A circular cylinder is a geometrically simple bluff body that occurs in various practical applications. As with any bluff body, it exhibits large drag forces and a strong fluctuating lift force, both related to the strong shedding of vortices from the body, which is commonly referred to as the Karman Street. Rigid splitter plates in the wake of the cylinder are known to suppress shedding from the body, and thereby result in reduced drag and fluctuating lift forces, the latter being important to reduce flow-induced vibrations of the body. In the present work, the flow past a cylinder with a downstream flexible splitter plate/flap is studied, the length (L) and flexural rigidity (EI) of the flap being the main parameters besides the flow speed (U). Two flaps length to cylinder diameter ratios (L/D), namely, a short (L/D = 2) and a long (L/D = 5) flaps have been studied, the shorter one being smaller than the recirculation zone, while the larger is longer than the recirculation zone. In both these cases, the flexural rigidity (EI) and the flow speed are systematically varied. In all cases, the flaps motion are directly visualized, the lift and drag forces are measured with a force balance, and the wake velocity field is measured using PIV. In both the long and short flaps cases, the flexural rigidity (EI) of the flexible flap has been varied over a large range of values, and it has been found that the results for flaps tip motion and forces collapse well when plotted with a non-dimensional bending stiffness (K∗), which is defined as K∗ = EI/(1/2ρU2L3). This collapse occurs across flexible flaps with different values of EI, as long as Re > 5000. The collapse is not found to be good for Re < 5000. This difference appears to be related to the large reduction in fluctuating lift for a bare cylinder in the Re range between approximately 1600 and 5000 discussed by Norberg[41]. In the long flap case, the existence of two types of periodic modes is found within the range of K∗ values from 5 × 10−6 to 1 × 10−1 studied. The first one corresponds to a local peak in amplitude at K∗ ≈ 1.5 × 10−3 that is referred to as mode I, and the second that occurs at low values of K∗ (K∗ < 3 × 10−5) that is referred to as mode II. The fluctuating lift is found to be minimum for the mode I oscillation. The mean drag is also found to reach a broad minimum that starts at K∗ corresponding to mode I and continues to be at the same low level of approximately 65% of the bare cylinder drag for all higher K∗ values, representing an approximately 35% decrease in mean drag of the cylinder. The wake measurements also show significant changes with K∗. The formation length (lf /D) obtained from the closure point of the mean separation bubble is found to continuously increase with K∗, reaching values of approximately 2.6 at mode I and thereafter only small increases are seen as K∗ is increased to large values corresponding to the rigid splitter plate case, consistent with the observed variations in the mean drag. The stream wise and cross-stream turbulent intensities and the Reynolds shear stress are all found to be strikingly lower in the mode I case compared to the bare cylinder case, and more importantly, these values are even lower than the rigid splitter plate case. This is consistent with the shedding of weaker vortices and with the minimum in fluctuating lift found in the mode I case. The results for this flap length show that the mode I flap oscillation, corresponding to K∗ ≈ 1.5 × 10−3, may be useful to reduce lift, drag, velocity fluctuations in the wake and the strength of the shed vortices. In particular, the wake fluctuations corresponding to this mode are found to be significantly lower than the rigid splitter plate case. In the short flap case (L/D = 2), it is found that there exists a richer set of flapping modes compared to the long flap, with these modes being dependent on K∗. At low K∗ values, the flap exhibits large amplitude symmetric flap motion that is referred to as mode A, while clearly asymmetric flaps motion are seen at higher K∗ values corresponding to modes B and C. Mode B corresponds to asymmetric large amplitude