Trabalho de investigação desenvolvido na Universidade de Tecnologia e Economia de Budapeste / Tese de mestrado. Mestrado Integrado em Engenharia Civil - Especialização em Estruturas. Faculdade de Engenharia. Universidade do Porto. 2012

Tese de mestrado. Mestrado integrado em Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 2012

La reconfiguration dynamique d'un logiciel peut être un auxiliaire utile pour adapter et maintenir des systèmes informatiques. Dans la plupart des approches, le système doit être interrompu pour que la reconfiguration puisse être exécutée. Cette interruption ne peut convenir aux systèmes temps-réel : il est nécessaires que les contraintes temporelles soient respectées, même lorsque le système est en train d'être reconfiguré.<br />Notre approche se base sur OSA+, un middleware temps-réel. Notre objectif principal est d'être capable de reconfigurer un (ou plusieurs) service lorsque le système est en fonction, avec un temps de non-réponse prévisible et prédéfini, c'est-à-dire un temps pendant lequel le système ne réagit pas à cause de la reconfiguration.<br />Trois approches différentes concernant le blocage ou le non-blocage d'un service sont présentées. Ces approches peuvent être utilisées pour réaliser un compromis entre le temps de reconfiguration et le temps de non-réponse.

The selective infrared (IR) excitation of molecular vibrations is a powerful tool to control the photoreactivity prior to electronic excitation in the ultraviolet / visible (UV/Vis) light regime ("vibrationally mediated chemistry"). For adsorbates on surfaces it has been theoretically predicted that IR preexcitation will lead to higher UV/Vis photodesorption yields and larger cross sections for other photoreactions. In a recent experiment, IR-mediated desorption of molecular hydrogen from a Si(111) surface on which atomic hydrogen and deuterium were co-adsorbed was achieved, following a vibrational mechanism as indicated by the isotope-selectivity. In the present work, selective vibrational IR excitation of adsorbate molecules, treated as multi-dimensional oscillators on dissipative surfaces, has been simulated within the framework of open-system density matrix theory. Not only potential-mediated, inter-mode coupling poses an obstacle to selective excitation but also the coupling of the adsorbate ("system") modes to the electronic and phononic degrees of freedom of the surface ("bath") does. Vibrational relaxation thereby takes place, depending on the availabilty of energetically fitting electron-hole (e/h) pairs and/or phonons (lattice vibrations) in the surface, on time-scales ranging from milliseconds to several hundreds of femtoseconds. On metal surfaces, where the relaxation process of the adsorbate via the e/h pair mechanism dominates, vibrational lifetimes are usually shorter than on insulator or semiconductor surfaces, in the range of picoseconds, being also the timescale of the IR pulses used here. Further inhibiting factors for selectivity can be the harmonicity of a mode and weak dipole activities ("dark modes") rendering vibrational excitation with moderate field intensities difficult. In addition to simple analytical pulses, optimal control theory (OCT) has been employed here to generate a suitable electric field to populate the target state/mode maximally. The complex OCT fields were analyzed by Husimi transformation, resolving the control field in time and energy. The adsorbate/surface systems investigated were CO/Cu(100), H/Si(100) and 2H/Ru(0001). These systems proved to be suitable models to study the above mentioned effects. Further, effects of temperature, pure dephasing (elastic scattering processes), pulse duration and dimensionality (up to four degrees of freedom) were studied. It was possible to selectively excite single vibrational modes, often even state-selective. Special processes like hot-band excitation, vibrationally mediated desorption and the excitation of "dark modes" were simulated. Finally, a novel OCT algorithm in density matrix representation has been developed which allows for time-dependent target operators and thus enables to control the excitation mechanism instead of only the final state. The algorithm is based on a combination of global (iterative) and local (non-iterative) OCT schemes, such that short, globally controlled time-intervals are coupled locally in time. Its