Dissertations / Theses on the topic 'Next generation electronic'
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Sarat, Austin. "Interdisciplinary legal studies [electronic resource] : the next generation." Thesis, Bingley, UK : Emerald, 2010. http://hdl.handle.net/10945/7827.
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Approved for public release; distribution is unlimited"Hybrid" justice at the Special Court for Sierra Leone / Sara Kendall -- Surviving property : resistance against urban housing nationalization during the transformation to communism (Romania, 1950-1965) / Mihaela Serban Rosen -- Disciplinary evolution of Turkish prisons, 1980s-1990s / Arda Ibikoglu -- "I'm Gonna Call My Lawyer" : shifting legal consciousness at the intersection of inequality / Diana Hern©Øandez -- A more global court? : a call for a new perspective on judicial globalization and its effect on the U.S. Supreme Court / Angela Narasimhan -- The sovereign city? : negotiating self-determination in an American military enclave / Erin E. Fitz-Henry -- Technique and technology in the kitchen : comparing resistance to municipal trans fat and foie gras bans / Michaela DeSoucey and David Schleifer -- Indigeneity : before and beyond the law / Kathleen Birrell
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Ahmed, Iffat. "Multimedia quality improvements for next generation networks." Thesis, IMT Alti Studi Lucca, 2013. http://e-theses.imtlucca.it/115/1/Iffat_phdthesis.pdf.
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Video is foreseen to be dominant in the Internet and Next
Generation Networks, due to the increased usage of multimedia applications. The current Internet, and in particular the mobile Internet, was not designed with video requirements in mind and as a consequence, its architecture is very inefficient when handling video traffic. Not only is a policy optimization required, but it is also important to perform such an optimization in the proper manner. Therefore, providing Quality of Experience for such networks is an open issue and hot research area nowadays.
Our goal is to investigate the performance of the PHY/ Application cross-layer optimization, for which we developed
an analytical model to optimize the number of timeslots needed for a video to be correctly decoded with enhanced quality. The wireless channel is modeled by means of Markov chain, whose state represent different channel qualities. We exploit Crosslayer (PHY/ Application) solution with respect to application layer information about scalable video layers, and taking user channel status for adapting channel rates. This problem gets more crucial when the case of multicast is considered, as the base station needs to harmonize the heterogeneous requirements
of all the users and adapt transmission accordingly.
Performance is evaluated for various scenarios to investigate,
what is the optimum number of time slots needed for the base
layer of SVC, how does the feedback impacts on the end user
perceived quality and user satisfaction level, and to what extend
is Cross-layer optimization beneficial. Further, we evaluated
how the unicast extends to multicast and its impact on
end-user goodput, packet delivery delay and quality.
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Pezaros, D. "Network traffic measurement for the next generation Internet." Thesis, Lancaster University, 2005. http://eprints.lancs.ac.uk/12698/.
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Measurement-based performance evaluation of network traffic is a fundamental prerequisite for the provisioning of managed and controlled services in short timescales, as well as for enabling the accountability of network resources. The steady introduction and deployment of the Internet Protocol Next Generation (IPNG-IPv6) promises a network address space that can accommodate any device capable of generating a digital heart-beat. Under such a ubiquitous communication environment, Internet traffic measurement becomes of particular importance, especially for the assured provisioning of differentiated levels of service quality to the different application flows. The non-identical response of flows to the different types of network-imposed performance degradation and the foreseeable expansion of networked devices raise the need for ubiquitous measurement mechanisms that can be equally applicable to different applications and transports. This thesis introduces a new measurement technique that exploits native features of IPv6 to become an integral part of the Internet's operation, and to provide intrinsic support for performance measurements at the universally-present network layer. IPv6 Extension Headers have been used to carry both the triggers that invoke the measurement activity and the instantaneous measurement indicators in-line with the payload data itself, providing a high level of confidence that the behaviour of the real user traffic flows is observed. The in-line measurements mechanism has been critically compared and contrasted to existing measurement techniques, and its design and a software-based prototype implementation have been documented. The developed system has been used to provisionally evaluate numerous performance properties of a diverse set of application flows, over different-capacity IPv6 experimental configurations. Through experimentation and theoretical argumentation, it has been shown that IPv6-based, in-line measurements can form the basis for accurate and low-overhead performance assessment of network traffic flows in short time-scales, by being dynamically deployed where and when required in a multi-service Internet environment.
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Finney, Joseph. "Supporting continuous multimedia services in next generation mobile systems." Thesis, Lancaster University, 1999. http://eprints.lancs.ac.uk/11685/.
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Watanabe, Aruto. "Analysis of Crystal and Electronic Structures of Next Generation Cathode Materials." Kyoto University, 2020. http://hdl.handle.net/2433/253385.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第22549号
人博第952号
新制||人||226(附属図書館)
2019||人博||952(吉田南総合図書館)
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 内本 喜晴, 教授 吉田 寿雄, 准教授 戸﨑 充男
学位規則第4条第1項該当
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Raghunathan, Rajiv. "Virtual qualification methodology for next-generation area-array packages." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/18849.
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Glover, Garrett A. "The Next Generation Router System Cooling Design." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/191.
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Advancements in the networking and routing industry have created higher power electronic systems which dissipate large amounts of heat while cooling technology for these electronic systems has remained relatively unchanged. This report illustrates the development and testing of a hybrid liquid-air cooling system prototype implemented on Cisco’s 7609s router. Water was the working fluid through cold plates removing heat from line card components. The water was cooled by a compact liquid-air heat exchanger and circulated by two pumps. The testing results show that junction temperatures were maintained well below the 105°C limit for ambient conditions around 30°C at sea level. The estimated junction temperatures for Cisco’s standard ambient conditions of 50°C at 6,000 feet and 40°C at 10,000 feet were 104°C and 96°C respectively. Adjustments to the test data for Cisco’s two standard ambient conditions with expected device characteristics suggested the hybrid liquid-air cooling design could meet the projected heat load.
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Papakonstantinou, Athanasios. "Mechanism design for eliciting costly observations in next generation citizen sensor networks." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/143535/.
