Single wall carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) were dispersed in mineral oil and epoxy resin. The magnetorheological properties of these dispersions were studied using a parallel plate rheometer. Strain sweeps, frequency sweeps, magneto sweeps and steady shear tests were conducted in various magnetic fields. G', G", h* and ty increased with increasing magnetic field, which was partially attributed to the increasing degree of the alignment of nanotubes in a stronger magnetic field. The SWNT/mo dispersions exhibited more pronounced magnetic field dependence than SWNT/ep and MWNT/mo counterparts due to their much lower viscosity. The alignment of SWNTs in mineral oil increased with rising nanotube concentration up to 2.5vol% but were significantly restricted at 6.41vol% due to nanotube flocculation.

Durch die wachsende Bedeutung der DNS-Sequenzierung wurden die Geräte zur Sequenzierung weiterentwickelt und ihr Durchsatz so erhöht, dass sie Millionen kurzer Nukleotidsequenzen innerhalb weniger Tage liefern. Moderne Algorithmen und Programme, welche die dadurch entstehenden großen Datenmengen in akzeptabler Zeit verarbeiten können, ermitteln jedoch nur einen Bruchteil der Positionen der Sequenzen in bekannten Datenbanken. Eine derartige Suche ist eine der wichtigsten Aufgaben in der modernen Molekularbiologie. Diese Arbeit untersucht mögliche Übertragungen moderner Genom-Alignment Programme auf hochparallele Plattformen wie FPGA und GPU. Die derzeitig an das Problem angepassten Programme und Algorithmen werden untersucht und hinsichtlich ihrer Parallelisierbarkeit auf den beiden Plattformen FPGA und GPU analysiert. Nach einer Bewertung der Alternativen erfolgt die Auswahl eines Algorithmus. Anschließend wird dessen Übertragung auf die beiden Plattformen entworfen und implementiert. Dabei stehen die Geschwindigkeit der Suche, die Anzahl der ermittelten Positionen sowie die Nutzbarkeit im Vordergrund. Der auf der GPU implementierte reduzierte Smith & Waterman-Algorithmus ist effizient an die Problemstellung angepasst und erreicht für kurze Sequenzen höhere Geschwindigkeiten als bisherige Realisierungen auf Grafikkarten. Eine vergleichbare Umsetzung auf dem FPGA benötigt eine deutlich geringere Laufzeit, findet ebenfalls jede Position in der Datenbank und erreicht dabei ähnliche Geschwindigkeiten wie moderne leistungsfähige Programme, die aber heuristisch arbeiten. Die Anzahl der gefundenen Positionen ist bei FPGA und GPU damit mehr als doppelt so hoch wie bei sämtlichen vergleichbaren Programmen. / Further developments of DNA sequencing devices produce millions of short nucleotide sequences. Finding the positions of these sequences in databases of known sequences is an important problem in modern molecular biology. Current heuristic algorithms and programs only find a small fraction of these positions. In this thesis genome alignment algorithms are implemented on massively parallel platforms as FPGA and GPU. The next generation sequencing technologies that are currently in use are reviewed regarding their possible parallelization on FPGA and GPU. After evaluation one algorithm is chosen for parallelization. Its implementation on both platforms is designed and realized. Runtime, accuracy as well as usability are important features of the implementation. The reduced Smith & Waterman algorithm which is realized on the GPU outperforms similar GPU programs in speed and efficiency for short sequences. The runtime of the FPGA approach is similar to those of widely used heuristic software mappers and much lower than on the GPU. Furthermore the FPGA guarantees to find all alignment positions of a sequence in the database, which is more than twice the number that is found by comparable software algorithms.

<p>Millimeter-wave communications use narrow beams to overcome the enormous signal attenuation. Such narrow-beam communication demands precise beam-alignment between transmitter and receiver and may entail huge overhead, especially in high mobility scenarios. Moreover, detection of the optimal beam is challenging in the presence of beam imperfections and system noise. This thesis addresses the challenges in the design of beam-training and data-communication by proposing various schemes that exploit different timescales. On a short timescale, we leverage the feedback from the receiver to efficiently perform beam-training and data-communication. To this end, we have worked in three different areas. In the first research direction, we design an optimal interactive beam-training and data-communication protocol, with the goal of minimizing power consumption under a minimum rate constraint. The optimality of a fixed-length beam-training phase followed by a data-communication phase is proved under the assumption of perfect binary feedback. In the second research direction, we propose a coded energy-efficient beam-training scheme, robust against the feedback/detection errors. In the third research direction, we investigate the design of the beam-training in the presence of uncertainty due to noise and beam imperfections. Based on the bounding of value-function, the second-best preference policy is proposed, which achieves a promising exploration-exploitation tradeoff. On the other hand, on longer timescales, we exploit the mobility and blockage dynamics and beam-training feedback to design throughput-efficient beam-training and data-communication. We propose a point-based value iteration (PBVI) algorithm to determine an approximately optimal policy. However, the design relies on the a-priori knowledge of the state dynamics, which may not be available in practice. To address this, we propose a dual timescale approach, where on the long timescale, a recurrent deep variational autoencoder (R-VAE) uses noisy beam-training observations to learna probabilistic model of system dynamics; on the short timescale, an adaptive beam-training procedure is optimized using PBVI based on beam-training feedback and a probabilistic knowledge of the UE's position provided by the R-VAE. In turn, the observations collected during the beam-training procedure are used to refine the R-VAE via stochastic gradient descent in a continuous process of learning and adaptation.<br></p>

