Modern computer hardware platforms are moving towards high core-count and heterogeneous Instruction Set Architecture (ISA) processors to achieve improved performance as single core performance has reached its performance limit. These trends put the current monolithic SMP operating system (OS) under scrutiny in terms of scalability and portability. Proper pairing of computing workloads with computing resources has become increasingly arduous with traditional software architecture. One of the most promising emerging operating system architectures is the Multi-kernel. Multi-kernels not only address scalability issues, but also inherently support heterogeneity. Furthermore, provide an easy way to properly map computing workloads to the correct type of processing resources in presence of heterogeneity. Multi-kernels do so by partitioning the resources and running independent kernel instances and co-operating amongst themselves to present a unified view of the system to the application. Popcorn is one the most prominent multi-kernels today, which is unique in the sense that it runs multiple Linux instances on different cores or group of cores, and provides a unified view of the system i.e., Single System Image (SSI). This thesis presents four contributions. First, it introduces a filesystem for Popcorn, which is a vital part to provide a SSI. Popcorn supports thread/process migration that requires migration of file descriptors which is not provided by traditional filesystems as well as popular distributed file systems, this work proposes a scalable messaging based file descriptor migration and consistency protocol for Popcorn. Second, multi-kernel OSs rely heavily on a fast low latency messaging layer to be scalable. Messaging is even more important in heterogeneous systems where different types of cores are on different islands with no shared memory. Thus, another contribution proposes a fast-low latency messaging layer to enable communication among heterogeneous processor islands for Heterogeneous Popcorn. With advances in networking technology, newest Ethernet technologies are able to support up to 40 Gbps bandwidth, but due to scalability issues in monolithic kernels, the number of connections served per second does not scale with this increase in speed.Therefore, the third and fourth contributions try to address this problem with Snap Bean, a virtual network device and Angel, an opportunistic load balancer for Popcorn's network system. With the messaging layer Popcorn gets over 30% performance benefit over OpenCL and Intel Offloading technique (LEO). And with NetPopcorn we achieve over 7 to 8 times better performance over vanilla Linux and 2 to 5 times over state-of-the-art Affinity Accept. / Master of Science

The re-use of any architecture site, whether it is empty or still holding a presence in remaining elements, creates a connection with the past. Formed by a retaining wall and smokestack, an outdoor room is the destination from which two paths direct the inhabitant. This room divides the site and is surrounded by two buildings designed as a library. Through the use of additional architectural elements, frame and column, the inhabitant is guided along the two paths through visual and physical markers. The inhabitant can either move through the building and find framed views of the smokestack and outdoor room, or move around the building, descending the site towards the outdoor room. This project uses a series of perspective drawings to show the designated paths from the street to the outdoor room. / Master of Architecture

The successful crowdsourcing model and gamification design of Stack Overflow (SO) Q&A platform have attracted many programmers to ask and answer technical questions, regardless of their level of expertise. Researchers have recently found evidence of security vulnerable code snippets being possibly copied from SO to production software. This inspired us to study how reliable is SO in providing secure coding suggestions. In this project, we automatically extracted answer posts related to Java security APIs from the entire SO site. Then based on the known misuses of these APIs, we manually labeled each extracted code snippets as secure or insecure. In total, we extracted 953 groups of code snippets in terms of their similarity detected by clone detection tools, which corresponds to 785 secure answer posts and 644 insecure answer posts. Compared with secure answers, counter-intuitively, insecure answers has higher view counts (36,508 vs. 18,713), higher score (14 vs. 5), more duplicates (3.8 vs. 3.0) on average. We also found that 34% of answers provided by the so-called trusted users who have administrative privileges are insecure. Our finding reveals that there are comparable numbers of secure and insecure answers. Users cannot rely on community feedback to differentiate secure answers from insecure answers either. Therefore, solutions need to be developed beyond the current mechanism of SO or on the utilization of SO in security-sensitive software development. / Master of Science / Stack Overflow (SO), the most popular question and answer platform for programmers today, has accumulated and continues accumulating tremendous question and answer posts since its launch a decade ago. Contributed by numerous users all over the world, these posts are a type of crowdsourced knowledge. In the past few years, they have been the main reference source for software developers. Studies have shown that code snippets in answer posts are copied into production software. This is a dangerous sign because the code snippets contributed by SO users are not guaranteed to be secure implementations of critical functions, such as transferring sensitive information on the internet. In this project, we conducted a comprehensive study on answer posts related to Java security APIs. By labeling code snippets as secure or insecure, contrasting their distributions over associated attributes such as post score and user reputation, we found that there are a significant number of insecure answers (644 insecure vs 785 secure in our study) on Stack Overflow. Our statistical analysis also revealed the infeasibility of differentiating between secure and insecure posts leveraging the current community feedback system (eg. voting) of Stack Overflow.