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Citizen sensor networks are open information systems in which members of the public act as information providers. The information distributed in such networks ranges from observations of events (e.g. noise measurements or monitoring of environmental parameters) to probabilistic estimates (e.g. projected traffic reports or weather forecasts). However, due to rapid advances in technology such as high speed mobile internet and sophisticated portable devices (from smart-phones to hand-held game consoles), it is expected that citizen sensor networks will evolve. This evolution will be driven by an increase in the number of information providers, since, in the future, it will be much easier to gather and communicate information at a large scale, which in turn, will trigger a transition to more commercial applications. Given this projected evolution, one key difference between future citizen sensor networks and conventional present ones is the emergence of self-interested behaviour, which can manifest in two main ways. First, information providers may choose to commit insufficient resources when producing their observations, and second, they may opt to misreport them. Both aspects of this self-interested behaviour are ignored in current citizen sensor networks. However, as their applications are broadened and commercial applications expand, information providers are likely to demand some kind of payment (e.g. real or virtual currency) for the information they provide. Naturally, those interested in buying this information, will also require guarantees of its quality. It is these issues that we deal with in this thesis through the introduction of a series of novel two-stage mechanisms, based on strictly proper scoring rules. We focus on strictly proper scoring rules, as they have been used in the past as a method of eliciting truthful reporting of predictions in various forecasting scenarios (most notably in weather forecasting). By using payments that are based on such scoring rules, our mechanisms effectively address the issue of selfish behaviour by motivating information providers in a citizen sensor network to, first, invest the resources required by the information buyer in the generation of their observations, and second, to report them truthfully. To begin with, we introduce a mechanism that allows the centre (acting as an information buyer) to select a single agent that can provide a costly observation at a minimum cost. This is the first time a mechanism has been derived for a setting in which the centre has no knowledge of the actual costs involved in the generation of the agents' observations. Building on this, we then make two further contributions to the state of the art, with the introduction of two extensions of this mechanism. First, we extend the mechanism so that it can be applied in a citizen sensor network where the information providers do not have the same resources available for the generation of their observations. These different capabilities are reflected in the quality of the provided observations. Hence, the centre must select multiple agents by eliciting their costs and the maximum precisions of their observations and then ask them to produce these observations. Second, we consider a setting where the information buyer cannot gain any knowledge of the actual outcome beyond what it receives through the agents' reports. Now, because the centre is not able to evaluate the providers' reported observations through external means, it has to rely solely on the reports it receives. It does this by fusing the reports together into one observation which then uses as a means to assess the reports of each of the providers. For the initial mechanism and each of the two extensions, we prove their economic properties (i.e. incentive compatibility and individual rationality) and then present empirical results comparing a number of specific scoring rules, which includes the quadratic, spherical, logarithmic and a parametric family of scoring rules. These results show that although the logarithmic scoring rule minimises the mean and variance of an agent's payment, using it may result in unbounded payments if an agent provides an observation of poor quality. Conversely, the payments of the parametric family exhibit finite bounds and are similar to those of the logarithmic rule for specific values of the parameter. Thus, we show that the parametric scoring rule is the best candidate in our setting. We empirically evaluate both extended mechanisms in the same way, and for the first extension, we show that the mechanism describes a family of possible ways to perform the agent selection, and that there is one that dominates all others. Finally, we compare both extensions with the peer prediction mechanism introduced by \cite{trustsr1} and show that in all three mechanisms the total expected payment is the same, while for both our mechanisms the variance in the total payment is significantly lower.
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Varghese, Thazhone Tijo. "Next Generation SDN Switches Using Programming Protocol-Independent Packet Processors." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254899.
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Over recent years, Software Defined Networking has enabled operators to control the network and realize new networking topologies. With increasing network traffic and protocol formats that aim at managing the traffic efficiently, the capabilities offered by Software Defined Networking alone are currently limited by the underlying fixed hardware infrastructure. The inflexibility involved in redesigning the hardware forces the bottom-up approach defined by switch vendors in describing the network and limits the capabilities offered to operators for further innovation. To meet the demands of ensuring a higher degree of flexibility to design, test and guarantee a faster time to market, the concept of Softly Defined Networks was introduced. The idea in addition to offering the conventional advantages of Software Defined Networking is based upon implementing a re-programmable data-plane. Field-Programmable Gate Arrays offered a higher degree of flexibility and capability to handle such designs. Programming Protocol-independent Packet Processors(P4) is a high-level language continuously evolving to define data-planes for various networking devices. The aim of P4 is for network operators to customize the underlying hardware with minimum constraints and ease, independent of the target. Therefore, the three major goals while defining such a language revolved around reconfigurability of hardware after being deployed, protocol independence to permit customization without constraints and target independence for users to be less concerned of the underlying hardware. Recent advances in P4 with the added support in terms of compatible targets and compilers have made P4 a viable opportunity to realize a re-programmable hardware. This work contributes towards exploring the ease of incorporating the capabilities of P4 in realizing a flexible data-plane. To achieve the same and study its characteristics a supporting two lane hardware pipeline is proposed that is capable of accommodating P4 upon a Kintex 7 FPGA. Primarily, a custom P4 module is defined that is capable of performing L2 operations upon a double tagged Ethernet frame using an appropriate architecture model. Subsequently, to integrate the P4 description on hardware the proposed supporting pipeline is implemented at a line rate of 10Gbps using the essential building blocks that help in observing the desired processing. Using a test setup, the design shall be further tested for the expected data-plane activity based upon the populated match-action rules. In terms of resource utilization, the overall design consumes less than 15% of the available resources and incurs an average latency of 5.71us. In addition to the ease of customization compared to the conventional fixed data-plane descriptions, it is vital to analyze the cost inherited while adopting P4. The final design is therefore studied in terms of resource utilization and latency by increasing the complexity of the P4 definition with regard to the number of headers, tables and write operations(H-T-W) for the adopted compiler. In the case of eight headers, tables and write operations(8H-8T-8W), there is an average latency of 8.01us and the P4 description alone demands 51536 LUTs, 77789 FFs and 118.5 BRAMs in terms of resource utilization. Finally, the article discusses the extent to which the proposed top-down approach is implemented and is capable of redefining the network as we know it.Under de senaste åren har Software Defined Networking gjort det möjligt för operatörer att styra nätverket och implementera nya nätverkstopologier. Med ökande nätverkstrafik och nya protokoll som syftar till att hantera trafiken effektivt, är de möjligheter som erbjuds av Software Defined Networking för närvarande begränsat