The Quality of Service (QoS) is a profound concept which is gaining increasing attention in the Internet industry. Best-effort applications are now no longer acceptable in certain situations needing high bandwidth provisioning, low loss and streaming of multimedia applications. New emerging multimedia applications are requiring new levels of quality of services beyond those supported by best-effort networks. Quality of service routing is an essential part in any QoS architecture in communication networks. QoS routing aims to select a path among the many possible choices that has sufficient resources to accommodate the QoS requirements. QoS routing can significantly improve the network performance due to its awareness of the network QoS state. Most QoS routing algorithms require maintenance of the global network¿s state information to make routing decisions. Global state information needs to be periodically exchanged among routers since the efficiency of a routing algorithm depends on link-state information accuracy. However, most QoS routing algorithms suffer from scalability due to the high communication overhead and the high computation effort associated with maintaining accurate link state information and distributing global state information to each node in the network. The ultimate goal of this thesis is to contribute towards enhancing the scalability of QoS routing algorithms. Towards this goal, the thesis is focused on Localised QoS routing algorithms proposed to overcome the problems of using global network state information. Using such an approach, the source node makes routing decisions based on the local state information for each node in the path. Localised QoS routing algorithms avoid the problems associated in the global network state, like high communication and processing overheads. In Localised QoS routing algorithms each source node maintains a predetermined set of candidate paths for each destination and avoids the problems associated with the maintenance of a global network state by using locally collected flow statistics and flow blocking probabilities. / Libya's higher education

The localised corrosion behaviour of various grades of Austenitic Stainless Steels has been demonstrated by optical and electron microscopy. The effect of sensitisation upon subsequent corrosive attack has been investigated. A theoretical model based upon thermodynamic and kinetic considerations has been proposed to account for the observed experimental results. / Thesis / Master of Engineering (ME)

Low profile, conformal antennas have considerable advantages for Aerospace and Military platforms where conventional antenna system add weight and drag. Direct Write (DW) technology has been earmarked as a potential method for fabricating low profile antennas directly onto structural components. This thesis determines the key design rules and requirements for DW fabrication of planar antennas. From this, three key areas were investigated: the characterisation of DW ink materials for functionality and durability in harsh environments, localised processing of DW inks and the optimisation of DW conductive ink material properties for antenna fabrication. This study mainly focused on established DW technologies such as micro-nozzle and inkjet printing due to their ability to print on conformal surfaces. From initial characterisation studies it was found that silver based micro-nozzle PTF inks had greater adhesion then silver nano-particle inkjet inks but had lower conductivity (2% bulk conductivity of silver as opposed to 8% bulk conductivity). At higher curing temperatures (>300??C) inkjet inks were able to achieve conductivities of 33% bulk conductivity of silver. However, these temperatures were not suitable for processing on temperature sensitive surfaces such as carbon fibre. Durability tests showed that silver PTF inks were able to withstand standard aerospace environments apart from Skydrol immersion. It was found that DW inks should achieve a minimum conductivity of 30% bulk silver to reduce antenna and transmission line losses. Using a localised electroplating process (known as brush plating) it was shown that a copper layer could be deposited onto silver inkjet inks and thermoplastic PTF inks with a copper layer exhibiting a bulk conductivity of 66% bulk copper and 57% bulk copper respectively. This was an improvement on previous electroless plating techniques which reported bulk copper conductivities of 50% whilst also enabling DW inks to be plated without the need for a chemical bath. One of the limitations of many DW ink materials is they require curing or sintering before they become functional. Conventional heat treatment is performed using an oven which is not suitable when processing DW materials onto large structural component. Previous literature has investigated laser curing as means of overcoming this problem. However, lasers are monochromatic and can therefore be inefficient when curing materials that have absorption bands that differ from the laser wavelength. To investigate this, a laser diode system was compared to a broadband spot curing system. In the curing trials it was found that silver inks could be cured with much lower energy density (by a factor of 10) using the broadband white light source. Spectroscopy also revealed that broadband curing could be more advantageous when curing DW dielectric ink materials as these inks absorb at multiple wavelengths but have low heat conductivity. Themodynamical modelling of the curing process with the broadband heat source was also performed. Using this model it was shown that the parameters required to cure the ink with the broadband heat source only caused heat penetration by a few hundred micro-metres into the top surface of the substrate at very short exposure times (~1s). This suggested that this curing method could be used to process the DW inks on temperature sensitive materials without causing any significant damage. Using a combination of the developments made in this thesis the RF properties of the DW inks were measured after broadband curing and copper plating. It was found that the copper plated DW ink tracks gave an equivalent transmission line loss to a copper etched line. To test this further a number of GPS patch antennas were fabricated out of the DW ink materials. Again the copper plated antenna gave similar properties to the copper etched antenna. To demonstrate the printing capabilities of the micro-nozzle system a mock wireless telecommunications antenna was fabricated on to a GRP UAV wing. In this demonstrator a dielectric and conductive antenna pattern was fabricated on to the leading edge of the wing component using a combination of convection curing and laser curing (using an 808nm diode laser).

