In this thesis, we analyze the performance of heterogeneous wireless communication systems that are composed of Optical Wireless Communication (OWC) and Radio Frequency (RF) systems. OWC systems further include long range outdoor Free Space Optical (FSO) systems and short range indoor Visible Light Communication (VLC) systems. Hybrid FSO/RF systems have emerged as a promising solution for high data rate wireless transmissions. Various transmission schemes including switch-over and soft-switching had been presented for hybrid FSO/RF systems. To overcome the drawbacks of existing schemes, we present a new transmission strategy for hybrid FSO/RF systems exploring an adaptive combining technology. This new strategy shows an improved outage performance. Typically, when the transmitter and the receiver are provided with channel state information, the transmission schemes can be adaptively designed allowing the channel to be used more efficiently. We present two new joint adaptive transmission schemes for hybrid FSO/RF systems. The first one is joint adaptive modulation and adaptive combining scheme which improves the spectral efficiency of hybrid FSO/RF systems. The other one is joint power adaptation and adaptive combining scheme which improves the throughput and the outage performance of hybrid FSO/RF systems. We accurately evaluate the performance of both schemes. FSO technology can be used effectively in multiuser scenarios to support Point-to-Multi-Point (P2MP) networks. In P2MP networks, FSO links are used for data transmission from a central location to multiple users. In this thesis, we present a new P2MP network based on hybrid FSO/RF transmission system. A common backup RF link is used by the central station for data transmission to any user in case of the failure of its corresponding FSO link. Based on a Markov Chain formulation, we study the performance of the resulting system. P2MP Hybrid FSO/RF network achieves considerable performance improvement over the P2MP FSO-only network. In VLC, Light Emitting Diode (LED) is used for the purpose of simultaneous illumination and data communication at high data rate. However, the light originating from a LED source is naturally confined to a small area and is susceptible to blockages. Hybrid VLC/RF systems have been emerged as a promising solution to provide enhanced communication coverage. We introduce a new dual-hop VLC/RF system with energy harvesting relay to extend the coverage of indoor wireless system based on VLC. The second-hop RF transmission uses the harvested energy over the first-hop VLC transmission. In this thesis, we propose two different approaches for energy harvesting at the relay terminal. In the first approach, the relay harvests light energy from different artificial light sources and sunlight entering the room. In this approach, we propose a novel statistical model for the harvested electrical power and analyze the probability of data packet loss. In the second approach, the relay harvests energy from the VLC link by extracting the direct current component of the received optical signal. In this approach, we investigate the optimal design of the hybrid VLC/RF system in terms of data rate maximization. In both cases, we present extensive numerical examples to define important design guide lines for VLC/RF systems. / Graduate

Stricter regulations and evolving environmental concerns have been exerting ever-increasing pressure on the automotive industry to produce low carbon vehicles that reduce emissions. As a result, increasing numbers of alternative powertrain architectures have been released into the marketplace to address this need. However, with a myriad of possible alternative powertrain configurations, which is the most appropriate type for a given vehicle class and duty cycle? To that end, comparative analyses of powertrain configurations have been widely carried out in literature; though such analyses only considered limited types of powertrain architectures at a time. Collating the results from these literature often produced findings that were discontinuous, which made it difficult for drawing conclusions when comparing multiple types of powertrains. The aim of this research is to propose a novel methodology that can be used by practitioners to improve the methods for comparative analyses of different types of powertrain architectures. Contrary to what has been done so far, the proposed methodology combines an optimisation algorithm with a Modular Powertrain Structure that facilitates the simultaneous approach to optimising multiple types of powertrain architectures. The contribution to science is two-folds; presenting a methodology to simultaneously select a powertrain architecture and optimise its component sizes for a given cost function, and demonstrating the use of multi-objective optimisation for identifying trade-offs between cost functions by powertrain architecture selection. Based on the results, the sizing of the powertrain components were influenced by the power and energy requirements of the drivecycle, whereas the powertrain architecture selection was mainly driven by the autonomy range requirements, vehicle mass constraints, CO2 emissions, and powertrain costs. For multi-objective optimisation, the creation of a 3-dimentional Pareto front showed multiple solution points for the different powertrain architectures, which was inherent from the ability of the methodology to concurrently evaluate those architectures. A diverging trend was observed on this front with the increase in the autonomy range, driven primarily by variation in powertrain cost per kilometre. Additionally, there appeared to be a trade-off in terms of electric powertrain sizing between CO2 emissions and lowest mass. This was more evident at lower autonomy ranges, where the battery efficiency was a deciding factor for CO2 emissions. The results have demonstrated the contribution of the proposed methodology in the area of multi-objective powertrain architecture optimisation, thus addressing the aims of this research.