av den underliggande fixa hårdvaruarkitekturen. Den inflexibla hårdvaran tvingar fram det ”bottom-up-” tillvägagångssätt som definieras av switchleverantörer när det gäller att beskriva nätverket och begränsar de möjligheter som erbjuds operatörerna för att styra och innovera i sina nät. För att möta kraven på att skapa en högre grad av flexibilitet för att designa, testa och garantera en snabbare tid till marknaden, introducerades begreppet Softly Defined Networks. Tanken, utöver att erbjuda de konventionella fördelarna med Software Defined Networking, bygger på att man implementerar ett omprogrammerbart dataplan. Field-Programmable Gate Arrays erbjuder en högre grad av flexibilitet och förmåga att hantera sådana konstruktioner. Programming Protocol-independent Packet Processors(P4) är ett språk på hög nivå som kontinuerligt utvecklas för att definiera dataplanet för olika nätverksenheter. Målet med P4 är att nätverksoperatörerna lätt ska kunna anpassa den underliggande hårdvaran med minimala begränsningar oberoende av leverantör av hårdvara. De tre huvudmålen när man definierade ett sådant språk handlade om omkonfigurerbarhet av hårdvaran efter att ha blivit utplacerad, protokolloberoende för att möjliggöra anpassning utan begränsningar och leverantörsoberoende för att användarna skulle vara mindre oroade över den underliggande hårdvaran. Nya framsteg i P4 när det gäller stöd för kompatibla hårdvaror och kompilatorer har gjort P4 till en tänkbar kandidat för att realisera en omprogrammerbar hårdvara. Detta arbete bidrar till att utforska hur enkelt det är att integrera P4:s förmåga att realisera ett flexibelt dataplan. För att uppnå detta och studera dess egenskaper föreslås en hårdvaruimplementation av L2 i två pipelines av P4 på en Kintex 7 FPGA. I första hand definieras en anpassad P4-modul som kan utföra L2-operationer på en dubbeltaggad Ethernet-ram med hjälp av en lämplig arkitekturmodell. Därefter implementeras P4-beskrivningen av hårdvaran på den föreslagna arkitekturmodellen med en hastighet av 10 Gbps med hjälp av de byggblock som krävs för att kunna observera beteendet. Med hjälp av en testupptällning testas konstruktionen för att se om den uppfyller den förväntade dataplanaktiviteten baserat på de uppsatta matchningsreglerna. När det gäller resursutnyttjandet förbrukar designen mindre än 15% av de tillgängliga resurserna och uppnår en genomsnittlig latens på 5,71us. Förutom den enkla implementeringen, jämfört med en konventionell fix beskrivning av data-planet, är det viktigt att analysera kostnaden vid införandet av P4. Den slutliga konstruktionen studeras därför med avseende på resursutnyttjande och latens genom att öka komplexiteten i P4-definitionen med avseende på antalet rubriker, tabeller och skrivoperationer (H-T-W) för den antagna kompilatorn. När det gäller åtta ”headers”, tabeller och skrivoperationer (8H-8T-8W), är det en genomsnittlig latens på 8.01us och P4-beskrivningen ensam kräver 51536 LUTs, 77789 FFs och 118,5 BRAMs vad gäller resursutnyttjande. Slutligen diskuterar artikeln hur den föreslagna top-down-metoden är implementerad och hur den kan omdefiniera nätverket som vi känner till det.
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Hassan, Ali. "Particle swarm optimization for routing and wavelength assignment in next generation WDM networks." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/533.
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All-optical Wave Division Multiplexed (WDM) networking is a promising technology for long-haul backbone and large metropolitan optical networks in order to meet the non-diminishing bandwidth demands of future applications and services. Examples could include archival and recovery of data to/from Storage Area Networks (i.e. for banks), High bandwidth medical imaging (for remote operations), High Definition (HD) digital broadcast and streaming over the Internet, distributed orchestrated computing, and peak-demand short-term connectivity for Access Network providers and wireless network operators for backhaul surges. One desirable feature is fast and automatic provisioning. Connection (lightpath) provisioning in optically switched networks requires both route computation and a single wavelength to be assigned for the lightpath. This is called Routing and Wavelength Assignment (RWA). RWA can be classified as static RWA and dynamic RWA. Static RWA is an NP-hard (non-polynomial time hard) optimisation task. Dynamic RWA is even more challenging as connection requests arrive dynamically, on-the-fly and have random connection holding times. Traditionally, global-optimum mathematical search schemes like integer linear programming and graph colouring are used to find an optimal solution for NP-hard problems. However such schemes become unusable for connection provisioning in a dynamic environment, due to the computational complexity and time required to undertake the search. To perform dynamic provisioning, different heuristic and stochastic techniques are used. Particle Swarm Optimisation (PSO) is a population-based global optimisation scheme that belongs to the class of evolutionary search algorithms and has successfully been used to solve many NP-hard optimisation problems in both static and dynamic environments. In this thesis, a novel PSO based scheme is proposed to solve the static RWA case, which can achieve optimal/near-optimal solution. In order to reduce the risk of premature convergence of the swarm and to avoid selecting local optima, a search scheme is proposed to solve the static RWA, based on the position of swarm‘s global best particle and personal best position of each particle. To solve dynamic RWA problem, a PSO based scheme is proposed which can provision a connection within a fraction of a second. This feature is crucial to provisioning services like bandwidth on demand connectivity. To improve the convergence speed of the swarm towards an optimal/near-optimal solution, a novel chaotic factor is introduced into the PSO algorithm, i.e. CPSO, which helps the swarm reach a relatively good solution in fewer iterations. Experimental results for PSO/CPSO based dynamic RWA algorithms show that the proposed schemes perform better compared to other evolutionary techniques like genetic algorithms, ant colony optimization. This is both in terms of quality of solution and computation time. The proposed schemes also show significant improvements in blocking probability performance compared to traditional dynamic RWA schemes like SP-FF and SP-MU algorithms.
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Jouet, Simon. "Enhancing programmability for adaptive resource management in next generation data centre networks." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8535/.
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Recently, Data Centre (DC) infrastructures have been growing rapidly to support a wide range of emerging services, and provide the underlying connectivity and compute resources that facilitate the "*-as-a-Service" model. This has led to the deployment of a multitude of services multiplexed over few, very large-scale centralised infrastructures. In order to cope with the ebb and flow of users, services and traffic, infrastructures have been provisioned for peak-demand resulting in the average utilisation of resources to be low. This overprovisionning has been further motivated by the complexity in predicting traffic demands over diverse timescales and the stringent economic impact of outages. At the same time, the emergence of Software Defined Networking (SDN), is offering new means to monitor and manage the network infrastructure to address this underutilisation. This dissertation aims to show how measurement-based resource management can improve performance and resource utilisation by adaptively tuning the infrastructure to the changing operating conditions. To achieve this dynamicity, the infrastructure must be able to centrally monitor, notify and react based on the current operating state, from per-packet dynamics to longstanding traffic trends and topological changes. However, the management and orchestration abilities of current SDN realisations is too limiting and must evolve for next generation networks. The current focus has been on logically centralising the routing and forwarding decisions. However, in order to achieve the necessary fine-grained insight, the data plane of the individual device must be programmable to collect and disseminate the metrics of interest. The results of this work demonstrates that a logically centralised controller can dynamically collect and measure network operating metrics to subsequently compute and disseminate fine-tuned environment-specific settings. They show how this approach can prevent TCP throughput incast collapse and improve TCP performance by an order of magnitude for partition-aggregate traffic patterns. Futhermore, the paradigm is generalised to show the benefits for other services widely used in DCs such as, e.g, routing, telemetry, and security.