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Location and tracking of personnel and assets is a lucrative enterprise that has seen much expansion in the last decade or two. This expansion is coupled with the rise in popularity of GPS-based technologies. It has become common practice for businesses to track and manage vehicle fleets with GPS enabled devices. We use GPS to navigate while driving our cars, to keep track of our loved ones and we even have GPS receivers in our cell phones. Unfortunately, GPS technology has a few limitations. It can only be used in areas with a clear view of the sky, as line-of-sight must be maintained with at least four satellites at all times. This precludes the use of GPS indoors or in heavily built-up areas. GPS receivers are also still quite expensive. This thesis developed and implemented a strategy for Localised Position Location. Several possible solutions were investigated. Spread Spectrum was selected as the best method to develop into a working example. The characteristics of Spread Spectrum signals and Pseudo-Noise Codes were investigated in some detail, which led to the proposal of several simulation models. These simulations suggested that a simple configuration consisting of a transmitter, sliding correlator, bandpass filter and RF power detector can effectively track a stationary target. A transmitter was designed and implemented and was then used in a simplified measurement to corroborate the predictions made by earlier simulations. With results looking positive it was decided to continue with the design and implementation of a receiver. A complete transmitter/receiver system allowed for extensive measurements to be made. The physical measurements agreed with simulated predictions, confirming that the proposed position location strategy is effective. / AFRIKAANSE OPSOMMING: Die toenemende gewildheid en toeganklikheid van GPS-gebaseerde opsporingstegnologie het gelei tot ‘n geweldige toename in die verkope van toerusting om die beweging van besigheidsbates te monitor en bestuur. Selfs op die persoonlike ontspanningsmark vind GPS-tegnologie toenemend aanklank met vervaardigers van selfone en voertuignavigasietoerusting. GPS-gebaseerde opsporingstegnologie het egter beperkinge, omdat dit te alle tye direkte oogkontak moet behou met minstens vier satelliete. Gevolglik kan GPS-gebaseerde opsporingstegnologie nie binnenshuis of in erg beboude gebiede gebruik word nie. GPS ontvangers is ook redelik duur. Hierdie thesis het `n strategie vir Gelokaliseerde Posisie Bepaling ontwikkel en geïmplementeer. Ondersoek is ingestel na `n verskeidenheid van moontlike oplossings. Strek Spektrum is gekies as die beste metode om verder in `n werkende voorbeeld te ontwikkel. Die eienskappe van Strek Spektrum seine en Pseudo-Ruis Kodes is in detail bestudeer, wat gelei het na die opstelling van `n aantal simulasie modelle. Hierdie modelle dui aan dat `n eenvoudige opstelling, bestaande uit `n sender, glykorellator, banddeurlaat filter en `n RF drywingsmeter doeltreffend aangewend kan word om `n stilstaande teiken te monitor. `n Sender, wat in `n vereenvoudigde meetopstelling gebruik kon word om van die voorspellings wat vroeër gemaak is te staaf, is hierna ontwerp en gebou. Met positiewe resultate is daar besluit om voort te gaan met die ontwerp en bou van `n ontvanger. Met `n volledige sender/onvanger stelsel was dit moontlik om uitgebreide meetings te neem. Die fisiese meetings stem ooreen met die simulasies se voorspellings, wat dien as bevestiging dat die voorgestelde strategie vir posisie bepaling doeltreffend aangewend kan word.