flapping motion, while mode C is also asymmetric with the flap clearly deflected off to one side, but having small oscillation amplitudes. At even higher K∗ values, corresponding to mode D, symmetric flaps motion are again seen with the amplitudes being smaller than in mode A. Apart from the flap tip amplitude, the non-dimensional frequency of flap tip motion also changes as the flap changes modes. In this case, there is a minimum in the fluctuating lift corresponding to mode B and C oscillation. The mean drag is found to reach a minimum again corresponding to mode C, which corresponds to an approximately 35% decrease in mean drag of the cylinder. In this case, there is a large increase in fluctuating lift (approximately 150% of the bare cylinder case) at higher values of K∗ that appears to correspond to a “resonant” condition between the structural natural frequency of the flexible splitter plate/flap and the wake shedding frequency of the bare cylinder. The wake measurements show that the formation length (lf /D) is the largest for mode C (deflected flap state), which is consistent with the observed minimum in mean drag observed for this mode. The stream wise and cross-stream turbulent intensities and the Reynolds shear stress are all found to be strikingly lower in the mode C case compared to the bare cylinder case, with the values for the Reynolds shear stress being lower than the rigid splitter plate case. This is again consistent with the minimum in fluctuating lift found in the mode C case. The results for this flap length show that the mode C flap oscillation, corresponding to K∗ ≈ 5 × 10−2 that correspond to a deflected flap state with very small oscillation may be useful to reduce lift, drag, velocity fluctuations in the wake and the strength of the shed vortices. The results from the present study show that the flexible flap/splitter plate down-stream of the cylinder exhibits a variety of mode shapes depending on the effective bending rigidity of the flap K∗ for both the long and short flaps cases. The forces and the wake are also found to be strongly dependent on this parameter K∗ with the wake fluctuations, lift fluctuations and the drag being very effectively suppressed at an intermediate value of K∗ that is found to be dependent on the plate/flap length.

The aim of this thesis is to formulate the design of optical access network in designated area. The design is focused on the physical network layer and it covers optical fibers, cable protectors and links, optical hubs, racks and active components. The thesis also docu- ments network architecture, the configuration of active components and provides results from monitoring of selected network segments. The thesis consists of the theoretical part and practical part. In the theoretical part, there is an introduction to optical networks, their configurations (FTTH, FTTB, FTTC, FTTN), relevant networking standards and technologies. The practical part of the thesis covers design proposal of a network located in Slavičín. The design reuses infrastructure and technologies of existing network. The proposed design follows FTTH architecture which has benefits of low maintenance cost and it also fulfills GPON standard.

Čerpadla s nízkými specifickými otáčkami nacházejí uplatnění v široké škále aplikací, ale trpí nízkou účinností a rizikem nestability křivky dopravní výšky. Tato disertační práce pojednává o vylepšení hydraulických parametrů čerpadla se specifickými otáčkami ns = 32. Práce se zaměřuje na průtok v oběžném kole a ve spirále, které jsou řešeny pomocí CFD. Průzkum literatury ukázal, že přidání mezilopatek do průtokového kanálu je účinný způsob, jak zlepšit neuspokojivé proudění obecně přítomné v oběžných kolech s nízkými specifickými otáčkami. Byla zkoumána poloha mezilopatky v kanálu a vliv počtu přítomných mezilopatek. Část výsledků je ověřena experimentálně v laboratoři fakulty. Rovněž je zkoumán tvar spirály a pozornost je věnována numerickému řešení proudění u stěn a jeho vlivu na simulaci. Po numerických výpočtech na třech různých spirálách je navržen nový tvar, který zlepšuje vypočtové parametry čerpadla při nízkém i vysokém průtoku.