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Fennell, Brett Jamerson. "Simultaneous solder reflow and underfill cure in next generation flip chip assembly." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16681.
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Dunmore, Martin. "QoS provisioning in the next generation Internet : the role of the network edge." Thesis, Lancaster University, 2001. http://eprints.lancs.ac.uk/11949/.
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Cheng, Zhangkai Jason. "A next-generation electronic portal imaging device for simultaneous imaging and dosimetry in radiotherapy." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23508.
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The aim of this thesis is to develop a next-generation Electronic Portal Imaging Device (EPID) for simultaneous megavoltage imaging and dosimetry in radiotherapy. The results of this thesis include the identification of a clinically implementable pixel sensitivity correction technique for a water equivalent EPID. This is important for clinical translation of this new technology. The imaging performance of an existing water equivalent EPID prototype previously developed by our group has been measured and characterised for the first time. The zero-frequency detective quantum efficiency (DQE) was found to be ~3%, which is a factor of three better than standard clinical EPIDs, which are not water-equivalent. A new design is proposed for further gains in imaging performance based on an array of air-clad optical fibres, and a fabrication method based on extrusion and fibre drawing has been developed and evaluated. Using finite element modelling simulations, a novel method is investigated for enhancing light output from the plastic scintillator array EPID. This method is based on inserting a nano-structured layer at the scintillator-detector interface, to maximize light transmission through the boundary. Overall, the work presented in this thesis demonstrates the feasibility of a next-generation EPID for clinical radiotherapy, with enhanced performance compared to standard clinical EPIDs.
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Nichols, Ben. "Validating next generation sequencing for meiofaunal community analysis and interaction prediction." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6801/.
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Advances in DNA sequencing technologies, particularly the advent of next generation sequencing (NGS) platforms, have revolutionised the field of metagenomics and allowed great progress to be made in the way that microbial communities are analysed. However, the wealth of data now available thanks to these advancements has made the possibilities far more numerous than just the obvious applications, with a wide variety of novel and diverse studies conceivable. The technologies themselves have also created further areas for research as better methods of handling the, often overwhelming in quantity and misleading in content, data are sought. The analysis carried out in this thesis demonstrates the wide range of study possible stemming from two experiments involving the sequencing of meiofauna DNA. The first of these involves community analysis of marine benthic meiofauna with particular emphasis on diversity and distribution. The second experiment involves the sequencing of pooled nematode samples in order to investigate the effects of sample richness and species relatedness on the generation of chimeric reads in sequencing data. It is shown that the data generated from these two experiments can be used to help formulate an algorithm to simulate PCR and therefore assist the generation of realistic noisy NGS data. These data can, in turn, be used to generate a simulated in silico microbial community for analysis, the results of which reveal insights into the accuracy of chimera detection software and the reliability of metagenetic community analyses. Worryingly, these results suggest that findings from similar in vitro studies are not as reliable as originally perceived. The same experimental data may also be used to investigate interactions between meiofauna species based on the incidental presence of prey species highlighted from the sequencing of individual meiofauna organisms. It is shown that these data can be used to accurately predict a nematode’s feeding type without having to examine the organism directly. It is also shown that there is no correlation between this method of inferring interactions between species and other methods which have been used in the past. This suggests that the earlier methods are inadequate when used for the detection of feeding interactions.
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Erbing, Axel. "In pursuit of next generation photovoltaics : An electronic structure study of lead-free perovskite solar cells." Licentiate thesis, Stockholms universitet, Fysikum, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-181608.
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The recent development of perovskite-based solar cells have shown a remarkably fast increase in power conversion efficiency making them a promising low-cost alternative to conventional cells. The most successful class of materials however, the lead-halide perovskites, are held back due to toxicity and stability issues significantly limiting their use. Because of this, the investigation of new, lead-free, light-absorber materials as a replacement is an important step towards improved solar cells. The focus of this licentiate thesis is the study of bismuth-based materials and their photovoltaic properties through electronic structure calculations. Specifically, the cubic-phase AgBi2I7 under gradual substitution of either bromine or antimony is investigated using density functional theory under periodic boundary conditions. This enables calculations of the system's energy levels and band structure. Furthermore, the energy variance of the employed model of the system is sampled with respect to its level of ion disorder to obtain a better understanding of the distribution of ions within the crystal. The materials are found to have good optical properties but comparatively low efficiencies. The introduced substitutions allow fine-tuning of the system's band gap and is shown to increase the overall performance of the solar cells. In addition, spin-orbit coupling effects are demonstrated to be important when treating these bismuth-based systems. The crystal structure is found to have a significant preference for separating its silver ions and cation vacancies.
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Makarovič, Andrej Boštjan. "The evolution of EU communications law and next generation networks : the limits of legal flexibility." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8609.
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This thesis analyses the evolution of the EU legal regulatory framework for electronic communications in light of the changes in the law's technological and business environment, namely the shift to Next Generation Networks (NGN). Using systems theory as its central research method, the thesis explores communications law as a self-referential phenomenon which, despite its internal attempts to promote itself by means of responding to the changing environment, remains locked-in by its own autopoietic structures. This is demonstrated by the law's traditional focus on voice telephony as the essential communications service provided in the public interest. Whereas the idea of 'technological neutrality' has enabled the law to embrace new applied technologies such as VoIP, it could not move its attention away from its autopoietic concepts to NGN-related issues such as net neutrality. Even though legal concepts without reference to any particular technology are increasingly used in regulation, as is the case with competition law images of 'relevant markets' and 'market power', the shift to NGN only remains visible to the law on its 'internal screen'. This becomes evident when the implementation of new technologies fails to achieve the results implied by the legal system, namely effective competition among different access infrastructures. Systems theory keeps a distance from both neo-liberal ideas that ideologically reject regulation, as well as from the autopoiesis of the NRAs' and the Commission's harmonising efforts, which inevitably result in more legal rules. Whereas the 'efficiency' of NGN investments cannot be implied based on the mere absence of ex ante regulation, the expected further proliferation of regulation based on the law's autopoietic programmes, although more cognitively open than before, will not be able to take on board all (possibly desirable) solutions that are not foreseen by the EU legal framework.