The purpose of this research is to analyze the statics and dynamics of steel smoke stacks subject to excitation by aerodynamic forces. The wind loads experienced by smoke stacks arise from various phenomenon, the most prominent of which are static drag load, vortex shedding, and atmospheric turbulence. The nature of these loading sources around a cylinder are studied in detail. Both static and dynamic loads are capable of producing large tip deflections, and are of the most prominent design criteria for stack designers. A computer program, STACK1, has been created by modifying an existing analysis code, BEAM8, to be used specifically for stack analysis. This analysis code utilizes the transfer matrix method to perform detailed bending and vibration analyses. This new software has been developed to check stack designs for compliance with appropriate steel stack standards, and provide the designer with information regarding the static and dynamic response of the structure. A detailed analysis is performed to demonstrate the validity of approximating a tapered Timoshenko beam with a series of continuous, constant cross-section beams. / Master of Science

Dans l’objectif d’une augmentation en puissance des piles à combustible pour satisfaire les besoins énergétiques des applications embarquées, une solution consiste à augmenter la taille des assemblages. Dès lors, des problèmes de disparités fluidique, thermique et électrique peuvent survenir dans le cœur des piles et conduire ainsi à l’apparition de défaut. La pile à combustible, de par sa nature de source électrique basse tension – fort courant, requiert d’être couplée au réseau électrique embarqué par l’intermédiaire d’un convertisseur statique. Ce dernier peut alors être employé pour agir de façon corrective sur la pile et aussi de corriger les défaillances qui en sont liées. Dans cette perspective, le convertisseur doit avoir en permanence un retour sur l’état de santé de la pile. Pour cela, une méthode de détection et d'identification de défaut de type noyage et d’assèchement pour une pile du type PEMFC a été approfondie. Cette méthode simple, économique en capteurs, se base sur la mesure de 3 tensions de cellule judicieusement sélectionnées et localisées sur la pile. Ainsi, l’utilisation de l’information « spatiale », qui correspond à la position de la mesure de tension dans la pile permet d’identifier les défauts. Le principe de la détection localisée nous amène alors à considérer le concept de pile segmentée qui consiste à séparer électriquement la pile en 3 parties de façon à ce que des convertisseurs associés puissent agir électriquement sur chaque segment. L’action peut être du type tout ou rien, ou contrôlée. Cette dernière offre davantage de degrés de liberté, et est moins contraignante pour la pile d’un point de vue électrique. Pour choisir comment réaliser cette action, une étude comparative de plusieurs topologies de convertisseur est effectuée. Les structures alimentées en courant répondent au mieux aux contraintes électriques d’une PEMFC et sont donc privilégiées, de même que la nécessité d’une isolation galvanique imposée par la segmentation de la pile. Au final, une topologie de BOOST isolé résonant est apparue comme étant la topologie répondant au mieux à l’ensemble des critères (plage de fonctionnement, performances énergétiques, nombre de composants). L’ensemble convertisseur global intègre ainsi trois structures unitaires qui permettent d'offrir une modularité, une action indépendante sur chaque segment et de garantir une disponibilité du système grâce à un fonctionnement dégradé. Pour cela, la stratégie de commande de l’ensemble convertisseur intègre les informations issues de la méthode de détection. La thèse se termine avec le dimensionnement complet d’un pré-prototype du convertisseur avec le choix des composants actif et passifs, et du système de refroidissement associé. / In the objective of fuel cell power increase in order to satisfy energetic requirements for embedded applications, a solution consists in increasing the size of fuel cell stack assemblies. As possible consequence, fluidic or thermal disparity problems may occur in the fuel cell core and lead to the appearance of faults. The fuel cell, which is a low voltage-high current electrical source, needs to be connected to the on-board electrical network thanks to a static converter. This latter can be used in order to perform a corrective action in the aim of reducing disparities in the stack and also correcting resulting faults. In this perspective, the converter should permanently get information about fuel cell state of health. Hence, a fault detection and identification method for PEMFC has been explored. This method which is simple and requires only few sensors is based on 3 voltage measurements judiciously selected and localized over the stack. Using “spatial” information which corresponds to the position of the sensors, allows to identify some characteristic faults. The principle of the localized fault detection leads to consider the segmentation concept for the fuel cell, which in our case is electrically split into three parts and allows an independent control of each segment by the power converter. Electrical action can be “all or nothing” or moderated ones. The latter offers more degree of freedom, and is less constraining from an electrical point of view. In order to execute the action, study of multiple power converter topologies have been done. Among the candidate topologies, current structures are preferred, as well as the necessity of a galvanic isolation required by the segmentation concept. The resonant isolated boost is the adopted structure; as it meets at best the whole criteria. Thus the global converter assembly is composed of three single structures which offer modularity, independent action on each segment, and continuity of service thanks to degraded modes. The detection method is hence implemented in the converter control strategy. This Ph.D. thesis ends with the complete sizing of a power converter pre-prototype together with technological choices for the active, passive and associated cooling components.