numerical performance and accuracy were tested and verified and it was successfully applied to stabilize a two-state linear-combination and to enforce a successive "ladder climbing" in a rather harmonic system, where monochromatic, analytical pulses simultaneously excited several states, leading to a population loss in the target state. / Die selektive Anregung von Molekülschwingungen mittels Infrarotlicht (IR) ist vorteilhaft, um die Wirkungsquerschnitte nachfolgender photochemischer oder photophysikalischer Prozesse zu steigern, welche durch Elektronenanregung mittels ultraviolettem (UV) bzw. sichtbarem (Vis) Licht ausgelöst werden. Für Adsorbatmoleküle auf Oberflächen wurden theoretische Vorhersagen getroffen, dass eine kombinierte (IR plus UV)-Strategie ("schwingungsvermittelte Chemie") die Ausbeute bei Photodesorption und anderen Photoreaktionen deutlich zu erhöhen vermag. Kürzlich wurde im Experiment gezeigt, dass eine rein IR-vermittelte Desorption möglich ist, welche über einen schwingungsangeregten Mechanismus erfolgt. Hierbei wurde molekularer Wasserstoff von einer Si(111)-Oberfläche desorbiert, an der atomarer Wasserstoff und atomares Deuterium gebunden waren. Eine thermische Anregung, die zum Bindungsbruch führt, konnte hierbei wegen der Isotopenselektivität ausgeschlossen werden. In der vorliegenden Arbeit wurde die selektive IR-Schwingungsanregung von Adsorbaten, die als multidimensionale Oszillatoren auf dissipativen Oberflächen behandelt wurden, mit Hilfe der Dichtematrixtheorie für offene Systeme simuliert. Nicht nur die potentialvermittelte Kopplung zwischen den einzelnen Moden ist ein Hindernis für selektive Anregung, sondern auch die Kopplung der Moden des Adsorbats ("Systems") an elektronische und phononische Freiheitsgrade des Substrats ("Bades"). Die Schwingungsrelaxation verläuft hierbei auf Zeitskalen, die von Millisekunden bis hin zu wenigen hundert Femtosekunden reichen, je nach Verfügbarkeit energetisch geeigneter Elektron-Loch-Paar-Anregungen bzw. Phononen (Gitterschwingungen) in der Oberfläche. Auf Metalloberflächen, bei denen die Schwingungrelaxation des Adsorbats zumeist von einem Elektronen-Loch-Paar-Mechanismus dominiert wird, sind die Schwingungslebensdauern normalerweise kürzer als auf Isolator- oder Halbleiteroberflächen und betragen einige Picosekunden, ebenso wie die Zeitskala der hier gewählten IR-Pulse. Weitere Faktoren, die die selektive Anregung behindern können sind die Harmonizität einer Mode und die geringe Dipolaktivität sogenannter "dunkler Moden", die eine Anregung mit moderat intensiven Feldern erschweren. Zusätzlich zu einfachen analytischen Pulsen wurden Felder mittels Optimaler Kontrolltheorie (OCT) erzeugt, um eine(n) Zielzustand/-mode maximal zu populieren. Komplexe OCT Pulse wurden mit Hilfe der Husimi-Transformation analysiert, welche das Kontrollfeld im Zeit- und Energieraum aufzulösen vermag. Die in dieser Arbeit untersuchten Adsorbat/Oberflächen-Systeme waren CO/Cu(100), H/Si(100) und 2H/Ru(0001), die sich als passende Modelle erwiesen, um oben genannte Faktoren zu untersuchen. Desweiteren wurden die Auswirkungen von Temperatur, reiner Dephasierung (elastische Streuprozesse), Dauer des IR-Pulses und Systemdimensionalit"at (Behandlung von bis zu vier Freiheitsgraden) studiert. Einzelne Schwingungsmoden konnten angeregt werden, in vielen Fällen sogar zustandsselektiv. Spezielle Prozesse wie die Anregung "heißer Banden", Desorption via alleiniger Schwingungsanregung und die Anregung "dunkler Moden" wurden simuliert. Schließlich wurde ein neuer OCT-Algorithmus in Dichtematrixdarstellung entwickelt, der es erlaubt, zeitabhängige Zieloperatoren einzuführen, um nicht nur Kontrolle über den Endzustand einer Anregung, sondern auch über den Anregungsmechanismus zu erlangen. Der Algorithmus basiert auf einer Kombination von globaler (iterativer) und lokaler (nicht-iterativer) optimaler Kontrollschemata in der Art, dass kurze, global kontrollierte Intervalle zeitlich lokal miteinander gekoppelt werden. Nach numerischen Tests wurde der Algorithmus erfolgreich angewandt, um eine Linearkombination aus zwei Zuständen zu stabilisieren, sowie um eine schrittweise "Leiteranregung" in einem harmonischen System zu forcieren, bei dem monochromatische, analytische Pulse mehrere Zustände zugleich anregen und somit einen Populationsverlust im angestrebten Zielzustand zur Folge haben.