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Schirmer, Melanie. "Algorithms for viral haplotype reconstruction and bacterial metagenomics : resolving fine-scale variation in next generation sequencing data." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5627/.
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The discovery of DNA has been one of the biggest catalysts in genomic research. Sequencing has enabled us to access the wealth of information encoded in DNA and has provided the basis for ground-breaking achievements such as the first complete human genome sequence. Furthermore, it has tremendously advanced our understanding of life-threatening genetic disorders and bacterial and viral infections. With the recent advent of next generation sequencing (NGS) technologies, sequencing became accessible to the majority of researchers and made metagenomic sequencing widely available. However, to realise its true potential, sophisticated and tailor-made bioinformatic programs are essential to translate the collected data into meaningful information. My thesis explored the potential of resolving fine-scale variation in NGS data. The identification and correction of artificial fine-scale variation in the form of biases and errors is imperative in order to draw valid conclusions. Furthermore, resolving natural fine-scale variation in the form of single nucleotide polymorphisms (SNPs) and closely related species or strains is critical for the development of effective treatments and the characterisation of diseases. In recent years, Illumina has emerged as the global market leader in DNA sequencing. However, biases and errors associated with this high-throughput sequencing technology are still poorly understood which has precluded the development of effective noise removal algorithms. In addition, many programs were not designed for Illumina data or metagenomic sequencing. Therefore, a better understanding of the idiosyncrasies encountered in Illumina data is essential and programs must be tested and benchmarked on realistic and reliable in silico data sets to reveal not only their true capacities but also their limitations. I conducted the largest in vivo study of Illumina error profiles in combination with state-of-the-art library preparation methods to date. For the first time, a direct connection between experimental design factors and systematic errors was established, providing detailed insight into the nature of Illumina errors. Further, I tested various error removal techniques and developed a sophisticated Illumina amplicon noise removal algorithm, enabling researchers to choose optimal processing strategies for their particular data sets. In addition, I devised several simulation tools that accurately reflect artificial and natural fine-scale variation. This includes a flexible and efficient read simulation program which is the only program that can directly reflect the impact of experimental design factors. Furthermore, I developed a program simulating the evolution of a virus into a quasi-species. These programs formed the basis for two comprehensive benchmarking studies that revealed the capacities and limitations of viral haplotype reconstruction programs and taxonomic classification programs, respectively. My work furthers our knowledge of Illumina sequencing errors and will facilitate more accurate and effective analyses of sequencing data sets.
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Lenhert, Lance Ronald. "The next generation: A look at where today's enterprise resource planning (ERP) systems came from and where technology is heading." CSUSB ScholarWorks, 2000. https://scholarworks.lib.csusb.edu/etd-project/1689.
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"Currently, the largest barrier to any given market usually involves capital. If a company does not have enough investment capital to start with, it could fail before it even gets started. However, there is a new component that affects some of the largest corporations in the world. The problem relates to being able to sustain current internal processing, as well as adapt and grow in new markets with higher volumes. There are systems out there today that claim to address these issues along with e-commerce and other electronic sharing of information."
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Sadiq, Muhammad. "Design and fabrication of lanthanum-doped Sn-Ag-Cu lead-free solder for next generation microelectronics applications in severe environment." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44762.
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Sn-Pb solder has long been used in the Electronics industry. But, due to its toxic nature and environmental effects, certain restrictions are made on its use and therefore many researchers are looking to replace it. Sn-3.0Ag-0.5Cu (SAC) solders are suggested as lead-free replacements but their coarse microstructure and formation of hard and brittle Inter-Metallic Compounds (IMCs) like Ag₃Sn and Cu₆Sn₅ have limited their use in high temperature applications. In this research work, RE elements, mostly lanthanum (La), are used as potential additives to SAC alloys. They reduce the surface free energy, refine the grain size and improve the mechanical and wetting properties of SAC alloys. An extensive experimental work has been performed on the microstructure evolution, bulk mechanical properties, individual phase (matrix and IMCs) mechanical properties, creep behavior and wettability performance of the SAC and SAC-La alloys, with different (La) doping. SEM and EDS have been used to follow the continuous growth of the IMCs at 150°C and 200°C and thus provide a quantitative measure in terms of their size, spacing and volume fraction. Grain size is measured at regular intervals starting from 10 hours up to 200 hours of thermal aging using Optical Microscope with cross polarized light. Bulk mechanical properties are evaluated using tensile tests at low strain rates. Individual phase mechanical properties like Young's modulus, hardness, strain rate sensitivity index and bulge effects are characterized with nanoindentation from 100 µN up to 5000 µN loadings at different temperatures of 25°C, 45°C, 65°C and 85°C. Creep experiments are performed at elevated temperatures with good fitting of Dorn creep and back-stress creep models. Activation energy measurements are made at 40°C, 80°C and 120°C. Wettability testing on copper substrates is used for surface tension, wetting force and contact angle measurements of SAC and SAC-La doped alloys at 250°C and 260°C.
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Hassanzadeh, Reza. "A secure framework and related protocols for ubiquitous access to electronic health records using Java sim cards." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/37589/1/Reza_Hassanzadeh_Thesis.pdf.
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Ubiquitous access to patient medical records is an important aspect of caring for patient safety. Unavailability of sufficient medical information at the point-ofcare could possibly lead to a fatality. The U.S. Institute of Medicine has reported that between 44,000 and 98,000 people die each year due to medical errors, such as incorrect medication dosages, due to poor legibility in manual records, or delays in consolidating needed information to discern the proper intervention. In this research we propose employing emergent technologies such as Java SIM Cards (JSC), Smart Phones (SP), Next Generation Networks (NGN), Near Field Communications (NFC), Public Key Infrastructure (PKI), and Biometric Identification to develop a secure framework and related protocols for ubiquitous access to Electronic Health Records (EHR). A partial EHR contained within a JSC can be used at the point-of-care in order to help quick diagnosis of a patient’s problems. The full EHR can be accessed from an Electronic Health Records Centre (EHRC) when time and network availability permit. Moreover, this framework and related protocols enable patients to give their explicit consent to a doctor to access their personal medical data, by using their Smart Phone, when the doctor needs to see or update the patient’s medical information during an examination. Also our proposed solution would give the power to patients to modify the Access Control List (ACL) related to their EHRs and view their EHRs through their Smart Phone. Currently, very limited research has been done on using JSCs and similar technologies as a portable repository of EHRs or on the specific security issues that are likely to arise when JSCs are used with ubiquitous access to EHRs. Previous research is concerned with using Medicare cards, a kind of Smart Card, as a repository of medical information at the patient point-of-care. However, this imposes some limitations on the patient’s emergency medical care, including the inability to detect the patient’s location, to call and send information to an emergency room automatically, and to interact with the patient in order to get consent. The aim of our framework and related protocols is to overcome these limitations by taking advantage of the SIM card and the technologies mentioned above. Briefly, our framework and related protocols will offer the full benefits of accessing an up-to-date, precise, and comprehensive medical history of a patient, whilst its mobility will provide ubiquitous access to medical and patient information everywhere it is needed. The objective of our framework and related protocols is to automate interactions between patients, healthcare providers and insurance organisations, increase patient safety, improve quality of care, and reduce the costs.
