Dissertations / Theses on the topic 'Generators'

Three heterocyclic systems were prepared along with derivatives. The thermal decompositions of these heterocycles was examined and their suitability as gas generators assessed, with respect to, melting point, decomposition temperature, volume and type of gases evolved, ease of hydrolysis, and ease of preparation. The preparation of 2-azido-5-phenyl-1,3,4-oxadiazole by a variety of routes is described. It was stable above its melting point and at higher temperatures decomposition was violent, evolving nitrogen, along with the formation of benzoyl cyanide. 1,2,4-Oxadiazolidine-3,5-dione melted at 103-105^oC and decomposed at ca 155^oC with gas evolution. 2,2'-Adipoyldi-1,2,4-oxadiazolidine-3,5-dione and the corresponding succinyl derivatives were prepared in good yield and decomposed on melting. The oxalyl and malonyl derivatives were more difficult to prepare due to their ease of hydrolysis. The oxalyl derivative decomposed ca 20^o above its melting point. Parabanic acid (2,4,5-triketoimidazolidine) was easily prepared in high yield and decomposed on melting. N,N'-Diacetyl- and N,N'-dibenzoyl-parabanic acids were prepared, via the disodium salt of parabanic acid, and decomposed on melting. Monoacetyl parabanic acid decomposed 20-30^o above its melting point. Hydrolysis of the acetyl derivatives was studied by ¹H nmr spectroscopy. In the presence of adventitious water in the solvent diacetylparabanic acid gives, initially, the monoacetyl derivative and acetic acid, followed by ring opening to N-acetyloxaluric acid. This ease of hydrolysis reduces its attractiveness as a potential gas generator. An X-ray crystallographic determination was carried out on diacetylparabanic acid and the significance of the bond lengths in the hydrolysis process is discussed. N,N'-Adipoyldi-parabanic acid was prepared in low yield and decomposed ca 20^o above its melting point.

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 39-40).
We study the problem of distributed correlation generators wherein n parties wish to simulate unbounded samples from a joint distribution D = Di x D2 X ... x D[subscript n], once they are initialized using randomness sampled from a (possibly different) correlated distribution. We wish to ensure that these samples are computationally indistinguishable from i.i.d. samples from D. Furthermore, we wish to ensure security even against an adversary who corrupts a subset of the parties and obtains their internal (initialization) state. Our contributions are three-fold. First, we define the notion of distributed (noninteractive) correlation generators and show its connection to other cryptographic primitives. Secondly, assuming the existence of indistinguishability obfuscators, we show a construction of distributed correlation generators for a large and natural class of joint distributions that we call conditionally sampleable distributions. Finally, we show a construction for the subclass of additive-spooky distributions assuming private constrained pseudorandom functions (private CPRFs).
by Joseph Hui.
S.M.
S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

Dielectric Elastomer Generators (DEGs) are an emerging technology able to answer the need for cheap and available energy solutions, from energy scavenging at small scale to energy generation in large devices. Consisting of rubbery stretchable capacitors, DEG scan convert mechanical energy into electrical energy when their charges are displaced against the electric field during their relaxing phase. Despite having characteristics such as high energy density, low cost, and easy scalability, there are still significant challenges in their implementation. This includes the need for high voltage priming to enable the energy conversion and the adequate timing to charge/discharge the DEG. This thesis seeks to investigate and propose solutions for smart charge management in DEGs at different scales. Starting from a model-based analysis of the energy conversion phenomenon during the charging and discharging transients, we describe how undesired electrical-to-mechanical energy conversion, exhibited as an actuator-like effect, can reduce the overall energy generated during a cycle. Subsequently, we analyse different layouts of Self-Priming Circuits (SPCs), a scheme to passively promote the charge and discharge of DEGs. SPC-DEG systems can receive low voltage priming and then increase the system voltage and the amount of energy generated per cycle, eliminating the need for a high voltage time-controlled charge. Our model is experimentally validated and gives good quantitative accuracy. Using the SPC-DEG model and considering the actuator-like behaviour, we predict that the SPC-DEG systems can undergo a self-stabilising condition, which we then verify experimentally, and propose methods to estimate the emergent steady state. In addition, we develop the Self-sensing Peak Detection (SSPD) method that self-senses the deformation characteristic of DEGs and uses it as a signal to autonomously promote charge and discharge. The method was successfully implemented experimentally and has potential to optimally control DEG cycles even for unpredictable frequency and amplitude deformations. This thesis demonstrates possible solutions for charge management of DEGs and their implementation in the future.

The principal aim of this project is to study the energy production by solar energy system in close to the consumers and integrated into a microgrid. Microgrids are small-scale versions of today’s huge centralized electricity system, where it can generate, distribute and regulate the flow of electricity to consumers. Microgrids are able to feature the latest smart technology that increases efficiency and reliability and to create islands of sustainable energy within the larger grid. The main benefits of microgrids are: •Microgrids increase power supply reliability. •Microgrids make it easier to efficiently meet growing consumer demand. •Microgrids make it possible to deploy clean, renewable energy. The report gives an overview of the generator technologies, and discusses the characteristics of a microgrid and the barriers that have to be overcome if microgrids are to be deployed in Australia. A focus of the study is a microgrid of domestic users (housing estate) powered by photovoltaics (PV). In addition, this project will propose a method to evaluate the reliability of customers contracted with microgrid including distributed generators (DG) and power storage devices. A model of the energy consumption is used to produce typical profiles for the electricity consumption. Focusing on the balance between generation and load, a methodology has been developed to determine the optimum combination of generators and energy storage in the microgrid. It is found that a microgrid consisting of around 3kW (max peak) per household and 50% reduction of the electricity consumption will maintain energy balance on a yearly basis if supplemented by energy storage. The principle conclusion is that microgrids do have real potential to make a major contribution to reducing Green house Gas Emissions from building.

Hydropower maintains its position as the most important source of renewable electric energy in the world. The efficiency of large hydropower plants is unsurpassed, and after more than hundred years of development, the technology is mature and highly reliable. While new hydro resources are currently being developed in Asia and South America, most European countries go through a phase of intense refurbishment and upgrading of existing plants. Challenges faced by the hydropower industry include a knowledge transfer to new generations and the adaptation of unit designs to meet new operational requirements. As with all branches of engineering, the use of computerized design tools has revolutionized the art of hydropower plant design and the analysis of its performance. In the present work, modern tools like coupled field-circuit models and semi-analytic permeance models are used to address different aspects of electromagnetic analysis of generators in large hydropower plants. The results include the presentation of a mathematical model that uses concepts from rotating field theory to determine the air-gap flux density waveform in a hydroelectric generator. The model was succesfully used to evaluate armature voltage harmonics and damper bar currents at no-load and load conditions. A second study is concerned with the importance of losses due to rotational fields in core loss calculations. It is found that dynamic and rotational effects typically increase the total core loss estimates with about 28% in large hydroelectric generators. In a third study, linear models for the calculation of salient pole shoe form factors at an arbitrary level of magnetic loading are presented. The effect of the damper winding configuration on the damping capability of salient-pole generators is then evaluated in a separate study. The predicted impact of the coupling between damper cages on adjacent poles on the damping torque production is verified in a set of experiments.

