between the both algorithms. Specifically, we describe the procedure of relaxed mutual exclusion to modularize the problem of distributed channel allocation. A geographical area is divided into hexagonal cells, every cell uses the same bandwidth, which is divided into channels. Cell phone must use one channel to make a call. Cells have different traffic usage of channels such that every cell could need different quantity of channels. Allocation algorithm should dynamically allocate channels (resources) to cells, to get the most efficient usage of available bandwidth using relaxed mutual exclusion. We propose a general algorithm that guarantees relaxed mutual exclusion for a single resource, prove a necessary and sufficient condition for the information structure, and address the issues that arise in relaxed mutual exclusion, including deadlock resolution, dealing with multiple resources, and design of efficient information structure. Here, improvement based on mutual exclusion solution, such as deadlock minimization and broken cells serving extended to multiple channel case is described to an extent to use the bandwidth efficiently. Keywords : Relaxed Mutual Exclusion, channel allocation, deadlock minimization, broken cell serving, TSDP(Two-Step Dynamic-Priority), borrowing scheme

With multiprocessors and multicore processors becoming ubiquitous, focus has shifted from research on uniprocessors to that on multiprocessors. Results derived for the uniprocessor case unfortunately do not always directly extend to the multiprocessor case in a straightforward manner. This necessitates a paradigm shift in the approach used to design and analyse the behaviour of such processors. In the case of Real-time systems, that is, systems characterised by explicit timing constraints, analysis and performance guarantees are more important, as failure is unacceptable. Scheduling algorithms used in Real-time systems have to be carefully designed as the performance of the system depends critically on them. Efficient tests for determining if a set of tasks can be feasibly scheduled on such a computing system using a particular scheduling algorithm thus assumes importance. Traditionally, the ‘task utilization’ parameter has been used for devising such tests. Utilization based tests for Earliest Deadline First(EDF) and Rate Monotonic(RM) scheduling algorithms are known and are well understood for uniprocessor systems. In our work, we derive limits on similar bounds for the multiprocessor case. Our work diners from previous literature in that we explore the case when the individual processors constituting the multiprocessor need not be identical. Each processor in such a system is characterised by a capacity, or speed, and the time taken by a task to execute on a processor is inversely proportional to its speed. Such instances may arise during system upgradation, when faster processors may be added to the system, making it a non-identical multiprocessor, or during processor design, when the different cores on the chip may have different processing power to handle dynamic workloads. We derive results for the partitioned paradigm of multiprocessor scheduling, that is, when tasks are partitioned among the processors, and interprocessor migration after a part of execution is completed is not allowed. Results are derived for both fixed priority algorithms(RM)and dynamic priority algorithms (EDF) used on individual processors. A maximum and minimum limit on the bounds for a ‘greedy’ class of algorithms are established, since the actual value of the bound depends on the algorithm that allocates the tasks. We also derive the utilization bound of an algorithm whose bound is close to the upper limit in both cases. We find that an expression for the utilization bound can be obtained when EDF is used as the uniprocessor scheduling algorithm, but when RM is the uniprocessor scheduling algorithm,an O(mn) algorithm is required to find the utilization bound, where m is the number of tasks in the system and n is the number of processors. Knowledge of such bounds allows us to carry out very fast schedulability tests, although we have the limitation that the tests are sufficient but not necessary to ensure schedulability. We also compare the value of the bounds with those achievable in ‘equivalent’ identical multiprocessor systems and find that the performance guarantees provided by the non-identical multiprocessor system are far higher than those offered by the equivalent identical system.

With multiprocessors and multicore processors becoming ubiquitous, focus has shifted from research on uniprocessors to that on multiprocessors. Results derived for the uniprocessor case unfortunately do not always directly extend to the multiprocessor case in a straightforward manner. This necessitates a paradigm shift in the approach used to design and analyse the behaviour of such processors. In the case of Real-time systems, that is, systems characterised by explicit timing constraints, analysis and performance guarantees are more important, as failure is unacceptable. Scheduling algorithms used in Real-time systems have to be carefully designed as the performance of the system depends critically on them. Efficient tests for determining if a set of tasks can be feasibly scheduled on such a computing system using a particular scheduling algorithm thus assumes importance. Traditionally, the ‘task utilization’ parameter has been used for devising such tests. Utilization based tests for Earliest Deadline First(EDF) and Rate Monotonic(RM) scheduling algorithms are known and are well understood for uniprocessor systems. In our work, we derive limits on similar bounds for the multiprocessor case. Our work diners from previous literature in that we explore the case when the individual processors constituting the multiprocessor need not be identical. Each processor in such a system is characterised by a capacity, or speed, and the time taken by a task to execute on a processor is inversely proportional to its speed. Such instances may arise during system upgradation, when faster processors may be added to the system, making it a non-identical multiprocessor, or during processor design, when the different cores on the chip may have different processing power to handle dynamic workloads. We derive results for the partitioned paradigm of multiprocessor scheduling, that is, when tasks are partitioned among the processors, and interprocessor migration after a part of execution is completed is not allowed. Results are derived for both fixed priority algorithms(RM)and dynamic priority algorithms (EDF) used on individual processors. A maximum and minimum limit on the bounds for a ‘greedy’ class of algorithms are established, since the actual value of the bound depends on the algorithm that allocates the tasks. We also derive the utilization bound of an algorithm whose bound is close to the upper limit in both cases. We find that an expression for the utilization bound can be obtained when EDF is used as the uniprocessor scheduling algorithm, but when RM is the uniprocessor scheduling algorithm,an O(mn) algorithm is required to find the utilization bound, where m is the number of tasks in the system and n is the number of processors. Knowledge of such bounds allows us to carry out very fast schedulability tests, although we have the limitation that the tests are sufficient but not necessary to ensure schedulability. We also compare the value of the bounds with those achievable in ‘equivalent’ identical multiprocessor systems and find that the performance guarantees provided by the non-identical multiprocessor system are far higher than those offered by the equivalent identical system.