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Voegele, Catherine. "Development of an integrated Information Technology System for management of laboratory data and next-generation sequencing workflows within a cancer genomics research platform." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10095/document.
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L'objectif de mon travail de thèse était de développer des outils bio informatiques permettant d'améliorer la traditionnelle gestion de l'information scientifique au sein d'un grand centre de recherche et en particulier au sein d'une plateforme de génomique. Trois outils ont été développés: un cahier de laboratoire électronique, un système de gestion de l'information de laboratoire pour des applications de génomique dont le séquençage de nouvelle génération, ainsi qu'un système de gestion des échantillons pour de grandes bio-banques. Ce travail a été réalisé en étroite collaboration avec des biologistes, épidémiologistes et informaticiens. Il a également inclus la mise en place d'interactions entre les différents outils pour former un système informatique intégré. Les trois outils ont été rapidement adoptés par l'ensemble des scientifiques du centre de recherche et sont désormais utilisés au quotidien pour le suivi de toutes les activités de laboratoire mais aussi plus globalement pour les autres activités scientifiques du centre de recherche. Ces outils sont transposables dans d'autres instituts de rechercheThe aim of my thesis work was to develop bioinformatics tools to improve the traditional scientific information management within a large research centre and especially within a genomics platform. Three tools have been developed: an electronic laboratory notebook, a laboratory information management system for genomics applications including next generation sequencing, as well as a sample management system for large biobanks. This work has been conducted in close collaboration with biologists, epidemiologists and IT specialists. It has also included the setup of interactions between the different tools to make an integrated IT system. The three tools have been rapidly adopted by all the scientists of the research centre and are now daily used for the tracking of all the laboratory’s activities but also more globally for the research centre’s other scientific activities. These tools are transposable in other research institutes
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Velardo, Amalia. "Small organic molecules for next generation electronics." Doctoral thesis, Universita degli studi di Salerno, 2016. http://hdl.handle.net/10556/2215.
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2014 - 2015In this PhD thesis attention has been focused on the theoretical design of organic small molecules for next generation electronics. The task of this thesis has concerned with the theoretical analysis of the operational performances of small dyes in photovoltaic solar cells, both in bulkheterojunction and dye sensitized solar cells; with particular emphasis on the theoretical analysis of the rates of the elementary electron transfer processes. A full quantum mechanics procedure for computing the rates of elementary electron transfer processes has been developed. The procedure starts from the Fermi Golden Rule (FGR) expression of the rate of electronic transitions and makes use of a rigorous evaluation of the Franck-Condon weighted density of states, performed by Kubo’s generating function approach. The analysis of electron transfer rates has revealed to be a very powerful tool for investigating structure-property relationships for the employment of small organic molecules in photovoltaic solar cells. The methodology has been applied to a class of small organic molecules, which show different power energy conversion efficiencies. The different efficiencies of the dyes have been attributed to very different rates of photoinduced electron transfer, the first step of energy conversion process in any type of photovoltaic solar cell. The last part of this thesis has been devoted to a very important task for next generation electronics: the rational design of new N-rich fused-ring heteroaromatics small organic molecules for n-type charge transport in thin layers. The substitution of CH units with nitrogen atoms is particularly appealing because, it offers the possibility of tuning the electron donor/acceptor character of the molecule. [edited by author]
XIV n.s.
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Dongxu, Yang. "Novel resists for next generation lithography." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6532/.
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With progress in the semiconductor industry, transistor density on a single computer chip has increased dramatically. This has resulted in a continuous shrinkage of the minimum feature size printed through microlithography technology. Resist, as the pattern recording medium of such printing, has been extensively studied to achieve higher resolution, higher sensitivity and lower line edge roughness. For decades this has been realized through chemical amplification. With the feature size continuously shrinking and the energy of exposure source therefore exceeding the resist ionization threshold, the performance of conventional chemically amplified resists is approaching the limits. Novel high-performance chemically amplified resists or non-chemically amplified resists are urgently needed to meet the requirement of next generation lithography. In this work a negative tone chemically amplified resist system based on a novel method to control the catalytic chain reaction is presented. The method to control the catalytic chain reaction is demonstrated using two model polymer resists. This method is then applied to a fullerene-based molecular resist system and a combination of good industrial compatibility, high resolution and good sensitivity has been achieved in this resist. Through a chromatographic separation, another chemically amplified molecular resist was also developed with further improved performance. An alternative route to sensitivity improvement other than chemical amplification is then introduced and a family of fullerene-based metal containing materials is presented. Lithographic performance is compared between the fullerene-metal resists and their control materials without metal. Using an aberration corrected scanning transmission electron microscope, the distribution of metal in the resist film and its behavior during the lithography process is evaluated and discussed.
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Jeon, Hyung Min. "Multifunctional Oxide Heterostructures For Next-Generation Tunable RF/Microwave Electronics." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1578950463103112.
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Manyam, Jedsada. "Novel resist materials for next generation lithography." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1333/.
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Fullerene derivatives have been demonstrated as negative-tone resists for electron beam lithography with impressive capability for high resolution and high plasma etching resistance, due to their carbon-rich nature. Their primary drawback of extremely poor sensitivity has been addressed by implementation of chemical amplification. A three-component chemically amplified negative-tone resist has been developed via the addition of a photoacid generator and a crosslinker to a fullerene derivative. This thesis work presents a significant extension of the previous work. The resists have undergone comprehensive optimisation, and systematic characterisation of electron beam lithography behaviours. In the first part, a systematic study into chemical amplification of negative-tone fullerene resists through variation of resist composition, additive, and resist processing in order to optimise sensitivity, resolution, line width roughness and etch resistance is presented. Sensitivity of sub 10 C/cm2 at 20 keV, half pitch resolution of 20 nm, a minimum sparse feature linewidth of 12 nm, line width roughness of sub 5 nm, and high etch resistance comparable with a commercial novolac resist have been demonstrated. The second part presents the development of a chemically amplified positive-tone fullerene based resists with the advantage of aqueous base solution development. Their lithographic capability is evaluated and discussed.