There has been a huge surge in data traffic all over the world due to the rise of streamingmedia services and connected devices. The current demand in data traffic has alreadypushed the optical fiber in the internet architecture to the network edges and the trend isto push it as close as possible, to the CPU. Silicon photonics addresses this challenge byenabling miniaturized optical devices that use light to move huge amounts of data at veryhigh speeds with extremely low power. To further improve the data transmission capacity,one can make use of different polarizations of light. However, to take advantage ofdifferent polarizations, devices with on-chip polarization rotation capability are required.This is achieved by a tunable polarization rotator. Moreover, full control of polarizationrotation can also be utilized to realize a new class of components in integrated photonicsincluding polarization mode modulators, multiplexers, filters, as well as switches foradvanced optical signal processing, coherent communications, and sensing.This thesis introduces a novel tunable polarization rotator that uses microelectromechanicalsystems (MEMS) as its actuation principle. When voltage is applied to a MEMStunable silicon cantilever, a mechanical movement occurs, which in turn affects theoptical mode shape travelling through a waveguide, as a result of which the polarizationis rotated. In this work, a MEMS tunable polarization rotator is designed, fabricated,and characterized with a polarization extinction ratio of 10 dB, which works in 1530nm -1570nm wavelength spectrum. In addition to the MEMS tunable polarization rotator,in this thesis, a free standing polarization beam splitter of length 1.4 μm, the shortestreported to-date to our knowledge, was designed, fabricated, and characterized. Thetunable polarization rotator and beam splitter developed in this thesis have the potentialto increase the bandwidth and flexibility of current optical communication networks, andfind further applications in polarization diversity schemes for sensing. / Mängden datatrafik i världen har växt explosionsartat de senaste åren på grund av detökade antalet uppkopplade enheter samt det snabbt växande tjänsterna för strömmad media. Det stora databehovet har redan gjort det nödvändigt att använda högkapacitiva optiska länkar hela vägen till nätverkets kanter och trenden är att optisk dataöverföring används närmare och närmare själva CPU:erna i datorerna som utgör källa och slutpunkt för all data på Internet. Kiselfotonik möter denna utmaning genom att möjliggöra miniatyriserade optiska system som använder ljus för att snabbt överföra stora mängder data med liten effektförbrukning. För att öka kapaciteten ännu mer kan man använda sig av ljusets polarisation. För att göra detta måste man tillhandahålla system för att vrida polarisation på chipp-nivå vilket man kan åstadkomma med en avstämbar polarisationsvridare. Utöver en ökad kapacitet kan den nya kontrollen över polarisation även användas för att skapa nya typer av integrerade optiska komponenter som polarisationsbaserade modulatorer, multiplexers, filter, såväl som switchar för optisk signalbehandling, koherent kommunikation och avkänning.Denna avhandling presenterar en ny avstämbar polarisationsvridare som använder en mikroelektromekanisk (MEMS) aktuator. När en spänning är applicerad på en MEMS balk skapas en mekanisk rörelse som i sin tur påverkar den optiska mod-bilden som propagerar i en integrerad optisk vågledare vilket resulterar i att polarisationen vrids. Denna avhandling innehåller design, tillverkning och karakterisering av en avstämbar polarisationsvridare med en polariseringsgrad på 10 dB i våglängdsområdet 1530-1570 nm. Utöver det presenteras design, tillverkning och karakterisering av frihängande polarisationsfördelare med en längd på endast 1.4 µm, den kortaste hittills rapporterad. Dessa komponenter har potentialen att öka bandbredden och flexibilite befintligaoptiska kommunikationsnät och hitta nya tillämpningar i sensorsystem.

Optical interconnects based on CMOS compatible photonic integrated circuits are regarded as a promising technique to tackle the issues traditional electronics faces, such as limited bandwidth, latency, vast energy consumption and so on. In recent years, plasmonic integrated components have gained great attentions due to the properties of nano-scale confinement, which may potentially bridge the size mismatch between photonic and electronic circuits. Based on silicon nanowire platform, this thesis work studies the design, fabrication and characterization of several integrated plasmonic components, aiming to combine the benefits of Si and plasmonics. The basic theories of surface plasmon polaritons are introduced in the beginning, where we explain the physics behind the diffraction-free confinement. Numerical methods frequently used in the thesis including finite-difference time-domain method and finite-element method are then reviewed. We summarize the device fabrication techniques such as film depositions, e-beam lithography and inductively coupled plasma etching as well as characterization methods, such as direct measurement method, butt coupling, grating coupling etc. Fabrication results of an optically tunable silicon-on-insulator microdisk and III-V cavities in applications as light sources for future nanophotonics interconnects are briefly discussed. Afterwards we present in details the experimental demonstrations and novel design of plasmonic components. Hybrid plasmonic waveguides and directional couplers with various splitting ratios are firstly experimentally demonstrated. The coupling length of two 170 nm wide waveguides with a separation of 140 nm is only 1.55 µm. Secondly, an ultracompact polarization