The basis of this research is the augmentation of turbulent boundary layer stability. Here stability is referred to as ,the boundary layer's ability to withstand adverse pressure gradient and therefore separation. A practical example of an' issue involving a requirement for greater stability, where separation is a typical and detrimental feature, would be a deployed flap during a critical regime of the flight envelope such as landing. A sub-boundary layer vortex generator (SBVG) is a static flow control device which does not carry the drag penalty of its traditional larger counterparts. It is however less effective. An excited SBVG may be more effective than a static model, in terms of enhancement of stability, with the added benefit of not requiring sophisticated feedback systems to prevent the device from generating detrimental effects during periods other than the flight regime for which it is intended to operate, since the SBVG is embedded within the boundary layer. Here an SBVG was oscillated (or swept) between three inclination ranges at a number of frequencies. The swept inclination ranges were 16° to 24°, 20° to 28° and 24° to 32°. These motions were executed at reduced frequencies of 0.1,0.6, 1.6,3.1,4.7, and 6.3. The data show that dynamic actuation of a sub-boundary layer vortex generator results in a weaker vortex with accelerated decay than is generated by a static vortex generator at equivalent incidence. The strength and persistence of the dynamically generated vortex is closely linked with the reduced frequency, in that increase in frequency results in an increasingly weak vortex with an increasing rate of decay.

Random numbers are essential in many computer applications and games. The goal of this report is to examine two of the most commonly used random number generators and try to determine some of their strengths and weaknesses. These generators are the Linear Congruential Generator(LCG) and the Mersenne Twister(MT). The main objective will be to determine which one of these is the most optimal for low intensive usage and everyday work. Although some of the test results were in conclusive,there were some indications that MT is the better Pseudorandom Number Generator (PRNG) and therefore the preferred PRNG. However, be wary that this is not a general guideline and some implementations may differ from this.The final verdict was thus that MT is a more favourable option(mainly due to its speed) for everyday work, bothon a practical and theoretical level, if a choice should arise between the two options.
Slumptal representerar en viktig komponent i många datorspel, simulationer och övriga progam. Två av de mest förekommande slumptalsgeneratorerna är Linjär kongruensgeneratorn (LKG) samt Mersenne Twister(MT). Huvudfrågan som skall besvaras i denna rapport är huruvida, för vardagligt bruk, den ena generatorn är att föredra framför den andra. Ett antal tester kommer att utföras för att försöka finna eventuella styrkor samt svagheter med respektive generator.Baserat på ett fåtal tester är MT att föredra framför LKG. Detta stämmer väl överens med teorin. Notera dock att detta inte alltid gäller och att det kan förekomma skiljaktigheter mellan de båda alternativen som strider mot det tidigare påståendet. Detta är främst beroende på vilka implementationer som används för respektive generator. Slutsatsen är således att användning av MT ändå rekommenderasframför LKG, främst på grund av den snabba genereringshastigheten för MT.

This report is a literary study on provably secure pseudo-random generators. In the report we explain what provably secure pseudo-random generators are and what they are most commonly used for. We also discuss one-way functions which are closely related to our subject. Furthermore, two well-known generators are described and compared, one generator by Blum and Micali, and one by Blum, Blum and Shub. What we have concluded is that the x 2 mod N generator by Blum, Blum and Shub seems to be the better one concerning speed, security and application areas. You will also be able to read about how the Blum-Blum-Shub generator can be implemented and why we believe that implementation is suitable.
Den här rapporten är en litteraturstudie om bevisbart säkra pseudo-slumpmässiga generatorer. I rapporten förklarar vi vad bevisbart säkra pseudo-slumpmässiga generatorer är och vad de vanligtvis används till. Vi tar dessutom upp envägsfunktioner som är starkt kopplat till vårt ämne. Vidare beskrivs och jämförs två kända sådana generatorer, en generator av Blum och Micali och en generator av Blum, Blum och Shub. Den slutsats som vi kommit fram till är att x 2 mod N generatorn av Blum, Blum och Shub verkar vara den bättre utav dem vad gäller hastighet, säkerhet och applikationsområden. Ni kommer även kunna läsa om hur en sådan generator kan implementeras och vi förklarar varför den presenterade koden är bra.

Compared with algorithms specialized for a single distribution universal (also called automatic or black-box) algorithms for continuous distributions were relatively seldom discussed. But they have important advantages for the user: One algorithm coded and tested only once can do the same or even more than a whole library of standard routines. It is only necessary to have a program available that can evaluate the density of the distribution up to a multiplicative factor. In this paper we show that transformed density rejection is well suited to construct universal algorithms suitable for correlation induction which is important for variance reduction in simulation. (author's abstract)
Series: Preprint Series / Department of Applied Statistics and Data Processing

The key question this thesis aims to address is to what extent can micro-generation sources contribute to the carbon emission reduction targets set by the UK government. The operational emissions of micro-CHP capable micro-generators were examined against the UK grid electricity and gas boiler heat. Fossil and biomass fuels were considered. The life-cycle emissions associated with the manufacturing, transport and disposal of micro-generators were calculated. Case studies were constructed, based on the literature. It was found that emissions associated with domestic electrical and thermal demand would be reduced significantly. A Virtual Power Plant (VPP) was defined for aggregating micro-generators, using micro-generation penetration projections for the year 2030 from the literature. An optimisation problem was described, where the goal was to minimise the VPP carbon emissions. The results show the amount of emissions that would potentially be reduced by managing an existing micro-generation portfolio in a VPP. An Environmental Virtual Power Plant (EVPP) was defined, for controlling micro-generator carbon emissions. A multi-agent system was designed. The principle of operation resembles an Emissions Trading Scheme. Emission allowances are traded by the micro-generators, in order to meet their emissions needs. Three EVPP control policies were identified. Fuzzy logic was utilised for the decision making processes. Simulations were performed to test the EVPP operation. The main benefit for the micro-generators is the ability to participate in markets from which they would normally be excluded due to their small size. The multi-agent system was verified experimentally using micro-generation sources installed in two laboratories, in Athens, Greece. Two days of experiments were performed. Results show that system emissions have been successfully controlled, since only small deviations between desired and actual emissions output were observed. It was found that Environmental Virtual Power Plant controllability increases significantly by increasing the number of participating micro-generators.