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Wang, Zhongnan. "Tribological investigation for next-generation polymeric micro-systems." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/91016/.
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The development of micro-fabrication processes for 3D microstructures has led to the production of low-cost, low-energy devices at millimeter scales known as MEMS for a wide range of electronic, mechanical, mechatronic and biomedical applications. As surface-to-volume ratio increases drastically with decreasing dimension, surface properties of the materials are the prominent factor at the interface between two solids and consequent tribological issues such as adhesion, friction and wear will arise in MEMS devices when surfaces are in, or have the potential for, sliding contact. Measurement techniques and principles used in micro-tribology are quite different from those in macro-tribology. Various specialized micro-tribometers have attracted recent attention in attempts to obtain consistent, accurate tribological measurements that could provide information for the design of MEMS components. However, even these have operational parameters quite different to those in the regime typical of MEMS devices. For example, the thermal properties of polymers might mean that they are especially sensitivity to the speeds and reciprocating scan frequencies of measurements. This is a serious concern because the selection of appropriate materials for such applications is very important in order to reduce not only friction and wear, but also the stiction of the parts. The immediate challenge is that there is very little reliable information about the properties of this new generation of engineering materials because of insufficient understanding and characterization of their behaviour at the microscale under a wide range of experimental conditions. With these points in mind, this thesis aims to prompt wide study of the micro-tribological properties of polymers for MEMS applications, providing preliminary new data on them while exploring in some detail possible uncertainty effects that could arise from the testing regimes of most micro-tribometers. It starts by re-commissioning and characterizing a unique, wide-bandwidth prototype micro-tribometer developed at Warwick, establishing good operating procedures by comparing measurements on materials widely discussed in the literature. New data has been collected on an acrylate resin typically used for micro-stereo-lithography, PTFE and oxide-coated silicon. It suggests that deviations from Amonton’s law in the ten millinewton range might be less severe than previously reported. Observing that the skill and time required for such testing makes it unattractive for a production control environment, the thesis then explores, via contact modelling, whether there is a useful correlation between Berkovich tip nano-hardness and the micro-friction of the polymeric samples: several plausible modelling assumptions are shown to lead to inconsistencies. Final discussions and recommendations consider how to move on from these experimental scoping studies to acquire detailed evaluations of the properties of the best candidates under typical usage conditions prior to designers of potential products taking these materials and processes at all seriously.
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Romeo, Lorenzo. "Semiconductor nanowires: the building block for next generation electronics and photonics." Doctoral thesis, Scuola Normale Superiore, 2016. http://hdl.handle.net/11384/86200.
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York, Jr John Benson. "An Isolated Micro-Converter for Next-Generation Photovoltaic Infrastructure." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19326.
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Photovoltaic (PV) systems are a rapidly growing segment in the renewable energy industry. Though they have humble origins and an uncertain future, the commercial viability of PV has significantly increased, especially in the past decade. In order to make PV useful, however, significant effort has to go into the power conditioning systems that take the low-voltage dc from the panel and create utility compatible ac output. Popular architectures for this process include the centralized inverter and the distributed micro-inverter, each with its own advantages and disadvantages. One attempt to retain the advantages of both architectures is to centralize the inverter function but construct PV panel-level micro-converters which optimize the panel output and condition the power for the inverter. The main focus of this work is to explore the technical challenges that face the evolution of the dc-dc micro-converter and to use them as a template for a vertically integrated design procedure. The individual chapters focus on different levels of the process: topology, modulation and control, transient mitigation, and steady-state optimization. Chapter 2 introduces a new dc-dc topology, the Integrated Boost Resonant (IBR) converter, born out of the natural design requirements for the micro-converter, such as high CEC efficiency, simple structure, and inherent Galvanic isolation. The circuit is a combination of a traditional PWM boost converter and a discontinuous conduction mode (DCM), series resonant circuit. The DCM operation of the high-frequency transformer possesses much lower circulating energy when compared to the traditional CCM behavior. When combined with zero-current-switching (ZCS) for the output diode, it results in a circuit with a high weighted efficiency of 96.8%. Chapter 3 improves upon that topology by adding an optimized modulation scheme to the control strategy. This improves the power stage efficiency at nominal input and enhances the available operating range. The new, hybrid-frequency method utilizes areas where the modulator operates in constant-on, constant-off, and fixed-frequency conditions depending on duty cycle, the resonant period length, and the desired input range. The method extends the operating range as wide as 12-48V and improves the CEC efficiency to 97.2% in the 250-W prototype. Chapter 4 considers the soft-start of the proposed system, which can have a very large capacitive load from the inverter. A new capacitor-transient limited (CTL) soft-start method senses the ac transient across the resonant capacitor, prematurely ending the lower switch on-time in order to prevent an excessive current spike. A prototype design is then applied to the IBR system, allowing safe system startup with a range of capacitive loads from 2μF to 500μF and a consistent peak current without the need for current sensing. Chapter 5 further investigates the impact of voltage ripple on the PV output power. A new method for analyzing the maximum power point tracking (MPPT) efficiency is proposed based on panel-derived models. From the panel model, an expression demonstrating the MPPT efficiency is derived, along with a ripple â "budgetâ " for the harmonic sources. These ripple sources are then analyzed and suggestions for controlling their contributions are proposed that enable circuit designers to make informed and cost-effective design decisions. Chapter 6 illustrates how results from a previous iteration can provide a basis for the next generation\'s design. A zero-voltage-switching (ZVS) version of the circuit in Chapter 2 is proposed, requiring only two additional MOSFETs and one inductor on the low-voltage side. The maximum switching frequency is then increased from 70kHz to 170kHz, allowing for a 46% reduction in converter volume (from 430cm3 to 230cm3) while retaining greater than 97% weighted efficiency.
Ph. D.
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Hegarty, Declan. "FPGA-based architectures for next generation communications networks." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/455/.
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This engineering doctorate concerns the application of Field Programmable Gate Array (FPGA) technology to some of the challenges faced in the design of next generation communications networks. The growth and convergence of such networks has fuelled demand for higher bandwidth systems, and a requirement to support a diverse range of payloads across the network span. The research which follows focuses on the development of FPGA-based architectures for two important paradigms in contemporary networking - Forward Error Correction and Packet Classification. The work seeks to combine analysis of the underlying algorithms and mathematical techniques which drive these applications, with an informed approach to the design of efficient FPGA-based circuits.