Malgré d'importants progrès ces dix dernières années, les piles à combustible de type PEMFC (à membrane échangeuse de protons) souffrent toujours de fin de vie prématurée. Le catalyseur et la membrane, principaux constituants du cœur de la pile, sont les deux éléments principalement mis en cause. Ce travail a pour objectif de comprendre les modes de rupture et de dégradation de la membrane électrolyte durant le fonctionnement. Différents types de vieillissement ont été analysés, à la fois en laboratoire mais également sur des systèmes ayant fonctionné sur site en conditions réelles d'opération (jusqu'à 13000 heures). Au travers une approche multi-échelle (du système macroscopique à l'analyse des propriétés macromoléculaires de la membrane) et d'une utilisation systématique (plusieurs centaines d'échantillons analysés), des scénarios de dégradation ont été établis. Dans un premier temps, des outils de caractérisation macroscopiques ont été spécifiquement développés pour sonder rapidement l'ensemble des cellules d'un stack. Ces outils permettent d'identifier les défauts inter et intra-cellule tout en discriminant les propriétés barrières aux gaz des propriétés d'isolation électronique des membranes, tous deux responsables des courants de fuite en système. Cette approche systématique sur l'ensemble des échantillons a mis en évidence des zones spécifiques favorisant la dégradation prématurée des membranes. Dans un second temps, des caractérisations physico-chimiques ciblées dans ces zones de défaillance ont révélé une dégradation fortement localisée et principalement favorisée par des conditions opératoires spécifiques dans les zones d'entrée des gaz. / In spite of strong improvements in fuel cell design this last ten years, Proton Exchange Membrane Fuel Cell are still suffering of premature end of life. Failure of the heart of fuel cell, composed of membrane and catalysts, is commonly responsible for fuel cell shutdown. This work brings an original contribution in understanding membrane degradation mechanisms. Different ageing tests were analyzed, in laboratory as well as in real life operating conditions (up to 13000 hours of solicitations). Within a multi-scale approach, from macroscopic to microscopic, and with a systematic usage (hundreds of samples fully characterized), some degradation mechanisms were established. Firstly, macroscopic tools were specifically developed to rapidly track state of health of all the cells from each stack. With the help of these tools, we were able to identify defects inter and intra-cell. It was also possible to discriminate between gas crossover or electronic short-circuit defects, both responsible for current leaks. This systematic approach on each samples put forward some specific areas within the membrane where degradation was promoted. Secondly, physico-chemical characterizations were performed on membrane targeted areas. It was shown that membrane degradation is strongly localized in some specific channels of the bipolar plates and favored by specific operating conditions in the gaz inlets areas.

In this thesis, we consider three parameters associated with graphs : stack number, track number, and layered pathwidth. Our first result is to show that the stack number of any graph is at most 4 times its layered pathwidth. This result complements an existing result of Dujmovic et al. that showed that the queue number of a graph is at most 3 times its layered pathwidth minus one (Dujmovic, Morin, and Wood [SIAM J. Comput., 553–579, 2005]). Our second result is to show that graphs of track number at most 3 have layered pathwidth at most 4. This answers an open question posed by Banister et al. (Bannister, Devanny, Dujmovic, Eppstein, and Wood [GD 2016, 499–510, 2016, Algorithmica, 1–23, 2018]).

No description available.