A pré-fabricação na arquitetura ainda costuma ser associada à monotonia, repetição, rigidez, e, sobretudo, impossibilidade de participação dos usuários na concepção do produto. Em contraponto a essas associações, dentro de um contexto de expansão global dos sistemas industrializados destinados à construção civil, esse trabalho se propõe a investigar distintas maneiras de aplicar métodos pré-fabricados ao projeto arquitetônico. Faz-se aqui uma análise de três diferentes lógicas de seriação e 5 exibilização utilizadas na produção industrial: o Sistema Fechado, o Sistema Aberto e o Sistema Flexibilizado, buscando-se identi6 car as formas de cada um relacionar-se com o exercício de projeto e em que resultam ou poderiam resultar as diferentes lógicas de seriação e individualização. Objetivando-se identi6 car os fatores que conferem identidade aos projetos face ao emprego de métodos construtivos pré-fabricados, adotou-se, para estudos de caso, a arquitetura de moradia. Tipologia essa que apresenta as relações de maior con5 ito entre individualização e produção seriada. / Prefabrication in architecture is still associated to boredom, repetition, in5 exibility and, mainly, to an impossibility of having users’ participation in the product design. As a counterweight to these associations, within a context of global development of industrialized systems in urban construction, this dissertation proposes an investigation of different ways to apply prefabricated methods to architectural project. Here I do an analysis of three different approaches to serialization and 5 exibilization used in the industrial production: the Closed System, the Open System and the Flexibilized System, trying to identify the way in which each system relates to the execution of the project. I also look at possible results of these different approaches to serialization and individualization. Aiming at specifying the elements which grant identity to the project in terms of the employment of prefabricated building methods, we adopted the housing architecture as case study, since this kind of architecture is the one which presents the biggest con5 icting relations between individualization and serialized production.

A pré-fabricação na arquitetura ainda costuma ser associada à monotonia, repetição, rigidez, e, sobretudo, impossibilidade de participação dos usuários na concepção do produto. Em contraponto a essas associações, dentro de um contexto de expansão global dos sistemas industrializados destinados à construção civil, esse trabalho se propõe a investigar distintas maneiras de aplicar métodos pré-fabricados ao projeto arquitetônico. Faz-se aqui uma análise de três diferentes lógicas de seriação e 5 exibilização utilizadas na produção industrial: o Sistema Fechado, o Sistema Aberto e o Sistema Flexibilizado, buscando-se identi6 car as formas de cada um relacionar-se com o exercício de projeto e em que resultam ou poderiam resultar as diferentes lógicas de seriação e individualização. Objetivando-se identi6 car os fatores que conferem identidade aos projetos face ao emprego de métodos construtivos pré-fabricados, adotou-se, para estudos de caso, a arquitetura de moradia. Tipologia essa que apresenta as relações de maior con5 ito entre individualização e produção seriada. / Prefabrication in architecture is still associated to boredom, repetition, in5 exibility and, mainly, to an impossibility of having users’ participation in the product design. As a counterweight to these associations, within a context of global development of industrialized systems in urban construction, this dissertation proposes an investigation of different ways to apply prefabricated methods to architectural project. Here I do an analysis of three different approaches to serialization and 5 exibilization used in the industrial production: the Closed System, the Open System and the Flexibilized System, trying to identify the way in which each system relates to the execution of the project. I also look at possible results of these different approaches to serialization and individualization. Aiming at specifying the elements which grant identity to the project in terms of the employment of prefabricated building methods, we adopted the housing architecture as case study, since this kind of architecture is the one which presents the biggest con5 icting relations between individualization and serialized production.

A typical automobile system consists of many Electronic Control Units (ECUs) for the purposes of safety, comfort, and entertainment applications. FlexRay is a high bandwidth protocol for such automotive requirements, which facilitates communication between distributed ECUs. This thesis addresses some of the issues associated with the design and implementation of the FlexRay protocol. The number of ECUs that are used in automobiles has an increasing trend to implement more functionality, which demands more bandwidth. By minimizing bandwidth requirements for servicing a given workload of periodic and sporadic real-time tasks, one can connect more ECUs to the same FlexRay bus. With this motivation, the first part of this thesis proposes new algorithms for minimizing bandwidth usage of ECUs in both the static and the dynamic segments of FlexRay. FlexRay provides a time-triggered static segment for the transmission of time critical periodic messages. The static segment consists of a fixed number of static slots each with a fixed duration. The duration of the static slot and the number of slots are design parameters which need to be fixed so as to meet all the deadline requirements of the workload in the application. The static slot duration can be minimized by packing the signals into message frames, while respecting scheduling constraints. Since message frames also contain overhead information, the duration of message frames can be optimized by proper signal packing, based on the network utilization constraints of individual ECUs. The thesis proposes a novel algorithm for packing of signals into message frames and fixing the static slot duration so that the total duration of the static segment is minimized. The dynamic segment of FlexRay caters to the transmission of event-triggered signals. A novel algorithm has been proposed to obtain the minimum duration of the dynamic segment while meeting the deadline constraints of all sporadic messages in their worst-case arrival instances. We also extend all these algorithms to the case of slot multiplexing scheme provided by FlexRay 3.0. Modern automobiles provide infotainment and in-car telemetry functions, which produce a high volume of soft deadline messages. This makes the problem of analyzing scheduling algorithms for such traffic important. The dynamic segment of the FlexRay cycle is used for transmission of such soft deadline messages. The second part of this thesis addresses the issue of analyzing the quality of performance in servicing of the soft deadline tasks in the FlexRay protocol. Two quality measures, namely, the average delay in servicing of the soft deadline tasks and the fraction of tasks that miss their deadlines, are considered. The generation of different soft deadline messages is modeled as independent Poisson processes. The generated messages are queued in different queues and are serviced according to pre-assigned priorities for different queues as per the FlexRay protocol. By analyzing this multiple queue model under some mild assumptions, upper bounds on the arrival rates for different messages are derived so that all the queues are stable. Analytical expressions are also derived for average delay and for deadline miss ratio. The correctness of these approximate analytical expressions are demonstrated through simulation studies.

