La croissance rapide du trafic aérien et les besoins en nouveaux services notamment pour les passagers imposent l'introduction de nouveaux moyens de communication pour les avions avec une bande passante globale fortement accrue. Les satellites sont appelés à jouer un rôle important dans ce contexte, non seulement en complément des systèmes terrestres pour les services « cockpit » (services ATM, Air Traffic Management) mais aussi pour les services « cabine » (In-Flight Entertainment). L'objectif de la thèse est d'étudier l'architecture d'un système satellite supportant l'ensemble de ces services, en se focalisant sur l'architecture du terminal embarqué à bord des aéronefs. L'architecture retenue repose sur des liaisons DVB-S2/DVB-RCS normalisées par l'ETSI. Cette option permet d'utiliser efficacement l'importante bande passante disponible en bande Ka pour les services mobiles aéronautiques (allocation primaire) ou en bande Ku (allocation secondaire). Ces normes ont été conçues pour les applications multimédia (Broadband Satellite Multimedia). Le défi est alors d'utiliser de telles liaisons satellite pour des services aux caractéristiques et besoins fortement hétérogènes. Par ailleurs, l'utilisation de la bande Ka n'est pas concevable sans l'activation de techniques de lutte contre les affaiblissements (FMT – Fade Mitigation Techniques). L'utilisation d'une marge statique conduit à une perte importante de capacité. Les techniques FMT reposent sur une évaluation dynamique du bilan de liaison et permettent une modification de la forme d'onde. Le système utilise ainsi la forme d'onde la plus efficace spectralement pour chaque terminal et maximise la capacité globale du système. Par contre, chaque terminal observe une modification de la ressource allouée au fil du temps. L'objectif de la thèse est de concevoir une architecture au niveau terminal qui permette d'exploiter les liaisons DVB-S2/RCS afin de fournir les services passagers (Internet et téléphonie mobile de type GSM/UMTS) et un canal haute fiabilité pour les services aéronautiques. Deux approches ont été retenues. La première repose sur une application du modèle ETSI BSM (Broadband Satellite Multimedia) en couches séparant strictement les couches dépendantes satellite et les couches indépendantes satellite. Les simulations de cette architecture montrent que les liaisons ne peuvent être utilisées de façon efficace sans une interaction entre couches afin de tenir compte de l'évolution de la capacité disponible. La seconde approche consiste en la concentration de la gestion de la ressource et la gestion de la qualité de service dans la même couche protocolaire. L'idée de départ est d'utiliser la méthode d'encapsulation générique Generic Stream Encapsulation (GSE). GSE a été conçu pour la projection des paquets de couches supérieures à l'intérieur des trames DVB-S2. GSE tient compte de la taille variable des trames DVB-S2 et introduit une capacité de multiplexage entre différents flux (identification de fragments). Sur cette base, une gestion de l'accès est introduite pour gérer la liaison DVB-RCS au format MF-TDMA. Nous introduisons ainsi une utilisation conjointe de GSE, d'une politique de service différentiée et de flux de signalisation inter-couches (« cross-layer »). Les performances des deux approches sont étudiées à l'aide d'un modèle de simulation développé à l'aide du logiciel OPNET Modeler (simulations à événements discrets). Les résultats obtenus démontrent le meilleur comportement de la seconde architecture avec une meilleure utilisation de la ressource et des performances de transmission satisfaisant les objectifs. / The rapid growth of air traffic needs a new communication infrastructure with increased bandwidth, high speed services and applications to satisfy expected air-ground communication requirements. Satellite communication systems play a significant role in this context, not only as a complement to terrestrial systems for Air Traffic Management (ATM) by offering global coverage but also as a promising solution to enrich In-Flight Entertainment (IFE) for passengers. DVB-S2/RCS technology is an attractive proposition to provide the cost-effective broadband services for both ATM and IFE, mainly because a large radio bandwidth is primarily allocated to aeronautical mobile communications in Ka-band, where the open standards DVB are implemented. However, such system design with convergence of heterogeneous traffics involves two main challenges. Firstly, using Ka-band means the implementation of Fade Mitigation Techniques (FMT) in order to cope with deep fades caused by atmospheric attenuation. Otherwise, the waste of capacity would be excessively high in a constant link margin design. FMT adapt in real time the link budget to the propagation conditions, this adaptivity has an impact not only on physical layer but also on upper layers. An efficient ressource management strategy with dynamic bandwidth allocation is required in this case, especially in DVB-RCS return link where FMT are not natives. Secondly, the proposed system must be able to multiplex the trafic flows with highly different characteristics and Quality of Service (QoS) expectations into a single link, the corresponding capacity management and QoS support seem with higher complexity. In this paper, we present an adaptive system design using a single DVB-S2/RCS based satellite link to provide Internet access and mobile telephony (GSM/UMTS) for passengers and a high-reliability channel for ATM. Concerning the airborne terminal architecture, two approaches are investigated. The first one is in compliance with ETSI Broadband Satellite Multimedia (BSM) architecture and based on a layering paradigm. The conducted simulation experiments highlight the need of dynamic interactions and adaptations among the layers to achieve an overall performance optimization. We propose then an enhanced approach with the concentration of both resource allocation and QoS management at the same interface – adaptation layer. The idea comes from the success of the recent Generic Stream Encapsulation (GSE) protocol, which carries the network protocol packets over DVB-S2 forward link in a simple, flexible and efficient way, especially when used with Adaptive Coding and Modulation (ACM). Furthermore, GSE can be easily extended to use in our design for DVB-RCS return link thanks to a proper design of MF-TDMA structure in which the suitable FMT (ACM and Dynamic Rate Adaptation) are context-aware configured. With the combined use of GSE, service policy and the interactions between adaptation and access layers, incoming heterogeneous traffics can be dynamically scheduled, segmented and encapsulated at the same adaptation layer. Performance evaluation of two proposed approaches is derived by a network-level simulation model developed using OPNET. Results prove the enhanced approach outperforms the first one leading to better resource utilization and satisfactory performance.