Optical wireless communication (OWC) offers many benefits over established radio frequency–based communication links. Particularly in, high-data services, high security, and license-free operation, OWC link are becoming an attractive solution for the next generation of communication systems. In OWC, precise alignment of the incoming beam is necessary to close the communication link. However, precisely aligning the beam between the transceivers is challenging due to the laser beam’s narrowness and external disturbances that can significantly reduce, destroy, or scatter the beam signal. Therefore, designing optimized control strategies can significantly improve the alignment precision, which is the main motivation for this work. This thesis deploys standard and optimal control techniques, with an emphasis on optimized control strategies, to address the alignment problem in underwater optical wireless communication (UOWC) and in laser beam stabilizer systems within a vibrating environment. First, the UOWC system’s alignment problem was investigated in a vibrating scenario. For its effective control, the properties of light propagation were considered by accounting for the dynamical model that describes the propagation characteristics of the signal beam between transceivers. To control the UOWC system, we designed an observer-based optimal controller approach that combined the unconstrained and constrained optimal controllers, namely linear quadratic regulator (LQR) and model predictive control (MPC) with the extended Kalman filter (EKF). The latter enabled estimations of the beam dynamics from the power of the received beam signal. Extensive simulation tests were conducted that demonstrated the efficiency of the MPC algorithm compared to the LQR, fractional order proportional integral derivative (FOPID) and conventional PID controllers in terms of tracking and robustness against the disturbance levels. Second, the alignment problem in the laser beam stabilizer system was considered, whereby the designed control algorithms were tested experimentally in a vibrating disturbance. For this particular system, the LQR and MPC optimal controllers were designed both in simulation and experimental environments. The designed optimal control algorithms were compared to a conventional PID controller and its optimized variants (e.g., fractional and robust), demonstrating the MPC design’s outperformance in terms of tracking error and robustness to different voltage disturbance levels.

III-nitride semiconductors have garnered significant attention due to their diverse applications in the fields of optics and electronics. As GaN-based visible light-emitting diodes (LEDs) and laser technologies continue to advance, there has been a surge of interest in the development of ultraviolet (UV) devices. In order to explore the UV range, extensive research has been conducted on BN-based materials and their alloys with conventional III-nitrides, driven by the quest for materials exhibiting larger bandgaps and enhanced refractive index contrast. Additionally, the incorporation of boron into III-nitrides through alloying provides a promising avenue for effectively modulating lattice parameters and manipulating the crystalline structure. This offers a novel approach for strain engineering, lattice matching, and structural manipulation, facilitating the optimization of device performance and expanding the capabilities of III-nitride semiconductors in the realm of UV device development. In this work, we optimize and investigate the epitaxial growth of BGaN using metalorganic chemical vapor deposition, and characterize the physical and electronic properties of the grown films using several techniques such as X-ray diffraction, atomic force microscopy, UV-Visible spectroscopy, X-ray Photoelectron Spectroscopy (XPS), electron energy loss spectroscopy (EELS) and more. We have explored different metalorganic chemical vapor deposition techniques —such as continuous growth and pulsed-flow modulation, high temperature and low temperature growths, hydrogen-containing and hydrogen-free growths, trimethylgallium (TMG) and triethylgallium (TEG) sourced growths, Triethylborane (TEB) and borazine (BRZN) sourced growths— to grow BGaN alloys. Samples grown using continuous-flow method, low temperatures, TEG source and hydrogen-free carrier gas show higher boron content and better crystalline quality when having TEB as a boron source. BRZN is used to reduce carbon impurities for the purpose of film doping. With BRZN, TMG was found as a preferred gallium source. Additionally, we have characterized the electronic properties of the grown films in details using XPS, EELS and other related techniques. We have studied the band offset of BGaN with AlN using traditional methods. Furthermore, we have developed a statistical technique to find small offsets at interfaces at the precision of the measuring instrument.

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Darwin first proposed sexual selection as a process to explain the evolution of extravagant morphological traits in males. Despite being potentially detrimental to individual survival, such traits evolve because they increase a male's reproductive success, and provide a net benefit to their fitness. Mate competition is the source of sexual selection, and healthier, more vigorous males are likely to be superior competitors. Because most genes are likely to impact an individual’s health/vigour, sexual selection should act across much of the genome to favour the same alleles as natural selection, thereby promoting adaptation. On the other side of the coin, adaptation to an environment should enhance male sexual fitness, since it is likely to increase the overall health/vigour of individuals within a population, though tests of this prediction are rare and results are mixed. Taking advantage of a long-term evolution experiment involving replicate populations of Drosophila melanogaster, I performed a reciprocal transplant in which the sexual fitness of males was compared when raised in an environment to which they are well adapted and in one to which they are not. I improved on past tests via a comprehensive measure of male sexual fitness that included pre- and post-copulatory reproductive success in a competitive assay under conditions that closely mirrored those to which the populations have been evolving. I found that sexual fitness was higher in locally-adapted males from these experimental populations, a result that was consistent across environments that also manipulated the context in which mate competition occurred.

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