Georgia Tech has the privilege of competing in EcoCAR 3, a four-year competition in which 16 universities are given a stock 2016 Chevrolet Camaro and work to transform it into a hybrid electric sports car. In this thesis, an overview of the first two years of the author’s work on the team as the Engineering Manager, the graduate student overseeing all vehicle engineering work, will be detailed. The competition will be introduced and described before a discussion on vehicle electrification and the various ways it has been achieved by manufacturers and competition teams. Next, the design of the Georgia Tech vehicle will be presented with a focus on powertrain and supporting component selection. The vehicle model underlying many of these decisions will then be discussed in detail, showing how the team used Simulink and Engineering Equation Solver to effectively predict vehicle performance, emissions, energy consumption, and cooling needs. Building on this, the controls design process known as model/software/hardware in the loop will be discussed in the context of the Georgia Tech team’s use of this process. Finally, a progress update will be given, including photos of the team vehicle in current build state weeks before the Year 2 Competition.

Finding cleaner and sustainable energy resources is one of the most important concerns for the development of humanity. Solar energy is taking an essential role in this matter as the production cost of solar collectors is decreasing and more solar installations are being set up every year throughout the world. One way of reducing the cost of solar panels is by using concentrators that are cheaper than the costly photovoltaic cells and can increase their output. Solarus AB designed a Photovoltaic Thermal (PVT) hybrid collector that uses this principle and which is a variation of the Maximum Reflector Collector (MaReCo) design and is a Compound Parabolic Collector (CPC). This thesis has two main objectives. The first one is to design variations of the actual Solarus’ design and some alternative MaReCo designs and pure parabola designs. These designs include new solar cell cuts which are based on 4 busbar solar cells. In this way a future in-depth analysis may be carried out by comparing different receiver designs and collector boxes. The second goal is to investigate the current electrical and thermal performance of the collectors from Solarus AB which are installed in the Hus 45 of HiG. The appropriate data of the installation has been obtained using simulations and specific software, and it has been analysed with Microsoft Excel®. Concerning the new designs of the receivers and boxes, everything has been prepared for the future construction of the prototypes. All the measurements and their adjustments have been taken into account to define the size of the components and the process of building has been set up. Moreover, some future work has been planned in order to move forward the project. Regarding the analysis of the HiG installation, both electrical and thermal performance have resulted to be significantly lower compared with their estimated simulation, being their real output around 60 % of the estimated one. In the thermal part, the losses in the pipeline result to be more than a third part of the produced heat. In the electrical part, the production varies a lot between different collectors due to some of them do not work properly, consequence of poor condition of the solar panels (broken cells, dirt, shading, etc.).

The paper describes the design of a prototype vehicle used by Dana Holding Corporation as a mobile laboratory for the development of Spicer® PowerBoost® hydraulic-hybrid powertrain technology. A telehandler vehicle was selected due to its versatility. Starting from the high-level requirements, design choices from the powertrain layout to the control architecture are discussed. The hydraulic-hybrid powertrain system is described, and its performance is analyzed based on representative driving cycles.

During the past three years the Institute for Fluid Power Drives and Controls in Aachen has developed a new hydraulic system for mobile machinery called STEAM. The system represents a new step in excavator hydraulics, as it aims to reduce both the hydraulic system losses as well as those of the internal combustion engine by using a hybrid hydraulic architecture with accumulators. Starting with initial simulation studies the development has been followed by scaled test bench measurements and has progressed to a full scale validation using an 18 t excavator. The following publication aims to summarise the results obtained thus far with the aim of making them available to industry and encouraging their implementation in future applications.