abstract: Impedance-modulated metasurfaces are compact artificially-engineered surfaces whose surface-impedance profile is modulated with a periodic function. These metasurfaces function as leaky-wave antennas (LWAs) that are capable of achieving high gains and narrow beamwidths with thin and light-weight structures. The surface-impedance modulation function for the desired radiation characteristics can be obtained using the holographic principle, whose application in antennas has been investigated extensively. On account of their radiation and physical characteristics, modulated metasurfaces can be employed in automotive radar, 5G, and imaging applications. Automotive radar applications might require the antennas to be flush-mounted on the vehicular bodies that can be curved. Hence, it is necessary to analyze and design conformal metasurface antennas. The surface-impedance modulation function is derived for cylindrically-curved metasurfaces, where the impedance modulation is along the cylinder axis. These metasurface antennas are referred to as axially-modulated cylindrical metasurface LWAs (AMCLWAs). The effect of curvature is modeled, the radiation characteristics are predicted analytically, and they are validated by simulations and measurements. Communication-based applications, like 5G and 6G, require the generation of multiple beams with polarization diversity, which can be achieved using a class of impedance-modulated metasurfaces referred to as polarization-diverse holographic metasurfaces (PDHMs). PDHMs can form, one at a time, a pencil beam in the desired direction with horizontal polarization, vertical polarization, left-hand circular polarization (LHCP), or right-hand circular polarization (RHCP). These metasurface antennas are analyzed, designed, measured, and improved to include the ability to frequency scan. In automotive radar and other imaging applications, the performance of metasurface antennas can be impacted by the formation of standing waves due to multiple reflections between the antenna and the target. The monostatic RCS of the metasurface antenna is reduced by modulating its surface impedance with a square wave, to avert multiple reflections. These square-wave-modulated metasurfaces are referred to as checkerboard metasurface LWAs, whose radiation and scattering characteristics, for normal incidence parallel polarization, are analyzed and measured. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2020