The growing demand on the variety of internet applications requires management of large scale networks by efficient Quality of Service (QoS) routing, which considerably contributes to the QoS architecture. The biggest contemporary drawback in the maintenance and distribution of the global state is the increase in communication overheads. Unbalancing in the network, due to the frequent use of the links assigned to the shortest path retaining most of the network loads is regarded as a major problem for best effort service. Localised QoS routing, where the source nodes use statistics collected locally, is already described in contemporary sources as more advantageous. Scalability, however, is still one of the main concerns of existing localised QoS routing algorithms. The main aim of this thesis is to present and validate new localised algorithms in order to develop the scalability of QoS routing. Existing localised routing, Credit Based Routing (CBR) and Proportional Sticky Routing (PSR), use the blocking probability as a factor in selecting the routing paths and work with either credit or flow proportion respectively, which makes impossible having up-to-date information. Therefore our proposed Highest Minimum Bandwidth (HMB) and Highest Average Bottleneck Bandwidth History (HABBH) algorithms utilise bandwidth as the direct QoS criterion to select routing paths. We introduce an Integrated Delay Based Routing and Admission Control mechanism. Using this technique Minimum Total Delay (MTD), Low Fraction Failure (LFF) and Low Path Failure (LPF) were compared against the global QoS routing scheme, Dijkstra, and localised High Path Credit (HPC) scheme and showed superior performance. The simulation with the non-uniformly distributed traffic reduced blocking probability of the proposed algorithms. Therefore, we advocate the algorithms presented in the thesis, as a scalable approach to control large networks. We strongly suggest that bandwidth and mean delay are feasible QoS constraints to select optimal paths by locally collected information. We have demonstrated that a few good candidate paths can be selected to balance the load in the network and minimise communication overhead by applying the disjoint paths method, recalculation of candidate paths set and dynamic paths selection method. Thus, localised QoS routing can be used as a load balancing tool in order to improve the network resource utilization. A delay and bandwidth combination is one of the future prospects of our work, and the positive results presented in the thesis suggest that further development of a distributed approach in candidate paths selection may enhance the proposed localised algorithms.

L'objectif de la thèse est d'étudier le rôle de la structure de gouvernance des « clusters à la française » (pôles de compétitivité, technopoles) sur l'innovation des entreprises membres. Le modèle proposé, d'inspiration néo-institutionnaliste, enrichit les travaux existants sur les déterminants de l'innovation dans les clusters. Il permet d'identifier les pratiques concrètes mises en œuvre par la structure de gouvernance, qui restent largement ignorées dans la littérature, ainsi que leurs effets sur l'innovation. Ces pratiques s'organisent autour de trois principaux leviers : politique, normatif et cognitif. Une analyse comparative est menée sur un technopôle et deux pôles de compétitivité de la région Rhône-Alpes. La méthodologie empirique est basée sur une étude qualitative couplée à une analyse quantitative auprès des membres de la gouvernance et des entreprises des clusters. Les résultats confirment l'impact positif des pratiques de la gouvernance sur l'innovation des entreprises, et ce, quel que soit le type de cluster étudié (pôle de compétitivité et technopole) ». Cet effet varie selon l'intensité de la mobilisation des pratiques et de leur combinaison. Les résultats débouchent sur des indicateurs précis pour un meilleur pilotage « des clusters à la française ». / The aim of this thesis is to study the role of cluster governance in the innovation of firms belonging to French clusters (technopole and competitiveness cluster). The proposed conceptual model, based on a neo-institutional approach, refines existing works on the determinants of innovation in clusters. It enables the precise identification of concrete practices implemented by cluster governance, largely ignored in current literature on clusters, as well as their effects on innovation. These practices are organised around three main levers: political, normative and cognitive. A comparative analysis is carried out on three French clusters of the Rhône-Alpes region: one technopole and two competitiveness clusters. The empirical methodology is based on a qualitative study combined with a quantitative analysis of members of cluster governance and firms. Our main results confirm the positive impact of cluster governance practices on firms' innovation, irrespective of the type of French cluster (technopole or competitiveness cluster). This effect varies according to the intensity of the practices' mobilisation as well as their combination. These results have main implications in terms of public policy: in particular, they provide key monitoring indicators for a better management of French clusters.