beam splitter with a footprint of 2×5.1 μm2 is proposed. The device features an extinction ratio of 12 dB and an insertion loss below 1.5 dB in the entire C-band. Thirdly, we show that plasmonics offer decreased bending losses and enhanced Purcell factor for submicron bends. Novel hybrid plasmonic disk, ring and donut resonators with radii of ~ 0.5 μm and 1 μm are experimentally demonstrated for the first time. The Q-factor of disks with 0.5 μm radii are                         , corresponding to Purcell factors of . Thermal tuning is also presented. Fourthly, we propose a design of electro-optic polymer modulator based on plasmonic microring. The figure of merit characterizing modulation efficiency is 6 times better comparing with corresponding silicon slot polymer modulator. The device exhibits an insertion loss below 1 dB and a power consumption of 5 fJ/bit at 100 GHz. At last, we propose a tightly-confined waveguide and show that the radius of disk resonators based on the proposed waveguide can be shrunk below 60 nm, which may be used to pursue a strong light-matter interaction. The presented here novel components confirm that hybrid plasmonic structures can play an important role in future inter- and intra-core computer communication systems. / <p>QC 20140404</p>

The main subject of this diploma thesis is to make a proposal to improve the optical access network for the transmission of Triple play services. I would here to the reader clarify method of proposal of optical network. There are described the kinds of optical access networks with parameters, for which we must look by their construction. There are described the modern methods of construction optical network too. In the theoretical part are discussed used architecture of networks too. I met here known standards, which I compared for big importance by their choice. A reason of construction of optical network are services known like Triple play. These services together with their problems and parameters are here discussed too. At the end of theoretical part I listed here measuring method for getting negative attribute distorting the led signal. In practical part the locality witch use the optical signal as the source of information is ordered. These network use unfit connections and has less possibilities than usual and this is the reason, why is the network not able to supply Triple play in requested quality. At first the analysis of ordered network was needed. Situation was complicated by the fact, that it has been prohibited entrance to me. The structure of network and network parts was known and documented by me. I made the proposals to improve this network in practical part. By the first proposal remained original kind of access network FTTB, but used new parts with higher performance. By the second proposal I made the network FTTH, by which it was possible to use the last haul optical cables with treatment and using new elements. It was needed to create solution by flat units. The resulting proposals are here evaluated, compared and cost evaluated. For rejection of access to optical network I did not make measuring, so I made simulation for variant FTTH for getting some parameters negative acting transmission.

Optical devices based on planar lightwave circuit (PLC) technology have the advantages of small size, high reliability, possibility for large scale production, and potential integration with electronics. These devices are widely employed in optical telecommunications, sensing, data storage, imaging, and signal processing. This thesis focuses on some selected PLC based devices, such as power splitters, demultiplexers, triplexers and polarization beam splitters. First, the basic principle of the waveguides and the simulation methods for PLC devices are discussed. A novel effective index method is introduced to reduce a two-dimensional structure to a one-dimensional one, and can be implemented for arbitrarily shaped waveguides. Numerical methods, such as finite-difference mode solver, beam propagation method, finite-difference time-domain method are introduced to analysis the mode profile of the waveguides, and the propagation properties of light in PLC devices. Multimode interference (MMI) couplers are widely used in many PLCs, such as power splitters, ring lasers, optical switches, and wavelength division multiplexers/demultiplexers. In this work, concepts for improving the self-imaging quality of MMI couplers are analyzed and new designs are proposed. A significant improvement in performance together with compact sizes were obtained with taper sections at the input/output of MMI couplers based on SOI, and deeply etched ridges in MMI couplers based on SiO2. A polarization insensitive dual wavelength demultiplexer based on sandwiched MMI waveguides was presented. Novel devices including triplexers and polarization beam splitters were realized by using photonic crystal (PhC) structures. Two stages of directional couplers based on PhC waveguides are cascaded to form an ultracompact triplexer. The special decoupling property of the PhC waveguide based directional coupler was utilized in the design. A novel polarization beam splitter was realized by combining a MMI coupler and a PhC which works as a polarization sensitive reflector. Finally, fabrication and optical characterization of an ultra-compact directional coupler and PhC structures in InP are presented. In a single etching step, by using the lag-effect in inductively coupled plasma reactive ion etching, a compact directional coupler (55 μm) is demonstrated. Carrier life times in PhC structures etched by chemically assisted ion beam etching were investigated, for emitter and switching applications. / QC 20100909