Aufgrund von steigenden Energiekosten und einer sukzessive steigenden öffentlichen sowie politischen Forderung nach Umweltbewusstsein und Nachhaltigkeit, ist die Effizienzsteigerung von Gesamtsystemen einer der treibenden Kräfte für innovative, technologische Neuheiten geworden. Besonders bei der Entwicklung von verbrennungsmotorisch angetriebenen Fahrzeugen wurden z.B. durch die Hybridisierung von Antriebssträngen, die die Rekuperation von kinetischer Energie ermöglichen, Technologien zur Energieeinsparung etabliert. Da bei Verbrennungsmotoren ein hoher Anteil der im Kraftstoff gespeicherten Energie technologiebedingt als Abwärme im Abgas verloren geht, bietet die Wärmerekuperation ein weiteres hohes Potential für weitere Einsparungen. Diese ist z.B. mit Hilfe von thermoelektrischen Generatoren (TEG) möglich, die einen Wärmestrom direkt in elektrische Energie umwandeln. Zur effizienten TEG-Systemgestaltung ist ein hoher Temperaturgradient über dem thermoelektrisch aktivem Material notwendig, der wiederum zu kritischen thermomechanischen Spannungen im Bauteil führen kann. Diese werden zum einen durch die unterschiedlichen Temperaturausdehnungskoeffizienten der verschiedenen Materialien und zum anderen durch die mechanische Anbindung auf der heißen und kalten Seite des TEG verursacht. Somit liegt ein Zielkonflikt zwischen dem thermoelektrischen Systemwirkungsgrad und der mechanischen Festigkeit des Bauteils vor. In dieser Arbeit wird mit Hilfe einer mehrkriteriellen Parameteroptimierung eines vollparametrisierten FE-Modells des TEG in ANSYS WORKBENCH eine Methode vorgestellt, den thermoelektrischen Wirkungsgrad bei gleichzeitiger Reduktion der thermomechanischen Spannungen zu optimieren. Zur Optimierung kommt dabei ein genetischer Algorithmus der MATLAB GLOBAL OPTIMIZATION TOOLBOX zum Einsatz. Der Modellaufbau wird in ANSYS WORKBENCH mit der Makro-Programmiersprache JSCRIPT realisiert. Als Ziel- und Bewertungsfunktionen wird die mechanische Belastung jedes Bauteils im TEG ausgewertet und dessen elektrische Leistungsdichte berechnet. Die Ergebnisse zeigen, dass mit Hilfe der vorgestellten Methodik eine paretooptimale Lösung gefunden werden kann, die den gestellten Anforderungen entspricht.

The global demand for renewable energy is forecast to grow rapidly over the next 25 years [1]. A class of variable capacitor power generators called Dielectric Elastomer Generators (DEG), show considerable promise for harvesting from previously unviable sources. This is because they can be directly coupled to large broadband motions without gearing, while maintaining a high energy density, and they have few moving parts, and are highly flexible. At the system level DEG cannot currently realize their full potential for flexibility, simplicity and low mass because they require rigid and bulky external circuitry and often need a secondary high voltage energy source; there is a lack of modelling tools for system level optimization; and there is a lack of experimental data from explicitly described DEG systems. The objectives of this thesis are to provide solutions to these issues. First, system level DEG models with the dynamic electrical systems were developed and experimentally validated. Then the generalized Self-Priming Circuit (SPC) was introduced, an external circuit that enables DEG to operate in a wide range of conditions without a secondary high voltage energy source. These systems do not require an external high voltage energy source because they have the ability to boost their voltage from consumer battery levels up to kilovolt levels by accumulation of generated energy. Generalized SPC were then optimized for voltage boosting and energy production using the system level models. Finally, integrated self-priming systems were introduced. The SPC in these systems was integrated onto the DEG membrane using a flexible electronics technology called Dielectric Elastomer Switches (DES), so that no rigid and bulky external electronics were required. Highly explicit experimental analysis of each system was carried out. These contributions resulted in the publication of three journal articles, two provisional patents, and three conference articles. This work presents the opportunity to produce DEG systems with greater autonomy, softness, simplicity, energy density, and lower cost than previously. With further developments of DES, more complex systems with these benefits will be possible.

Monte Carlo simulations are embarrassingly parallel in nature, so having a parallel and efficient random number generator becomes crucial. To have a parallel generator with uncorrelated processors, parallelization methods are implemented together with a binary tree mapping. Although, this method has considerable advantages, because of the constraints arising from the binary tree structure, a situation defined as problem of falling off the tree occurs. In this thesis, a new spawning method that is based on binary tree traversal and new spawn processor appointment is proposed to use when falling off the tree problem is encountered. With this method, it is seen that, spawning operation becomes more costly but the independency of parallel processors is guaranteed. In Monte Carlo simulations, random number generation time should be unperceivable when compared with the execution time of the whole simulation. That is why
linear congruential generators with Mersenne prime moduli are used. In highly branching Monte Carlo simulations, cost of parameterization also gains importance and it becomes reasonable to consider other types of primes or other parallelization methods that provide different balance between parameterization cost and random number generation cost. With this idea in mind, in this thesis, for improving performance of linear congruential generators, two approaches are proposed. First one is using Sophie-Germain primes as moduli and second one is using a hybrid method combining both parameterization and splitting techniques. Performance consequences of Sophie-Germain primes over Mersenne primes are shown through graphics. It is observed that for some cases proposed approaches have better performance consequences.

Turkish Electricity Market is modeled as a non-cooperative game with complete information in order to simulate the behavior of market participants and analyze their possible strategies. Player strategies are represented with multipliers in a discrete strategy set. Different market scenarios are tested through different game settings. As the novelty of this thesis, similar market participants are clustered and treated as single players in order to apply game theory in an efficient way. Generators are clustered using Agglomerative Hierarchical Clustering and Square Sum of Deviations is used as the proximity measure. The game is constructed with three players that reflect the main characteristics of the market participants. Clusters and game scenarios are constructed using the real market data of the Turkish Electricity Market at four different time points in 2008 and results are compared. Clustering results reflect the actual installed capacity distribution based on the main companies and fuel types in Turkish Electricity Market. According to four games of clustered electricity generators, when there is not enough competition in the market, dominant player is advised to submit bids with lower price for energy surplus cases and offers with higher price for energy deficit cases. However, when there is competition in the market, players are advised to submit offers with lower price in order to take a share of the limited demand for up-regulation.