This thesis presents the results of a research project to develop methods to carry out fire safety design of welded steel tubular trusses at elevated temperatures due to fire exposure. It deals with three subjects: resistance of welded tubular joints at elevated temperatures, effects of large truss deflection in fire on member design and effects of localised heating. The objectives of the project are achieved through numerical finite element modelling at elevated temperatures using the commercial Finite Element software ABAQUS v6.10-1 (2011). Validation of the simulation model for joints is based on comparison against the test results of Nguyen et al. (2010) and Kurobane et al. (1986). Validation of the simulation model for trusses is through checking against the test results of Edwards (2004) and Liu et al. (2010).For welded tubular joints, extensive numerical simulations have been conducted on T-, Y-, X-, N- and non-overlapped K-joints subjected to brace axial compression or tension, considering a wide range of geometrical parameters. Uniform temperature distribution was assumed for both the chord and brace members. Results of the numerical simulations indicate for gap K- and N-joints (two brace members, one in tension and the other in compression) and for T-, Y- and X-joints with the brace member under axial tensile load (one brace member only, in tension), it is suitable to use the same ambient temperature calculation equation as in the CIDECT (2010) or EN 1993-1-8 (CEN, 2005a) design guides and simply replace the ambient temperature strength of steel with the elevated temperature value. However, for T-, Y- and X-joints under brace compression load (one brace member only, in compression), the effect of large chord deformation should be considered. Large chord deformation changes the chord geometry and invalidates the assumed yield line mechanism at ambient temperature. For approximation, the results of this research indicate that it is acceptable to modify the ambient temperature joint strength by a reduction factor for the elastic modulus of steel at elevated temperatures. In the current fire safety design method for steel truss, a member based approach is used. In this approach, the truss member forces are calculated at ambient temperature based on linear elastic analysis. These forces are then used to calculate the truss member limiting temperatures. An extensive parametric study has been carried out to investigate whether this method is appropriate. The parametric study encompasses different design parameters over a wide range of values, including truss type, joint type, truss span-to-depth ratio, critical member slenderness, applied load ratio, number of brace members, initial imperfection and thermal elongation. The results of this research show that due to a truss undergoing large displacements at elevated temperatures, some truss members (compression brace members near the truss centre) experience large increases in member forces. Therefore, using the ambient temperature member force, as in the current truss fire safety design method, may overestimate the truss member critical temperature by 100 °C. A method has been proposed to analytically calculate the increase in brace compressive force due to large truss deformation. In this method, the maximum truss displacement is assumed to be span/30. A comparison of the results calculated using the proposed method against the truss parametric study results has shown good agreement with the two sets of results, with the calculation results generally being slightly on the safe side. When different members of a truss are heated to different temperatures due to localised fire exposure, the brace members in compression experience increased compression due to restrained thermal expansion. To calculate the critical temperature of a brace member in a localised heated truss, it is necessary to consider this effect of restrained thermal expansion. It is also necessary to consider the beneficial effects of the adjacent members being heated, which tends to reduce the increase in compressive force in the critical member under consideration. Again, an extensive set of parametric studies have been conducted, for different load ratio, slenderness and axial restraint ratio. The results of this parametric study suggest that to calculate the critical temperature of a brace member, it is not necessary to consider the effects of the third or further adjacent members being heated. For the remainder of the heated members, this thesis has proposed a linear elastic, static analysis method at ambient temperature to calculate the additional compressive force (some negative, indicating tension) in the critical member caused by the heated members (including the critical member itself and the adjacent members). The additional compressive force is then used to calculate the limiting temperature of the critical member. For this purpose, the approximate analytical equation of Wang et al. (2010) has been demonstrated to be suitable.