Motivated by the lack of scholarship surrounding female characters in Gabriel Garcia Marquez's One Hundred Years of Solitude, I sought to examine the distinct identities of four female characters. The collapse of dualities and embodiment of hybridity in Ursula, Pilar Ternera, Amaranta, and the Remedios women reveals the hegemonic power structures that are disrupted by these empowered women. The exploration of these women and their relationships to gendered dichotomies points to the potential of their identities in enacting colonial resistance and reclaiming traditional cultural heritage.

Many technical hurdles remain to be overcome before an advanced fuel cycle in which minor actinides from spent nuclear fuel are used to generate power. Three such issues were addressed: criticality safety of minor actinides as compared to currently used fissile isotopes; accuracy of evaluated nuclear data for selected minor actinide high energy fission cross-sections; and the preliminary design optimization of a minor actinide burning/breeding fission blanket in a fission fusion hybrid reactor concept. For minor actinide compositions found in spent fuel, current safety measures for actinide solutions were found to be adequate, though concerns may remain for unmoderated transuranic materials. Additionally, computational results indicated a 5-10% error in the fission cross-section of some minor actinides above the fast fission threshold. Finally, a relatively tall annular fission blanket was found to be the most ideal configuration for the UT fission- fusion hybrid reactor concept, satisfying criticality and power output criteria. / text

This thesis is devoted to the analysis of problems that arise when long products of matrices taken in a given set are constructed. A typical application is the stability of switched linear systems. The stability of a discrete-time linear system is a classical engineering problem that has been well understood for long: the dynamics can be expressed in terms of the eigenvalues of the matrix ruling the system. A more complicated problem arises when the dynamical system can switch, that is, if the matrix changes over time. If this matrix is taken from a given set but can be chosen arbitrarily in this set at every time, the stability problem turns to the computation of a quantity, the joint spectral radius of the set of matrices, introduced in the early sixties. While this quantity appears to be hard to compute, it has acquired more and more importance during the last decades, and new applications of the joint spectral radius in engineering or mathematics are frequently discovered. It has for instance been proved useful for the analysis of regularity of fractals, for the continuity of wavelets, or for autonomous agents detection in sensor networks. In the first part of this thesis, we present a theoretical survey of the joint spectral radius, including old and new results. The joint spectral subradius, which is its stabilizability counterpart, is also considered. In a second part, we study some applications related to long products of matrices. We first analyse in detail a problem in coding theory, that has been recently shown to involve a joint spectral radius computation. We then propose a new application of the joint spectral radius (and related quantities) to a classical problem in number theory, namely the counting of overlap-free words. We then turn to problems related with autonomous agents detection: we analyse the trackability of sensor networks, and introduce and analyse a new notion, namely the observability of sensor networks.

In the field of formal verification of real-time systems, major developments have been recorded in the last fifteen years. It is about logics, automata, process algebra, programming languages, etc. From the beginning, a formalism has played an important role: timed automata and their natural extension,hybrid automata. Those models allow the definition of real-time constraints using real-valued clocks, or more generally analog variables whose evolution is governed by differential equations. They generalize finite automata in that their semantics defines timed words where each symbol is associated with an occurrence timestamp. The decidability and algorithmic analysis of timed and hybrid automata have been intensively studied in the literature. The central result for timed automata is that they are positively decidable. This is not the case for hybrid automata, but semi-algorithmic methods are known when the dynamics is relatively simple, namely a linear relation between the derivatives of the variables. With the increasing complexity of nowadays systems, those models are however limited in their classical semantics, for modelling realistic implementations or dynamical systems. In this thesis, we study the algorithmics of complex semantics for timed and hybrid automata. On the one hand, we propose implementable semantics for timed automata and we study their computational properties: by contrast with other works, we identify a semantics that is implementable and that has decidable properties. On the other hand, we give new algorithmic approaches to the analysis of hybrid automata whose dynamics is given by an affine function of its variables.