This thesis presents a study on the design method to optimise the performance for producing green power from multiple renewable energy generators. The design method is presented through PLC (Programmable Logic Controller) theory. All the digital and analogue inputs are connected to the input cards. According to different operations conditions for each generator, the PLC will image all the inputs and outputs, from these images; a software program has been built to create a control method for multiple renewable energy generators to optimise production of green power. A control voltage will supply the output contractor from each generator via an interface relay. Three renewable generators (wind, solar, battery bank) have been used in the model system and the fourth generator is the back up diesel generator. The priority is for the wind generator due to availability of wind 24 hours a day, then solar, battery bank, and LPG or Diesel generators. Interlocking between the operations of the four contractors has been built to prevent interface between them. Change over between contractors, according to the generator's change over has also been built, so that it will delay supplying the main bus bar to prevent sudden supply to the load. Further study for controlling multiple renewable energy generators for different conditions such as controlling the multi-renewable energy generators from remote, or supplying weather forecast data from bureau of meteorology to the PLC directly as recommended.
Master of Electrical Engineering (Hons)

We develop a simplified one-dimensional numerical model that simulates the performance of thermoelectric generators (TEG). The model is based on the energy and electrical potential field equations. The Seebeck coefficient, thermal conductivity, electrical resistivity and Thomson coefficient of the TEG material are used to predict the harvested power. Bismuth-telluride is used as semiconductors materials of the TEG, which is the most commonly used material by industry. Experiments on three TEG modules were performed to validate the numerical model. A comparison with predicted levels of harvested energy based on the TEG specifications is also performed. The results show differences between the experimental and numerical values on one hand and the predicted ones on the other hand. The reason for these differences are discussed. A procedure to estimate the sensitivity of the harvested power to different inputs and TEG parameters is detailed. In the second part of the dissertation, we integrate a thermoelectric generator with an organic storage device. The performance of the integrated system for different values of load resistances and temperature gradients is determined. Finally, we demonstrate that power generated from a TEG is related to the flow rate in a pipe and can, thus, be used as a flow meter. Particularly, a dimensionless relation between the TEG's peak power and Reynolds number is determined.
Ph. D.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Randomness is one of the most intriguing, inspiring and debated topics in the history of the world. It appears every time we wonder about our existence, about the way we are, e.g. Do we have free will? Is evolution a result of chance? It is also present in any attempt to understand our anchoring to the universe, and about the rules behind the universe itself, e.g. Why are we here and when and why did all this start? Is the universe deterministic or does unpredictability exist? Remarkably, randomness also plays a central role in the information era and technology. Random digits are used in communication protocols like Ethernet, in search engines and in processing algorithms as page rank. Randomness is also widely used in so-called Monte Carlo methods in physics, biology, chemistry, finance and mathematics, as well as in many other disciplines. However, the most iconic use of random digits is found in cryptography. Random numbers are used to generate cryptographic keys, which are the most basic element to provide security and privacy to any form of secure communication. This thesis has been carried out with the following questions in mind: Does randomness exist in photonics? If so, how do we mine it and how do we mine it in a massively scalable manner so that everyone can easily use it? Addressing these two questions lead us to combine tools from fundamental physics and engineering. The thesis starts with an in-depth study of the phase diffusion process in semiconductor lasers and its application to random number generation. In contrast to other physical processes based on deterministic laws of nature, the phase diffusion process has a pure quantum mechanical origin, and, as such, is an ideal source for generating truly unpredictable digits. First, we experimentally demonstrated the fastest quantum random number generation scheme ever reported (at the time), using components from the telecommunications industry only. Up to 40 Gb/s were demonstrated to be possible using a pulsed scheme. We then moved towards building prototypes and testing them with partners in supercomputation and fundamental research. In particular, the devices developed during this thesis were used in the landmark loophole- free Bell test experiments of 2015. In the process of building the technology, we started a new research focus as an attempt to answer the following question: How do we know that the digits that we generate are really coming from the phase diffusion process that we trust? As a result, we introduced the randomness metrology methodology, which can be used to derive quantitative bounds on the quality of any physical random number generation device. Finally, we moved towards miniaturisation of the technology by leveraging techniques from the photonic integrated circuits technology industry. The first fully integrated quantum random number generator was demonstrated using a novel two-laser scheme on an Indium Phosphide platform. In addition, we also demonstrated the integration of part of the technology on a Silicon Photonics platform, opening the door towards manufacturing in the most advanced semiconductor industry.
L’aleatorietat és un dels temes més intrigants, inspiradors i debatuts al llarg de la història. És un concepte que sorgeix quan ens preguntem sobre la nostra pròpia existència i de per què som com som. Tenim freewill? És l’evolució resultat de l’atzar? L’aleatorietat és també un tema que sorgeix quan intentem entendre la nostra relació amb l’univers mateix. Per què estem aquí? Quan o com va començar tot això? És l’univers una màquina determinista o hi ha cabuda per a l’atzar? Sorprenentment, l’aleatorietat també juga un paper crucial en l’era de la informació i la tecnologia. Els nombres aleatoris es fan servir en protocols de comunicació com Ethernet, en algoritmes de classificació i processat com Page Rank. També usem l’aleatorietat en els mètodes Monte Carlo, que s’utilitzen en els àmbits de la física, la biologia, la química, les finances o les matemàtiques. Malgrat això, l’aplicació més icònica per als nombres aleatoris la trobem en el camp de la criptografia o ciber-seguretat. Els nombres aleatoris es fan servir per a generar claus criptogràfiques, l’element bàsic que proporciona la seguretat i privacitat a les nostres comunicacions. Aquesta tesi parteix de la següent pregunta fonamental: Existeix l’aleatorietat a la fotònica? En cas afirmatiu, com podem extreure-la i ferla accessible a tothom? Per a afrontar aquestes dues preguntes, s’han combinat eines des de la física fonamental fins a l’enginyeria. La tesi parteix d’un estudi detallat del procés de difusió de fase en làsers semiconductors i de com aplicar aquest procés per a la generació de nombres aleatoris. A diferència d’altres processos físics basats en lleis deterministes de la natura, la difusió de fase té un origen purament quàntic, i per tant, és una font ideal per a generar nombres aleatoris. Primerament, i fent servir aquest procés de difusió de fase, vam crear el generador quàntic de nombres aleatoris més ràpid mai implementat (en aquell moment) fent servir, únicament, components de la indústria de les telecomunicacions. Més de 40 Gb/s van ser demostrats fent servir un esquema de làser polsat. Posteriorment, vam construir diversos prototips que van ser testejats en aplicacions de ciència fonamental i supercomputació. En particular, alguns dels prototips desenvolupats en aquesta tesi van ser claus en els famosos experiments loophole-free Bell tests realitzats l’any 2015. En el procés de construir aquests prototips, vam iniciar una nova línia de recerca per a intentar contestar una nova pregunta: Com sabem si els nombres aleatoris que generem realment sorgeixen del procés de difusió de fase, tal com nosaltres creiem? Com a resultat, vam introduir una nova metodologia, la metrologia de l’aleatorietat. Aquesta es pot fer servir per a derivar límits quantificables sobre la qualitat de qualsevol dispositiu de generació de nombres aleatoris físic. Finalment, ens vam moure en la direcció de la miniaturització de la tecnologia utilitzant tècniques de la indústria de la fotònica integrada. En particular, vam demostrar el primer generador de nombres aleatoris quàntic totalment integrat, fent servir un esquema de dos làsers en un xip de Fosfur d’Indi. En paral·lel, també vam demostrar la integració d’una part del dispositiu emprant tecnologia de Silici, obrint les portes, per tant, a la producció a gran escala a través de la indústria més avançada de semiconductors.
La aleatoriedad es uno de los temas más intrigantes, inspiradores y debatidos a lo largo de la historia. Es un concepto que surge cuando nos preguntamos sobre nuestra propia existencia y de por qué somos como somos. ¿Tenemos libre albedrío? ¿Es la evolución resultado del azar? La aleatoriedad es también un tema que surge cuando intentamos entender nuestra relación con el universo. ¿Por qué estamos aquí? ¿Cuándo y cómo empezó todo esto? ¿Es el universo una máquina determinista o existe espacio para el azar? Sorprendentemente, la aleatoriedad también juega un papel crucial en la era de la información y la tecnología. Los números aleatorios se usan en protocolos de comunicación como Ethernet, y en algoritmos de clasificación y procesado como Page Rank. También la utilizamos en los métodos Monte Carlo, que sirven en los ámbitos de la física, la biología, la química, las finanzas o las matemáticas. Sin embargo, la aplicación más icónica para los números aleatorios la encontramos en el campo de la criptografía y la ciberseguridad. Aquí, los números aleatorios se usan para generar claves criptográficas, proporcionando el elemento básico para dotar a nuestras comunicaciones de seguridad y privacidad. En esta tesis partimos de la siguiente pregunta fundamental: ¿Existe la aleatoriedad en la fotónica? En caso afirmativo, ¿Cómo podemos extraerla y hacerla accesible a todo el mundo? Para afrontar estas dos preguntas, se han combinado herramientas desde la física fundamental hasta la ingeniería. La tesis parte de un estudio detallado del proceso de difusión de fase en láseres semiconductores y de cómo aplicar este proceso para la generación de números aleatorios. A diferencia de otros procesos físicos basados en leyes deterministas de la naturaleza, la difusión de fase tiene un origen puramente cuántico y, por lo tanto, es una fuente ideal para generar números aleatorios. Primeramente, y utilizando este proceso de difusión de fase, creamos el generador cuántico de números aleatorios más rápido nunca implementado (en ese momento) utilizando únicamente componentes de la industria de las telecomunicaciones. Más de 40 Gb/s fueron demostrados utilizando un esquema de láser pulsado. Posteriormente, construimos varios prototipos que fueron testeados en aplicaciones de ciencia fundamental y supercomputación. En particular, algunos de los prototipos desarrollados en esta tesis fueron claves en los famosos experimentos Loophole-free Bell tests realizados en el 2015. En el proceso de construir estos prototipos, iniciamos una nueva línea de investigación para intentar dar respuesta a una nueva pregunta: ¿Cómo sabemos si los números aleatorios que generamos realmente surgen del proceso de difusión de fase, tal y como nosotros creemos? Como resultado introdujimos una nueva metodología, la metrología de la aleatoriedad. Esta se puede usar para derivar límites cuantificables sobre la calidad de cualquier dispositivo de generación de números aleatorios físico. Finalmente, nos movimos en la dirección de la miniaturización de la tecnología utilizando técnicas de la industria de la fotónica integrada. En particular, creamos el primer generador de números aleatorios cuántico totalmente integrado utilizando un esquema de dos láseres en un chip de Fosfuro de Indio. En paralelo, también demostramos la integración de una parte del dispositivo utilizando tecnología de Silicio, abriendo las puertas, por tanto, a la producción a gran escala a través de la industria más avanzada de semiconductores.