Cette thèse a porté sur la conception d'un capteur de corrosion passif, sans contact de moyenne portée. Les solutions existantes sans fil concernent soit des capteurs à architecture classique, soit des solutions passives. Dans le premier cas, le capteur de corrosion est actif et peut être interrogé à longue portée. Dans le second cas, les solutions passives existantes ne fonctionnent qu’avec des distances de lecture de quelques centimètres du fait des basses fréquences utilisées. L’objectif de ce travail était de répondre à ce besoin. Pour cela, nous nous sommes inspirés de la technologie RFID (Radio Frequency Identification) passive chipless pour le développement d’un capteur basé sur une fonction hyperfréquence. La première structure réalisée a été une ligne microruban, dont le ruban est constitué d’une couche mince d’un élément sensible à la corrosion. Dans ce cas, la corrosion de la ligne s’est traduite par une variation d’amplitude du fait de l’apparition de pertes expliquées principalement par l’effet de peau ou la création de défauts. Une deuxième structure hyperfréquence a été élaborée en se basant sur un stub (circuit ouvert) qui a permis de suivre le processus de la corrosion via une variation de fréquence. Comme le cas de la ligne microruban, cette structure nous a permis de distinguer la corrosion uniforme et la corrosion localisée. Grâce à la mise en évidence de ces fonctionnalités, diverses stratégies de contrôle de la corrosion peuvent être imaginées et un démonstrateur a été réalisé. Le point clé du démonstrateur proposé est une augmentation de la distance de lecture dans la technologie RFID chipless, ceci a été rendu possible en considérant l’isolation Tx / Rx du lecteur. Dans ce contexte, trois types d’antennes ont été étudiées. Afin d’augmenter encore la distance de lecture, d’autres techniques d’isolation ont été proposées : l’utilisation d’un déphaseur mais aussi l’isolation temporelle par l’utilisation d’une ligne à retard SAW. Grâce à ces 2 méthodes, une distance de lecture de deux mètres a été obtenue. Suite aux caractérisations RF des métaux soumis à la corrosion discutées, nous avons aussi élaboré une sonde RF à champ proche permettant de diagnostiquer la corrosion de surfaces métalliques. / This thesis focused on the design of a passive wireless corrosion sensor. Existing wireless solutions concern either classic architecture sensors or passive solutions. In the first case, the corrosion sensor is active and can be interrogated at long range. In the second case, the existing passive solutions only work with reading distances of a few centimeters because of the low frequencies. The objective of this study was to respond to this need. That’s why; we were inspired by the RFID( Radio Frequency Identification) passive chipless technology for the development of a sensor based on a microwave function. The first structure was a microstrip line, of which the strip is composed of a thin layer of an element sensitive to corrosion. In this case, the corrosion of the line is proven by an amplitude variation due to losses principally explained by the skin effect or the creation of defects. A second microwave structure was developed based on a stub (open circuit) which allowed us to follow the process of corrosion via a frequency variation. Much like the microstrip line, this structure allowed us to distinguish between uniform corrosion and localised corrosion. Due to the highlighting of these features, different corrosion control strategies can be imagined and a demonstrator was executed. The key point of the proposed demonstrator is an increase in the reading distance in the chipless RFID technology; this was made possible by taking into consideration the isolation TX / Rx of the reader. In this context, three types of antennas were studied. In order to increase the reading distance, other isolation techniques were proposed: the use of a phase shifter but also a temporal isolation using a SAW delay line. Thanks to these two methods, a reading distance of two meters was obtained. Following the RF characterizations of metals exposed to the discussed corrosion, we also developed a near field RF probe, which allows corrosion diagnostic of metal surfaces.