The flow around a finite square prism has not been studied extensively when compared with an “infinite” (or two-dimensional) square prism. In the present study, the effect of a wake-mounted splitter plate on the flow around a surface-mounted square prism of finite height was investigated experimentally using a low-speed wind tunnel. Of specific interest were the combined effects of the splitter plate length and the prism’s aspect ratio on the vortex shedding, mean drag force coefficient, and the mean wake. Four square prisms of aspect ratios AR = 9, 7, 5 and 3 were tested at a Reynolds number of Re = 7.4×104 and a boundary layer thickness of /D = 1.5. Splitter plate lengths of L/D = 1, 1.5, 2, 3, 5, and 7, were tested, with all plates having the same height as the prism. Measurements of the mean drag force were obtained with a force balance, and measurements of the vortex shedding frequency were obtained with a single-component hot-wire probe. A seven-hole pressure probe was used to measure the time-averaged wake velocity at a Reynolds number of Re = 3.7×104 for AR = 9 and 5 with splitter plates of lengths L/D = 1, 3, 5, and 7. These measurements were carried out to allow for a better understanding of how the splitter plate affects the mean wake of the finite prism. The results show that the splitter plate is a less effective drag-reduction, but more effective vortex-shedding-suppression, device for finite square prisms than it is for infinite square prisms. Significant reduction in the mean drag coefficient was realized only for short prisms (of AR ≤ 5) when long splitter plates (of L/D ≥ 5) were used. A splitter plate of length L/D = 3 was able to suppress vortex shedding for all aspect ratios tested. However, for square prisms of aspect ratios AR ≤ 7, the splitter plate is a less effective vortex-shedding-suppression device when compared to its use with finite circular cylinders, i.e. longer splitter plates are needed for vortex shedding suppression with square prisms. Wake measurements showed distinct wake velocity fields for the two prisms tested. For the prism of AR = 9, a strong downwash flow in the upper part of the wake became weaker towards the ground plane. For the prism of AR = 5, the downwash remained strong close to the ground plane. With splitter plates installed, the downwash became weaker for both prisms. The splitter plate was found to narrow the wake width, especially close to the ground plane, and led to the stretching of the streamwise vortex structures in the vertical direction, and increased entrainment towards the wake centreline in the cross-stream direction.

En algorithmique distribuée, le modèle asynchrone par envoi de messages et à pannes est connu et utilisé dans de nombreux articles de par son réalisme,par ailleurs il est suffisamment simple pour être utilisé et suffisamment complexe pour représenter des problèmes réels. Dans ce modèle, les n processus communiquent en s'échangeant des messages, mais sans borne sur les délais de communication, c'est-à-dire qu'un message peut mettre un temps arbitrairement long à atteindre sa destination. De plus, jusqu'à f processus peuvent tomber en panne, et ainsi arrêter définitivement de fonctionner. Ces pannes indétectables à cause de l'asynchronisme du système limitent les possibilités de ce modèle. Dans de nombreux cas, les résultats connus dans ces systèmes sont limités à une stricte minorité de pannes. C'est par exemple le cas de l'implémentation de registres atomiques et de la résolution du renommage. Cette barrière de la majorité de pannes, expliquée par le théorème CAP, s'applique à de nombreux problèmes, et fait que le modèle asynchrone par envoi de messages avec une majorité de pannes est peu étudié. Il est donc intéressant d'étudier ce qu'il est possible de faire dans ce cadre.Cette thèse cherche donc à mieux comprendre ce modèle à majorité de pannes, au travers de deux principaux problèmes. Dans un premier temps, on étudie l'implémentation d'objets partagés similaires aux registres habituels, en définissant les bancs de registres x-colorés et les α-registres. Dans un second temps, le problème du renommage est étendu en renommage k-redondant, dans ses versions à-un-coup et réutilisable, et de même pour les objets partagés diviseurs, étendus en k-diviseurs. / In distributed computing, asynchronous message-passing model with crashes is well-known and considered in many articles, because of its realism and it issimple enough to be used and complex enough to represent many real problems.In this model, n processes communicate by exchanging messages, but withoutany bound on communication delays, i.e. a message may take an arbitrarilylong time to reach its destination. Moreover, up to f among the n processesmay crash, and thus definitely stop working. Those crashes are undetectablebecause of the system asynchronism, and restrict the potential results in thismodel.In many cases, known results in those systems must verify the propertyof a strict minority of crashes. For example, this applies to implementationof atomic registers and solving of renaming. This barrier of a majority ofcrashes, explained by the CAP theorem, restricts numerous problems, and theasynchronous message-passing model with a majority of crashes is thus notwell-studied and rather unknown. Hence, studying what can be done in thiscase of a majority of crashes is interesting.This thesis tries to analyse this model, through two main problems. The first part studies the implementation of shared objects, similar to usual registers,by defining x-colored register banks, and α-registers. The second partextends the renaming problem into k-redundant renaming, for both one-shotand long-lived versions, and similarly for the shared objects called splitters intok-splitters.