Spectrally pure signals are an indispensable requirement when the Signal Generator (SG) is to be used as part of a test bed. However, even sophisticated equipment may not comply with the needs imposed by certain applications. This work approaches the problem by using Digital Pre-Distortion (DPD) based on a polynomial memory-less model obtained for the SG.

Using the SG in arbitrary mode (ARB) an input signal is computer-generated and reproduced by the SG. Measurement accuracy is ensured using coherence sampling and grid matching to the Signal Analyzer (SA). Finally, careful time alignment is used to compare the transmitted and received three-tone signals to obtain the polynomials coefficients.

Results show that the accuracy of the model and the effectiveness of pre-distortion may vary depending on the amplitude of the three-tone signal. However, using polynomials of 5th and 9th degrees up to 15dB reduction of the 3rd order Inter-Modulation products can be obtained, and spurious powers may be lowered down to 70dBc.

It is the goal of this body of work to research an assortment of different photoacid generators (PAGs) and quantify their ability to perform the decomposition of poly(propylene carbonate) (PPC). Adding PAGs to PPC allows for a decreased polymer decomposition temperature, which can in turn be used as a sacrificial polymer for the fabrication of various microelectromechanical and microfluidic devices. A focus will be placed on relating the properties of the PAG such as acid strength, acid volatility, and PAG activation to processing issues like percentage of total film decomposition, amount and composition of film residue, decomposition rate, decomposition temperature, and environmental dependencies. This research discovered that the use of superacid triflic and nonaflic based PAGs were not adequate for the decomposition of PPC due to the high vapor pressure of the acid. Furthermore, the non-fluorinated sulfonic acid based PAGs do not posses the super-acid level acidity needed to sufficiently decompose PPC. Conversely, a perfluorinated methide and a tetrakis(pentafluoropheyl)borate based PAG both demonstrated the capability for high level PPC decomposition. Building on the knowledge gained through experimentation with these individual PAGs, the creation of a novel Combination PAG was accomplished. The Combination PAG uses acid groups with different physical properties collectively working to achieve what neither could complete individually.

This thesis proposes a novel method for implementing test pattern generators for Built-In Self Test (BIST) that eliminates the area and performance penalties associated with existing schemes. The method utilizes adders which are widely available in data-path architectures used in digital signal processing circuits and general purpose processors.
Arithmetic test pattern generators produce test patterns by continuously accumulating a constant value. The generated patterns provide complete state coverage on subspaces of contiguous bits and are thus, excellent sources of pseudo-exhaustive tests. In this thesis, several metrics are developed to evaluate the testing properties of different arithmetic generators. Synthesis techniques for a class of generators that exhaustively cover single size subspaces in an optimal manner are formulated. Other generators that best target various ranges of subspace sizes are identified using an efficient search algorithm. Generators with interleaved output spaces are also evaluated. Detailed tables listing the best generators are provided.
The proposed test pattern generation scheme, in conjunction with a previously introduced compaction scheme that uses similar existing hardware, now facilitates a non-intrusive, high quality BIST strategy for high performance data-path architectures. This strategy uses the functionality of existing hardware, is entirely integrated with the circuit under test, and permits at-speed testing, using simple BIST control, with no performance degradation or area overhead.