A pré-fabricação na arquitetura ainda costuma ser associada à monotonia, repetição, rigidez, e, sobretudo, impossibilidade de participação dos usuários na concepção do produto. Em contraponto a essas associações, dentro de um contexto de expansão global dos sistemas industrializados destinados à construção civil, esse trabalho se propõe a investigar distintas maneiras de aplicar métodos pré-fabricados ao projeto arquitetônico. Faz-se aqui uma análise de três diferentes lógicas de seriação e 5 exibilização utilizadas na produção industrial: o Sistema Fechado, o Sistema Aberto e o Sistema Flexibilizado, buscando-se identi6 car as formas de cada um relacionar-se com o exercício de projeto e em que resultam ou poderiam resultar as diferentes lógicas de seriação e individualização. Objetivando-se identi6 car os fatores que conferem identidade aos projetos face ao emprego de métodos construtivos pré-fabricados, adotou-se, para estudos de caso, a arquitetura de moradia. Tipologia essa que apresenta as relações de maior con5 ito entre individualização e produção seriada. / Prefabrication in architecture is still associated to boredom, repetition, in5 exibility and, mainly, to an impossibility of having users’ participation in the product design. As a counterweight to these associations, within a context of global development of industrialized systems in urban construction, this dissertation proposes an investigation of different ways to apply prefabricated methods to architectural project. Here I do an analysis of three different approaches to serialization and 5 exibilization used in the industrial production: the Closed System, the Open System and the Flexibilized System, trying to identify the way in which each system relates to the execution of the project. I also look at possible results of these different approaches to serialization and individualization. Aiming at specifying the elements which grant identity to the project in terms of the employment of prefabricated building methods, we adopted the housing architecture as case study, since this kind of architecture is the one which presents the biggest con5 icting relations between individualization and serialized production.

The last two decades have witnessed a rapid development of various forms of Public-Private Partnerships in Europe. Transport belongs to sectors where PPPs have been most visible and transformative. Yet not all countries have embraced the new method in the same manner. As some initial studies indicate, their PPP readiness varies quite significantly. At the same time, PPP as a product of New Public Management appeared to be in ideological conflict with several new competing paradigms in the field of public policy and public administration. So far, however, no single study has shown how these compatibility issues are dealt with in practice and how (un)successful in reality the European countries are at implementing transport PPPs. This is mostly due to difficulties in formulating appropriate and comparable evaluation criteria. At the same time, with many projects it was simply a bit too early to say whether the original expectations had been met. This study uses a negative definition of PPP success and establishes the failure rate for each country from the sample. In doing so, it only takes into account projects that were abandoned or seriously distressed and modified in advance stages of the procurement process. As a result, transport PPP failure rates of selected European countries are compared. At...

I designed an explanatory sequential mixed-method study to explore the relationship between leadership practices, collective teacher efficacy (CTE), and educational outcomes of low SES students in an open school system. Four data sources were analyzed: K-5 student Developmental Reading Assessment (DRA) results of 1,170 students, Collective Teacher Belief Scale (CTBS) survey to measure CTE perceptions of 48 teachers, focus group interviews composed of a stratified sample of 11 K-5 teachers, and two one-on-one principal interviews. The study took place in two elementary schools in north Texas during the 2020-2021 school year. A Spearman's rank-order correlation analysis indicated that the relationship between CTBS scores and student reading scores was mixed. While one school showed a positive association between CTE and the reading data of low SES students, the other school showed a weak correlation between the variables. The quantitative data indicated that CTBS scores did not independently explain reading achievements at both campuses. The data also showed that while teachers had a large effect size on the reading performance of low SES students, as measured through a Cohen's d for paired sample t-test, achievement gaps continued to widen. Two themes emerged through a grounded theory approach when principals described their sensemaking and framing process: many variables and teamwork. In a complex open system, school principals must consider the many needs of teachers and students before enacting reform efforts. To achieve ambitious goals, school principals promote teamwork and help develop supportive structures to assist teachers and students. Furthermore, the theme of support emerged when teachers described their CTE perceptions concerning their principal's leadership actions. The overall data suggest that leadership practices directly impact CTE levels and indirectly impact student performance. When teachers felt supported, CTE levels increased, but when teachers felt overwhelmed or failed to see how school and district mandates support teaching and learning efforts, CTE levels dropped.