L'essor des télécommunications sur fibres a conduit depuis quarante ans au développement des composants optiques intégrés. Cependant, en raison de difficultés technologiques, un dispositif n'a pas encore été réalisé de façon satisfaisante : il s'agit de l'isolateur optique, dont la fonction est de propager la lumière dans un seul sens. Ces travaux s'inscrivent dans cette problématique puisqu'ils visent à l'intégration d'un isolateur grâce à la technologie de l'échange d'ions Na+/Ag+ sur verre. La configuration adoptée se compose de trois éléments sur puce : un séparateur de polarisation et deux rotateurs de polarisation à 45 °, l'un réciproque et l'autre non. Le séparateur de polarisation a été réalisé sous la forme d'une jonction Y asymétrique. Après une étude théorique, nous présentons le procédé de fabrication ainsi que les résultats expérimentaux obtenus. Les diaphonies mesurées sont à l'état de l'art, elles dépassent (31,1 ± 0,4) dB et (32,7 ± 0,4) dB en mode TE et TM sur une plage spectrale supérieure à 70 nm. Nous avons mené l'étude du rotateur Faraday en collaboration avec le Laboratoire Télécom Claude Chappe de Saint Etienne pour la partie magnéto-optique. La structure employée est un guide d'onde à enterrage différentiel sur lequel est déposé un matériau magnéto-optique par un procédé sol-gel. Un angle de rotation non-réciproque de 50 ° a été mesuré, validant ainsi l'approche hybride. Un nouveau procédé de fabrication est également présenté pour un rotateur réciproque à évolution de mode adiabatique. Celui-ci consiste en un enterrage sous champ présentant une inhomogénéité transverse. Nous proposons finalement une méthode de fabrication de l'isolateur complet basée sur l'intégration monolithique des différents éléments. / For the past forty years, the growth of fiber telecommunications has led to the development of integrated optical components. However, due to technological issues, a device has not yet been realized: the optical isolator, which propagates light in a single direction. Our work fits into this context. It deals with the integration of an isolator using the Na+/Ag+ ion-exchange technology. The configuration we adopted consists of three elements on chip: a polarization splitter and two 45 ° polarization rotators, one is reciprocal and the other is not. The polarization splitter has been realized in the shape of an asymmetrical Y junction. After a theoretical study, we present the fabrication process and experimental results. State-of-the-art diaphonies of (31.1 ± 0.4) dB and (32.7 ± 0.4) dB have been measured in TE and TM mode over a bandwidth larger than 70 nm. The magneto-optical part of the study has been undertaken in collaboration with the Laboratoire Télécom Claude Chappe (LT2C) from Saint Etienne, France. The Faraday rotator is a selectively buried waveguide on which a magneto-optical material has been deposited using a sol-gel process. A non-reciprocal rotation of 50 ° has been measured, hence validating the hybrid approach. A novel fabrication process is presented for a reciprocal mode-evolution polarization rotator. The process consists in the burring of a waveguide under an electric field presenting a transverse inhomogeneity. We finally propose a fabrication method of the complete optical isolator. It is based on the monolithic integration of the three elements.