Air jet vortex generators are a boundary layer control device and as such can effect a significant delay to the stall of an aerofoil. They can also reattach a separated flow, as long as the angle of attack is less than the air jets 'on' stall angle. A wind tunnel model was built and tested and then modified to incorporate air jets. The air jets increased CL max by 55% and reduced the drag throughout the incidence range, a, for the chosen blowing pressure of 1 p. s. i. (6900Pa). By varying the air supply so that the jets operate between 'off' and fully 'on' a whole family bf aerofoil L/D characteristics could be derived. The blade set of a 150 kW stall regulated wind turbine was then modified with air jet vortex generators and tested at full scale. This was done primarily to increase its energy yield by reducing energy loss in the region of the power curve 'knee', but also to allow a degree of power regulation in high wind speeds. The air supply in this demonstration was supplied by a fan mounted on, and rotating with, the rotor. Full-scale trials demonstrated that air jets can indeed be used to straighten the power curve prior to rated wind speed. This important result means that a stall regulated machine can be made to behave in the same way as a pitch controlled machine without having to pitch the blades. Of the two air jet configurations tested in the wind tunnel, the second had an improved L/D characteristic and required less mass flow, even though the physical change was minor. This indicates that further optimisation of air jets may be achieved. Further wind tunnel testing showed that it should be possible to eliminate the fan used in the full scale trials and use one of two 'passive' blowing techniques. It was shown that the air jets can be supplied by air at atmospheric pressure due to the suction on the upper surface of the aerofoil which is sufficient to pull air through the jet exits and create vortices. However, to achieve an optimised air jet configuration and to investigate the possibilities of using passive blowing, air jet vortex generators will need to be modelled numerically, so that this innovative concept can be brought to market quickly.

In recent years, the efficiency of thermoelectric devices has improved greatly due thermoelectric material and device geometrical improvements. However, the efficiency of TEG is still low, being a subject of further research for more improvement. Hence, the main objective of the research carried out in this thesis is to analyse the performance of dc-dc converters with or without MPPT in conditioning the power generated from TEG. In light of this objective, the following case studies have been carried out. The initial study has analysed the performance of a TEG/dc-dc boost converter system. Results indicate that the converter is able to stabilise and boost the voltage and higher efficiencies are achieved at different hot side temperatures. The next study proposes the use of MPPT algorithm to harvest maximum power from TEG system. Hence, the analysis of the performance of TEG/dc-dc converter with MPPT enabled by Incremental conductance (IC) method is done. The results indicate that the IC based MPPT approach is able to track the maximum power point but with relatively lower efficiencies than the Perturb and Observe (P&O) based MPPT method. method. Another study has analysed the parameters for the performance of TEG/dc-dc converter system in different modes with a variable load. The TEG system is subjected to different hot side temperatures, including increasing step, increasing random and constant cold side temperature profiles. The study has demonstrated how the proper selection of converter components is a necessity to avoid converter losses as well interferences on the load connected to TEG/dc-dc converter system. Furthermore, another study compares the performance of extremum seeking control (ESC) and P&O MPPT algorithms applied to TEG system. The TEG model is validated with results from multiphysics (COMSOL) modelling software. To assess the effect of temperature dependency of TEG parameters, two TEG materials have been chosen; bismuth telluride (Bi2Te3) with temperature dependent Seebeck effect (S), electrical conductivity (σ) and thermal conductivity (k); and lead telluride (PbTe) with non-temperature dependent S, σ and k. Results indicate that ESC MPPT method outperforms the P&O technique in terms extracting maximum power and the simulation speed. Results also indicate that ESC outperforms the IC technique in terms of extracting maximum power and the speed of computation. ESC method is faster than the IC method. In the final study, the application of the concept and the design of a distributed dc-dc converter architecture (DCA) on TEG system is deliberated. The distributed or cascaded converter architecture involves the use of non-isolated per-TEG dc-dc converter connected to the load. Alternatively, for some specific loads, especially in automotive applications, soft-switched, isolated bi-directional dc-dc converters can be used instead of non-isolated converters because these integrated converters enable bi-directional power flow control capability. Simulations and experimental studies have been carried out to demonstrate and prove the necessity of the DCA design application on TEG systems. In addition, some of the factors affecting the performance of TEG systems are correspondingly analysed.

Random numbers find applications in a range of different fields, from quantum key distribution and classical cryptography to fundamental science. They also find extensive use in gambling and lotteries. By exploiting the probabilistic nature of Quantum Mechanics, quantum random number generators (QRNGs) provide a secure and efficient means to produce random numbers. Most of the quantum random number generators demonstrated so far have been built in bulk optics, either using free space or fibre-optic components. While showing good performance, most of these demonstrations are strongly limited in real life applications, due to issues such as size, costs and the manufacturing process. In this thesis I report the demonstration of three different QRNGs based on integrated photonics. First, I demonstrated a QRNG based on homodyne measurement of optical vacuum states on a Silicon-on-insulator (SOI) chip. Second, I developed a SOI QRNG based on phase fluctuations from a laser diode. In these two schemes all the optical and opto-electronic components, excluding the laser, were integrated onto a silicon-on-insulator device. These schemes, being built on a silicon-on-insulator chip are potentially CMOS compatible and pave the way for being integrated onto other more complex systems. These QRNGs showed Gbps generation rates and passed the statistical tests provided by NIST. Third, I report the preliminary study of a QRNG based on homodyne measurement of optical vacuum states onto a Indium Phosphide (InP) chip. In this third experiment, all the components, including a laser diode, were monolithically integrated in the same chip, which provide a great advantage in terms of the overall size of the optics of the device.