abstract: Within the past two decades, metasurfaces, with their unique ability to tailor the wavefront, have attracted scientific attention. Along with many other research areas, RADAR cross-section (RCS)-reduction techniques have also benefited from metasurface technology. In this dissertation, a novel technique to synthesize the RCS-reduction metasurfaces is presented. This technique unifies the two most widely studied and two well-established modern RCS-reduction methods: checkerboard RCS-reduction andgradient-index RCS-reduction. It also overcomes the limitations associated with these RCS-reduction methods. It synthesizes the RCS-reduction metasurfaces, which can be juxtaposed with almost any existing metasurface, to reduce its RCS. The proposed technique is fundamentally based on scattering cancellation. Finally, an example of the RCS-reduction metasurface has been synthesized and introduced to reduce the RCS of an existing high-gain metasurface ground plane. After that, various ways of obtaining ultrabroadband RCS-reduction using the same technique are proposed, which overcome the fundamental limitation of the conventional checkerboard metasurfaces, where the reflection phase difference of (180+-37) degrees is required to achieve 10-dB RCS reduction. First, the guideline on how to select Artificial Magnetic Conductors (AMCs) is explained with an example of a blended checkerboard architecture where a 10-dB RCS reduction is observed over 83% of the bandwidth. Further, by modifying the architecture of the blended checkerboard metasurface, the 10-dB RCS reduction bandwidth increased to 91% fractional bandwidth. All the proposed architectures are validated using measured data for fabricated prototypes. Critical steps for designing the ultrabroadband RCS reduction checkerboard surface are summarized. Finally, a broadband technique to reduce the RCS of complex targets is presented. By using the proposed technique, the problem of reducing the RCS contribution from such multiple-bounces simplifies to identifying and implementing a set of orthogonal functions. Robust guidelines for avoiding grating lobes are provided using array theory. The 90 degree dihedral corner is used to verify the proposed technique. Measurements are reported for a fabricated prototype, where a 70% RCS-reduction bandwidth is observed. To generalize the method, a 45 degree dihedral corner, with a quadruple-bounce mechanism, is considered. Generalized guidelines are summarized and applied to reduce the RCS of complex targets using the proposed method. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2020

This diploma thesis is aimed at radar cross section of passenger cars. Basic scattering parameters of simple targets are described. Selected numeric methods used for computing radar cross section are discussed. Shape and size of simplified vehicle models is investigated. Simulations are verified by computing RCS of objects with well-known characteristics. Radar cross section of Skoda Octavia was simulated using selected numeric methods. Results of all performed simulations are shown in included graphs. Experimental measurment of radar cross section of a vehicle was performed so the measured data can be compared with the simulations.

When designing military vehicles, it is of interest to make the vehicles difficult to detect using radar. The radar cross-section (RCS) property indicates how easily a vehicle is detected by radar and should thus be minimized. However, the RCS of a vehicle represents the cross-sectional area of a perfectly reflecting sphere that would produce the same reflection strength as the vehicle in question. Since this is extremely complicated to calculate as military vehicles are quite complex, these calculations are performed using computational simulations. BAE Systems Hägglunds is looking into changing from their current simulation software OPTISCAT to CST Studio Suite and thus want to know how CST performs and compares against OPTISCAT. In this work, we show that CST obtains results within 2% of theoretical data when simulating a sphere and a slab. When simulating vehicles, the RCS difference between the two software is from 3% to 55% while showing similar general behavior. Results indicate that CST performs well when simulating simple objects but deviates from OPTISCAT when simulating the vehicle. It is not surprising that the software does not match up perfectly since they use different theoretical approaches, OPTISCAT uses physical optics while CST an extension to physical optics called the Shooting Bouncing Ray method. Even though the software differs to this extent it is most likely possible that CST can be a suitable replacement for OPTISCAT. When looking at RCS the important part is the location of spikes and since they have similar general behavior, those spikes may still be possible to identify. This thesis will hopefully act as a starting point for further examination of CST as a software for simulating RCS, for example by comparing results from CST to experimentally measured data. Hopefully it will also be used to improve the design process of making military vehicles harder to detect.