The growing demand on the variety of internet applications requires management of large scale networks by efficient Quality of Service (QoS) routing, which considerably contributes to the QoS architecture. The biggest contemporary drawback in the maintenance and distribution of the global state is the increase in communication overheads. Unbalancing in the network, due to the frequent use of the links assigned to the shortest path retaining most of the network loads is regarded as a major problem for best effort service. Localised QoS routing, where the source nodes use statistics collected locally, is already described in contemporary sources as more advantageous. Scalability, however, is still one of the main concerns of existing localised QoS routing algorithms. The main aim of this thesis is to present and validate new localised algorithms in order to develop the scalability of QoS routing. Existing localised routing, Credit Based Routing (CBR) and Proportional Sticky Routing (PSR), use the blocking probability as a factor in selecting the routing paths and work with either credit or flow proportion respectively, which makes impossible having up-to-date information. Therefore our proposed Highest Minimum Bandwidth (HMB) and Highest Average Bottleneck Bandwidth History (HABBH) algorithms utilise bandwidth as the direct QoS criterion to select routing paths. We introduce an Integrated Delay Based Routing and Admission Control mechanism. Using this technique Minimum Total Delay (MTD), Low Fraction Failure (LFF) and Low Path Failure (LPF) were compared against the global QoS routing scheme, Dijkstra, and localised High Path Credit (HPC) scheme and showed superior performance. The simulation with the non-uniformly distributed traffic reduced blocking probability of the proposed algorithms. Therefore, we advocate the algorithms presented in the thesis, as a scalable approach to control large networks. We strongly suggest that bandwidth and mean delay are feasible QoS constraints to select optimal paths by locally collected information. We have demonstrated that a few good candidate paths can be selected to balance the load in the network and minimise communication overhead by applying the disjoint paths method, recalculation of candidate paths set and dynamic paths selection method. Thus, localised QoS routing can be used as a load balancing tool in order to improve the network resource utilization. A delay and bandwidth combination is one of the future prospects of our work, and the positive results presented in the thesis suggest that further development of a distributed approach in candidate paths selection may enhance the proposed localised algorithms. / Umm AlQura University in Mecca

La thèse traite de recherches numériques et expérimentales sur l’écoulement à traves des conduites circulaires ou des tubes avec une petite entrée et un diamètre de sortie plus grand, parfois appelées élargissement ou divergents. L’écoulement dans un élargissement est globalement stable pour des nombres de Reynolds élevés. Ainsi la simulation numérique de ce type d’écoulement nécessite de grands domaines de calcul contenant la zone de recirculation, qui croît linéairement. En outre, les études expérimentales dans les élargissements brusques indiquent que la transition se produit à des nombres de Reynolds plus faibles que prévue par la théorie linéaire de stabilité. La raison pour cette transition précoce est due à la présence d’imperfections dans le dispositif expérimental, qui agit comme une perturbation d’amplitude finie de l’écoulement. Des simulations numériques directes des équations de Navier-Stokes ont été réalisées avec deux types différents de perturbations (i) l’inclination et (ii) le vortex. Tout d’abord, la perturbation de type inclinaison, qui est appliqué à l’entrée, crée une zone de recirculation asymétrique, puis se casse pour former une turbulence localisée en aval de l’expansion. Deuxièmement, la perturbation de type vortex, crée des structures qui ressemblent à un mode azimutal d’ordre inférieur, déjà identifié comme une perturbation optimale amplifiée. Il croît en raison de l’instabilité convective, puis forme une tâche de turbulence localisée. Enfin, la corrélation spatiale et la décomposition en modes propres révèlent que cette turbulence localisée obtient son énergie de l’écoulement d’entrée. / The thesis deals with numerical and experimental investigations of flow through circular pipes with smaller inlet and larger outlet diameter, also known as expansion pipes. The hydrodynamic expansion pipe flow is globally stable for high Reynolds number. In order to numerically simulate these types of flows, large computational domains that could accommodate the linearly growing symmetric recirculation region is needed. Moreover, experimental studies of expansion pipe flows indicate that the transition occurs at lower Reynolds number than predicted by the linear stability theory. The reason for early transition is due to the presence of imperfections in the experimental setup, which acts as a finite-amplitude perturbation of the flow. Three-dimensional direct numerical simulations of the Navier-Stokes equations with two different types of perturbations (i) the tilt and (ii) the vortex are investigated. First, the tilt perturbation, which applied at the inlet, creates an asymmetric recirculation region and then breaks to form localised turbulence downstream the expansion section. Second, the vortex perturbation, creates structures that looks like lower order azimuthal mode, resembles an optimally amplified perturbation. It grows due to convective instability mechanism and then breaks to form localised turbulence. Spatial correlation and the proper orthogonal decomposition reveal that this localised turbulence gains it energy from the core flow coming out of the inlet pipe.