Thesis: S.M. in Computer Science and Engineering, Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 61-64).
In the study of cryptography in NCO, it was previously known that Goldreich's candidate pseudorandom generator (PRG) is insecure when instantiated with a predicate P in 4 or fewer variables, if one wants to achieve polynomial stretch. On the other hand, there is a standard candidate PRG with locality 5 based on the "tri-sum-and" predicate ... However, locality is only one complexity measure of a PRG that one could hope to minimize. In this work, we consider the problem of minimizing three other complexity measures of a (local) PRG: decision tree (DT-)complexity, Q-degree (i.e., the degree of P as a polynomial over Q), and the recent notion of blockwise locality (due to Lin and Tessaro). These three complexity measures are all of interest for their possible applications to constructing indistinguishability obfuscation (IO) schemes based on low-degree multilinear maps. Indeed, Lin and Tessaro recently proposed an intriguing candidate IO scheme based on bilinear maps and a non-standard assumption on "Goldreich-like" pseudorandom generators. We obtain both positive and negative results on the existence of low complexity PRGs. First, we give a candidate predicate for Goldreich's PRG with DT-complexity 4 and Q-degree 3. We also show that all predicates with either DT-complexity less than 4 or Q-degree less than 3 yield insecure PRGs, so our candidate predicate simultaneously achieves the best possible locality, DT-complexity, Q-degree, and F2-degree according to all known attacks. Finally, we show polynomial-time attacks on the blockwise 2-local PRGs required in the Lin-Tessaro work, invalidating the security of their IO and FE candidates based on bilinear maps. Our attack uses tools from the literature on two-source extractors (Chor and Goldreich, SICOMP 1988) and efficient refutation of random 2-XOR instances (Charikar and Wirth, FOCS 2004).
by Alex Lombardi.
S.M. in Computer Science and Engineering

Thermoelectric generators (TEGs) convert the thermal energy flowing through them into DC electrical energy in a quantity dependant on the temperature difference across them and the electrical load applied, with a conversion efficiency of typically 5%. Nonetheless, they can be successfully employed to recover energy from waste heat and their use has increased rapidly in recent years, with applications ranging from microwatts to kilowatts, due to energy policy legislations and increasing energy cost determined by climate change, environmental issues and availability of energy sources. The performance of TEGs, subject to thermal and electrical effects, can vary considerably depending on the operating conditions, therefore it is necessary to measure and characterise their performance, and to understand their dynamic behaviour and interaction with the other parts of the system. Based on this knowledge it is then desired to develop an effective electronic system able to control these devices so as to maximise the power generated and increase the overall efficiency of the system. Several TEGs can be electrically connected in series and/or parallel (forming an array) to provide the required voltage and/or current. However, TEGs are usually employed in environments with time-varying temperatures, thermal powers and electrical loads. As a consequence in most TEG systems the individual thermoelectric devices can be subject to temperature mismatch due to operating conditions. Therefore it is of relevant importance to accurately simulate the evolution of thermoelectric systems during thermal and electrical transients. At the same time accurate experimental performance data are necessary to permit precise simulations. Unfortunately, there is still no standardised method to test the electrical and thermal performance of TEGs. This thesis tackles these key challenges and contributes to the pool of existing knowledge about TEGs dealing with four main topics: testing of thermoelectric generators, simulation of thermoelectric generating systems, design and production of power electronic converters for thermoelectric generators, and physical applications of thermoelectric generators. After an introduction to the physical phenomena underlying the operation of TEGs, this thesis describes the innovative test system built at the University of Glasgow to assess the performance of TEG devices in the ”real-world”. The fixture allows a single TEG device to be tested with thermal input power up to 1 kW and hot temperature up to 800◦C with minimal thermal losses and thermal shock; the mechanical clamping force can be adjusted up to 5 kN, and the temperatures are sensed by thermocouples placed directly on the TEGs surfaces. A computer program controls all the instruments in order to minimise errors and to aid accurate measurement and test repeatability. The test rig can measure four TEGs simultaneously, each one individually controlled and heated. This allows testing the performance of TEG arrays under mismatched conditions, e.g., dimensions, clamping force, temperature, etc. Under these circumstances experimental results and a mathematical analysis show that when in operation each TEG in the array will have a different electrical operating point at which maximum energy can be extracted and problems of decreased power output arise. This thesis provides the transient solution to the one-dimensional heat conduction equation with internal heat generation that describes the transfer and generation of heat throughout a thermoelectric device with dynamic exchange of heat through the hot and cold sides. This solution is then included in a model in which the Peltier effect, the thermal masses and the electrical behaviour of the system are also considered. The resulting model is created in Simulink and the comparison with experimental results from a TEG system confirms the accuracy of the simulation tool to predict the evolution of the thermoelectric system both in steady-state and during thermal or electrical transients. This thesis presents an investigation of the optimum electrical operating load to maximise the power produced by a TEG. Both fixed temperature difference and fixed thermal input power conditions are considered. Power electronic converters controlled by a Maximum Power Point Tracking (MPPT) algorithm are used to maximise the power transfer from the TEG to the load. The MPPT method based on the open-circuit voltage is arguably the most suitable for the almost linear electrical characteristic of TEGs. An innovative way to perform the open-circuit voltage measurement during the pseudo-normal operation of the power converter is presented. This MPPT technique is supported by theoretical analysis and used to control an efficient synchronous Buck-Boost converter capable of interfacing TEGs over a wide range of temperatures. The prototype MPPT converter is controlled by an inexpensive microcontroller, and a lead-acid battery is used to accumulate the harvested energy. Experimental results using commercial TEG devices demonstrate the ability of the MPPT converter to accurately track the maximum power point during steady-state and thermal transients. This thesis also presents two practical applications of TEGs. The first application exploits the thermal energy generated by a stove to concurrently produce electrical energy and heat water, while the second application recovers the heat energy rejected to ambient by a car’s exhaust gas system to generate electrical energy for battery charging.

This thesis describes four novel superconducting machine concepts, in the pursuit of finding a suitable design for large offshore wind turbines. The designs should be reliable, modular and light-weight. The main novelty of the topologies reside in using a single loop shaped stationary superconducting field winding, which eliminates the rotating transfer couplers and electric brushes or brushless exciters. Furthermore, the electromagnetic forces in the superconducting wire are also eliminated, which simplifies the design and manufacturing of the cryostat and the support structure. Among the four topologies presented, the claw pole type machine is the most promising one. The rotor of the machine composes of claw-poles made from laminated electrical sheets, the superconducting field winding and the armature winding are stationary. The machine is analysed using 3D FEA simulations and a small linear machine prototype is manufactured to verify the simulations. For large scale applications, a double-sided claw pole machine is proposed, which has balanced magnetic attraction forces in the rotor. The machine has a modular cryostat structure, which increases the availability of the machine. Thus, even if a fault occurs in the cryocoolers or in the armature coils, the rest of the machine can operate at partial load until the maintenance is performed. Moreover, it is much easier to replace the faulty parts, as full disassemble of the machine is not required, and a small on-site crane can be used. As a result, it offers operational advantages over the existing superconducting topologies. A 10 MW, 10 rpm generator design is presented, which has a diameter of 6.6 m and an axial length of 1.4 m. The total active mass of the generator is 58 tonnes, and the structural mass is 126 tonnes, which gives a total mass of 184 tonnes. There are four independent cryostats and two independent armature windings in the machine to improve modularity. The biggest advantage of the design is the significantly less superconducting wire usage compared to any other designs; 10 MW machine just needs 15 km of MgB2 wire at 30 K. Thus, it is believed that the proposed topology is a very cost effective and suitable candidate for a successful entry to the wind turbine market.