The Rich Communication Service (RCS) aims to be the default messaging protocol in mobile devices. The native integration of RCS opens up the possibility of RCS chatbots replacing single-purpose apps. This report analyzes this possibility through in-depth experimentation of the chatbot functionality, followed by user testing of the chatbot features. The report found that the RCS chatbot could replace mobile applications since many solve a specific task and follow a closed-loop system. The report also identified RCS as a solution to the accumulated unused apps users have on their mobile devices. This report also attempts to fill the research gap on the current situation of RCS and the reasons behind the different rollout rates of RCS globally. The examination of interviews with RCS stakeholders was the basis of a stakeholder analysis. This analysis found that the Mobile Network Operators have different standings regarding RCS. Some see potential, and some see issues with RCS hindering the global rollout. Furthermore, the reluctance from Apple and the high involvement of Google are reviewed and contrasted with the answers from the interviews. / Rich Communication Service (RCS) siktar på att bli det nya standardprotokollet för att skicka meddelanden mellan mobiler. RCS potentiella integration i mobilens egna meddelande applikation öppnar upp för möjligheten att RCS- chatbotar även kan ersätta enklare appar med begränsade användningsområden. Denna rapport undersöker den här möjligheten genom experimenterande med chatbotens funktionalitet följt av användartester på chatbotens olika funktioner. Rapporten fann att chatboten i RCS har goda möjligheter att ersätta enklare mobila applikationer då många löser specifika uppgifter som följer ett system med en sluten slinga. Rapporten identifierade även RCS som en lösning till den mängd oanvända appar som användare har i sina mobiler. Denna rapport försöker även fylla det forskningsgap som finns angående RCS nuvarande situation och anledningarna till de olika adoptionshastigheterna i världen. Granskning av de intervjuer som hölls med olika intressenter på marknaden blev grunden för den intressentanalys som presenteras. Denna analys visade att teleoperatörer har olika ställningar gentemot RCS. Vissa ser potential medan andra främst ser problem vilket hindrar spridningen av RCS. Dessutom analyserades Apples ovilja att anamma RCS samt Googles

Previous research discovered the existence of sedimentation-resistant mutants of E. coli. Genomic studies revealed that these mutants resisted sedimentation due to independent modifications to genes that influenced the Rcs signal transduction pathway, causing increased secretion of an exopolysaccharide capsule comprised primarily of colanic acid. The Rcs system is responsible for detecting envelope stressors; consequently, ampicillin and osmotic stress were used to perturb the cellular envelope and study the response of the mutants compared to wild-type cells. It was found that the overproduction of colanic acid in the mutants confers some resistance to envelope stress; however, the mutants still behaved similarly to wild-type cells. The doubling times of the strains grown in sodium chloride solutions were calculated. A wavelength scan from 400 nm to 800 nm was performed on strains grown in different salt concentrations to determine if there were significant differences in light scattering between the wild-type and mutant cells. Further analysis was performed that, along with the doubling time data, suggested that wild-type cells may have turned on genes for capsule production in response to being grown in high salt concentrations. Additional research could be conducted to test this hypothesis, perhaps through the quantification of colanic acid through a methyl pentose assay for wild-type cultures grown with high salt concentrations. The idea that wild-type cells could digest colanic acid as a carbon source when lacking resources was also investigated with different preparations of colanic acid. One preparation of colanic acid showed promising results, which could indicate that bacteria are able to digest their capsule in a novel method to produce energy when starved. Again, additional investigation should be conducted to confirm these results. Other future experiments could study the metabolome of these mutants to determine if they have increased quantities of alarmones related to biofilm formation.