Internet of Things (IoT) blir allt vanligare i dagens samhälle. Allt fler vardagsenheter blir uppkopplade mot det trådlösa nätet. För det krävs kostnadseffektiv datorkraft vilket medför att det kan vara gynnsamt att undersöka mikrokontroller och hur de skulle klara av detta arbete. Dessa kan ses som mindre kompakta datorer vilka trots sin storlek erbjuder en hel del prestanda. Denna studie avser att underrätta om något befintligt operativsystem kan fungera ihop med mikrokontrollern PIC18F452 samt hur många processer som kan köras parallellt givet MCU:ns begränsade minne. Olika metodval undersöktes och diskuterades för att avgöra vilken metod som skulle generera bäst resultat. En undersökning och flera experiment genomfördes för att kunna besvara dessa frågor. Experimenten krävde att en speciell utvecklingsmiljö installerades och att den generiska FreeRTOS distributionen porterades till både rätt processor och experimentkort. Porteringen lyckades och experimenten visade att frågeställningen kunde besvaras med ett ja - det går att köra ett realtidsoperativsystem på en MCU med enbart 1,5 kB RAM-minne. Under arbetets gång konstaterade också projektet att Amazon byggt sin IoTsatsning på FreeRTOS. De hade dock satsat på en mer kraftfull MCU. Satsningen ville därmed framhålla det som en mer framtidssäker inriktning. / Internet of Things (IoT) is becoming more common in today's society. More and more everyday devices are connected to the wireless network. This requires costeffective computing power, which means that it can be beneficial to investigate the microcontroller and how they would cope with this task. These can be seen as smaller compact computers which despite their size offer a lot of performance. This study aims to inform if any existing operating system can work together with the microcontroller PIC18F452 and how many processes that can run in parallel given the MCU's limited memory. A survey and an experiment were conducted to answer these questions. Different choice of methods was investigated and discussed to determine which method would generate the best results. A survey and an experiment were conducted to answer these questions. The experiments required a special development environment to be installed and the generic FreeRTOS distribution was ported to both the correct processor and the experimental card. The porting succeeded and experiments showed that the research question could be answered with a yes. You can run a real-time operating system on an MCU with only 1,5 kB RAM memory. During the work, the project also found that Amazon built its IoT on FreeRTOS. However, they had invested in a more powerful MCU. The effort would thus emphasize it as a more future-proof approach.

I dagsläget finns det en mängd utmaningar och svårigheter inom den traditio- nella designprocessen för användarupplevelse (UX, User Experience). Dessa utmaningar har en påverkan på hur tidskrävande och kostsam en designpro- cess för UX kan vara. Några av dem är att få prototyper att likna slutpro- dukten och kommunikationssvårigheter mellan UX-designers och utvecklare vid Agil projektmetodik. Några svårigheter som finns vid visualisering av strömmande data är att göra den lättförståelig för användaren och möjliggöra användaren att nå önskad information. För att undersöka dessa svårigheter togs en designprocess för UX, att använ- das med datavisualiseringsverktyget Kibana, fram. För att kunna utvärdera och bedöma designprocessen för UX, skapades en interaktiv dashboard som presenterade Transportstyrelsens data från betalstationer. Framtagningen av designprocessen för UX resulterade i en optimering av prototypskapandet och testningen. Detta eftersom designprocessen för UX möjliggjorde utveckling av produkten, istället för prototypen, vilket förbättrade testningen med slutan- vändaren och därmed även slutprodukten. Det fanns dock nackdelar då Kiba- na användes vilka var begränsningar i modifieringen av användargränssnittet och att systemet behövde vara klart innan designprocessen för UX kunde på- börjas. / In the current situation there are a lot of challenges and difficulties in the traditional design process for UX, User Experience. These challenges have an impact on how time consuming and costly a design process for UX can be. Some of them are to create prototypes that resemble the end product and communication difficulties between UX-designers and developers that follow an Agile project methodology. There are also difficulties in visualizing streaming data, as information in data must be made easy to understand for the user and the users must be able to get desired information. To investigate these difficulties, a design process for UX was created to be used with the Kibana data visualization tool. In order to evaluate and assess the design process for UX, an interactive dashboard was created that pre- sented data from Swedish payment stations. The development of the design process for UX resulted in an optimization of the prototype-creation and test- ing. The design process for UX enabled development of the product, instead of the prototype, which improved the testing with the end user and therefor also the end product. However, there were disadvantages when Kibana was used which were limitations in modifying the user interface and that the sys- tem needed to be ready before the UX design process could begin.