This thesis discusses, evaluates and, where possible, demonstrates the opening and closing stages of switching techniques and circuit arrangements needed to condition (sharpen) the output current pulse of a helical flux compression generator. The sharp rise in resistance that accompanies the rapid fusing of a thin metal foil (termed a fuse) opens the circuit in the initial stages, and a fast-acting plasma erosion switch (PEOS) whose output circuit is magnetically insulated at the end of its opening phase provides the same duty in the final stage. The study is directed towards a generator having a 1-to-2 MJ and multi-MA rating accumulated in about 150 microseconds, the ultimate aim being to produce an output current pulse rising to several hundred kiloamperes in approximately ten nanoseconds in a short circuit load, the accompanying loss of energy being of secondary importance. Additionally, the output circuit needs to be able to sustain high-voltages (MV) rising in a few nanoseconds across a purely resistive load.

The ever-increasing demand for power, and the correspondingly greater complexity of power systems, is leading to more severe problems of system reliability. Modern society is so dependent on the usage of electrical power that even a short interruption of service can cause serious problems. A public utility cannot be expected to provide a perfect power supply, since many of the possible causes of a power disturbance are beyond its control. The windings of small diesel-driven three-phase generator sets are often capable of being connected in either a zig-zag or an Edison-delta arrangement, to provide a single-phase supply for standby or emergency purposes. Although many of these generators are genuinely on standby (i.e. they are brought into operation only as a result of a system failure), many others operate continuously in situations where no mains supply is available. The thesis aims to investigate both the steady-state and the dynamic performance of a three-phase salient-pole generator, when reconnected in either a zig-zag or an Edison-delta configuration, and to provide a performance comparison with the more familiar modes of single-phase operation involving line-to-line and line-to-neutral loading. Symmetrical components are used to investigate the steady-state performance and a phase model is used to determine both the steady state and transient performance. Analytical expressions are obtained for the short-circuit currents for various generator connections by utilizing the modified Clarke transformation. The theoretical results from various models are compared with experimental results on a test machine. Losses, efficiency and voltage waveforms for various generator connections are experimentally obtained for the test machine. Results are discussed and suggestions for future research are included.

Power harvesting from thermoelectric generators is considered as a viable route towards sustainable energy generation by the conversion of thermal gradients occuring naturally or from waste heat sources into useful electrical energy. This thesis investigates the electrodeposition of n-type binary, ternary and doped thermoelectric materials, with the aim of demonstrating that electrodeposition can be used as a cost-effective and simple technique to fabricate highly-efficient thermoelectric materials. In order to achieve this, the thermoelectric and electrical properties of such materials must be related to their microstructural properties. Therefore, a detailed and systematic study of their microstructural properties, including morphology, crystal structure, composition and crystallite size, is undertaken whilst also measuring the electrical and thermoelectric properties. It is found that the potential of the working electrode, employed as the substrate during the electrodeposition of bismuth telluride, is one of the most effective variables in the fabrication process. More anodic potentials such as 0 V vs. SCE offer the best microstructural and thermoelectric properties. The addition of a surfactant, sodium lignosulphonate, to the electrolyte further improves the microstructural properties of bismuth telluride thin films, by levelling the deposits and inducing greater crystallographic orientation in growth planes perpendicular to the substrate. This is believed to be preferential for improving thermoelectric properties. The electrodeposition of the ternary thermoelectric material bismuth tellurium selenide shows that the microstructural and hence the thermoelectric and electrical properties of the thin films can be optimised by use of more positive electrode potentials. The thin films fabricated exhibit a thermoelectric efficiency of up to two orders of magnitude greater than similar materials prepared by electrodeposition previously and equal efficiency to those prepared by methods which are more costly and difficult to undertake. Doping these materials with copper, by electrochemical means, further improves the thermoelectric efficiency by over another order of magnitude.

Reliability is a key aspect of power system design and planning. In this research we present a reliability analysis algorithm for large scale, radially operated (with respect to substation), reconfigurable, electrical distribution systems. The algorithm takes into account equipment power handling constraints and converges in a matter of seconds on systems containing thousands of components. Linked lists of segments are employed in obtaining the rapid convergence. A power flow calculation is used to check the power handling constraints. The application of distributed generators for electrical distribution systems is a new technology. The placement of distributed generation and its effects on reliability is investigated. Previous reliability calculations have been performed for static load models and inherently make the assumption that system reliability is independent of load. The study presented here evaluates improvement in reliability over a time varying load curve. Reliability indices for load points and the overall system have been developed. A new reliability index is proposed. The new index makes it easier to locate areas where reliability needs to be improved. The usefulness of this new index is demonstrated with numerical examples.
Master of Science

The main purpose of this paper is to better understand groups that do not have the unique product property. In particular, the goal is to better understand Promislow's example, G, of such a group. In doing so, we will develop methods for generating examples of other sets that do not have the unique product property. With these methods we can show that there exists other distinct 14 element, square, non-unique product sets in G that are not inversions or translations. Also, this paper answers the question as to whether every non-unique product set can have only 14 elements in the negative by producing a 17 element square n.u.p. set. The secondary purpose of this paper is to demonstrate that in the group ring K[G], there are no units of support size 3.
Master of Science

Since the late 1960's mathematicians working mainly in the area of quantum field theory have used commutator estimates to prove self-adjointness of operators on Hilbert space. Recently, these results were extended and codified into a theory in the papers [BaR], [Rob 1], and [Rob 2]. The following thesis is based largely upon the above reports.

The taming of electricity and its widespread use allows people to see in the dark, to speak to one another instantaneously across the earth, and it allows retrieval of data from instruments sent out of the solar system. It is right to expect that the uses and demand for electricity will continue to grow, and to extend the ability to generate electricity; here two new micromachined devices for converting mechanical energy into electrical energy are presented. Aided by the wealth of micromachining process technology, generators that use an oscillatory motion to modify the physical structure of a capacitor with a built-in electric field provided by a permanent electret have been designed, built, and tested. The electret creates an electric field inside the capacitor structure, which induces mirror charge at some potential. The modification of the capacitor then generates an alternating displacement current through an external circuit, which provides useful electrical power. The electret microphone is a similar well known device for converting pressure waves into electrical signals by varying the distance between two charged capacitive plates. This work explores and proves feasible the ability to use mechanical forces to change the overlapping area of a charged capacitor structure and using mechanical forces to move a liquid into the gap of a charged capacitor structure, changing its permittivity to produce electricity. This work demonstrates 2.5mW of power from a 2cm diameter rotary generator at 12kRPM and 10[micro]w for a 0.1cm3 linear shaking generator at 60Hz.