Pinus mugo Turra (sensu lato) is a prostrate shrub growing above the alpine timberline in the mountain ranges of Southern, Central and Eastern Europe. It is well adapted to the harsh alpine environment creating different mechanisms for survival. The research was carried out in Krkonoše Mountains on base of Pinus mugo individuals compared with Picea abies trees. Samples from shrubs were gathered using serial sectioning from four sites in different elevations located on Sněžka Mountain and Smogornia Ridge. Further analysis of the sampled material was made with the help of different detrending methods to see which method will return the best growth response to climate parameters. RCS detrending and detrending via simple averaging reflected the best climate signal contained in dwarf pine chronologies. The advantage of these methods is based on their ability to reflect growth conditions of the particular site. Upper sites showed significant correlations with temperatures of the growing season, while on lower sites the signal was quite unclear. The amount of precipitation plays the significant role on shrub growth during the vegetation period (especially July month) and early spring when water is very important for growth initiation. Upper Pinus mugo sites showed high sensitivity to droughts, especially...

Detta examensarbete har utförts i samarbete med Löfqvist Engineering i Örebro. Uppgiften har varit att utföra en simulering av en stor automatiserad produktionslina som ska användas vid tillverkning av avgassystem till lastbilar. Utifrån denna simulering skall exakta cykeltider för produktionen bestämmas. Dessa tider kan sedan användas av Löfqvist Engineering för att verifiera tidigare uppskattade tider. Arbetet inkluderar en litteraturstudie om Lean Production och hur det fungerar ihop med automation. Det finns även med lite bakgrundsinformation om Just In Time, olika filformat och robotsimulering i allmänhet för att ge en bättre överblick av ämnet. Programmet som har valts för att utföra simuleringen är Tecnomatix Process Simulate och den inbyggda Line Simulation modulen. Produktionslinan består av fyra hanteringsrobotar, 13 operatörsstationer och åtta identiska svetsceller. Cykeltider för produktionslinan har bestämts och resultatet blev 6 min 31 s, så det tar alltså lite drygt 6,5 minuter för produktionslinan att leverera en ny produkt. Cykeltiderna bestämdes genom att beräkna medelvärde på tiden det tog att framställa 10 stycken produkter då linan var full av material. I rapporten finns beskrivet hur arbetet för att komma fram till cykeltiderna har fortgått och hur simuleringsproblemen som uppstått under arbetets gång har lösts. / This thesis has been carried out in collaboration with Löfqvist Engineering in Örebro. The task has been to perform a simulation of a large automation line, to be used in the manufacture of exhaust systems for trucks. Based on this simulation accurate cycle times for production are determined. These times can then be used by Löfqvist Engineering to verify the earlier estimated times. The work includes a literature review of Lean Production and how it works with automation. There is also some background information on Just In Time, different file formats and robot simulation in general for the reader to get a bit more background knowledge of the subject. The program that has been selected to perform the simulation is Tecnomatix Process Simulate and its built in Line Simulation module. The automation line consists of four handling robots, 13 operator stations and eight identical welding cells. Cycle times for the automation line have been determined and the result was 6 min 31s, for the automation line to complete one product. Cycle times were determined by calculating the average time to produce 10 pieces of products when the line was full of material. The report describes how the work for arriving at these cycle times have been performed and how simulation problems encountered during such operations have been resolved.

The aim of the thesis is conceptual design of robotic workplace with its subsequent simulation. The current workplace for manufacturing and deburring parts for automotive industry is operated manually. The plan is overall automation and replacement of operators by robots. The thesis deals with the concept of layout of elements in the cell, and the procedure of their selection or design. Process simulation is performed in the Process Simulate software from Siemens. For the purposes of the work is used RCS module, which on the basis of dynamic conditions can calculate the cycle of production very close to the reality. The production cycle is compared to the current workplace. The work also deals with the economic evaluation of the proposed workplace.