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Simpson, Robert E. "Chalcogenide thin film materials for next generation data storage." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/52041/.
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Data can be stored in the form of amorphous and crystalline marks within a chalcogenide thin film. Commonly Ge. Therefore Ga:La:S:Cu shows potential as a future electrical phase change data storage material.
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Culverhouse, Philip Frederick. "A specification for a next generation CAD toolkit for electronics product design." Thesis, University of Plymouth, 1993. http://hdl.handle.net/10026.1/2648.
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Electronic engineering product design is a complex process which has enjoyed an increasing provision of computer based tools since the early 1980's. Over this period computer aided design tool development has progressed at such a pace that new features and functions have tended to be market driven. As such CAD tools have not been developed through the recommended practise of defining a functional specification prior to any software code generation. This thesis defines a new functional specification for next generation CAD tools to support the electronics product design process. It is synthesized from a review of the use of computers in the electronics product design process, from a case study of Best Practices prevalent in a wide range of electronics companies and from a new model of the design process. The model and the best practices have given rise to a new concept for company engineering documentation, the Product Book which provides a logical framework for constraining CAD tools and their users (designers) as means of controlling costs in the design process. This specification differs from current perceptions of computer functionality in the CAD tool industry by addressing human needs together with company needs of computer supported design, rather than just providing more technological support for the designer in isolation.
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Kgwadi, Monageng. "Low-cost antennas and systems for next generation wireless communications." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8396/.
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This work presents a study of low-cost antennas and communication systems to support the burgeoning demand for bandwidth in the next generation wireless communications and networks (5G) and/or Internet of Things (IoT). The work was divided into three different fields all aimed at low-cost solutions of enabling next generation networks (5G) and IoT. The first part of the study involves study of low-cost fabrication of antennas and radio frequency (RF) guided wave structures up to 10 GHz using the thermal transfer printing (TTP) technique on renewable, light weight, flexible and low-cost substrates. The thermal transfer printing method for electronics was characterised from DC to 10 GHz and benchmarked for performance against inkjet printing technique which is an established technique for printed electronics. TTP achieved similar or better read range to inkjet printed radio frequency identification (RFID) antennas that were used in this study. Applications of the TTP method in IoT taking advantage of its speed and low cost were demonstrated by; producing on-demand antennas and/or rapid prototyping electronic designs, using off the shelf components to build a frequency agile antenna, and an ultra wideband antenna (UWB) for low power short range communications. The second part involves design and optimisation of a multi-port driven (MPD) slot-ring antenna for purposes of integration with resonant tunnelling diode (RTD) oscillators for millimetre-wave communications. The optimised structure managed airside radiation without the use of bulky lenses and achieved directivity of 10.8 dBi. The concept of the slot-ring with a backing ground plane was experimentally verified by a fabricated antenna for 5 GHz operation showing the expected performance. The third part is an experimental study of modulating RTD oscillators to deter- mine and improve achievable modulation bandwidth to meet 5G demands. Wireless transceiver systems at 28-40 GHz and 240 GHz were build using combinations of horn antennas, quasi-optical Schottky barrier diode detectors and some off-line signal processing. The modulation bandwidth of the oscillators were found to be limited to 300 Mbps and 16 Mbps for the 28-40 GHz oscillators and 220-300 GHz oscillators respectively due to oscillators being optimised for high power output instead of high modulation rates. Recommendations are made to improve the modulation datarate of these oscillators in order to meet the 5G datarate targets.
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Churm, James. "Design and fabrication of a next generation regenerative neural interface." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8198/.
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A Spiral Peripheral Neural Interface (SPNI) is an electrode array that has been previously presented as a regenerative neural interface capable of receiving information from, and transmitting information to nerves. The SPNI has previously been proven in concept, however, when stimulating nerves in the device, the electrodes areinsufficiently isolated from each other and stimulations can trigger unwanted neural activity in neighbouring channels of the SPNI. Along with this, neural interfaces generally, suffer from chronic viability problems, due to biological rejection. These issues were addressed in this thesis, by the addition of a PDMS silicone membrane, into the structure of the SPNI. Improvements to the understanding and performance of structural, electrical and biocompatibility aspects of the SPNI are addressed, with the addition of the PDMS film, which is used to electrically seal SPNI channels whilst not hindering conductor integrity. The inclusion ofPDMS also provides a platform which may enable drug delivery. This work dramatically improves SPNI performance whilst providing routes to improved biocompatibility. This thesis addresses the main issues previously presented in the SPNI and brings the device up to a new standard which can once again be tested for its viability in vivo.
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Chapagain, Kamal Raj. "Integration of Electronics and Mechanics in Next Generation Ultrasound Transducers in Medical Imaging." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24325.
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Capacitive micromachined ultrasonic transducer (CMUT) has been emerging technology in the field of medical imaging after its first demonstration in early 90s. CMUTs are fabricated on silicon substrates using micromachining techniques. They can generate high frequencies due to the smaller dimensions feasible with microfabrication. CMUTs for immersion applications could be easily designed to provide fractional bandwidths exceeding 100%. Therefore, they are promising for applications like intravascular ultrasound (IVUS) where high resolution is required at short range. In this domain it may perform better than the existing piezoelectric ultrasound transducers. But there are certain issues that need to be taken care of before they can be used as commercial ultrasound transducers. One is echoes due to the acoustic wave propagation in the silicon substrate, and another is resonances caused by cross coupling between the neighboring elements in the CMUT arrays. In this thesis we investigate an acoustic backing structure that is to be added on the back side of the CMUT. The backing should absorb incident acoustic waves across a wide frequency band, and it must effectively suppress structural resonances and vibrations. To achieve this, the backing of a CMUT should have an acoustic impedance that matches with the silicon substrate, and it should be lossy. A good candidate for the backing is a tungsten filled epoxy. If the backing structure is thick enough, it will absorb the acoustic wave reflected back to the transducer and thus will remove any trailing echoes. In many cases the transducer is intended for applications where there is little room for a thick backing. Various approaches has been suggested to reduce the extra volume and weight added by a thick absorbing backing, one approach is to use a grooved backing structure. The grooves at the bottom of the backing provide an extra attenuation by scattering the waves in different directions so that a thinner backing would be sufficient. The scattering removes power from the specular reflection from the back surface which otherwise degrades the image quality. It has been shown that this type of structure reduces the specular reflection for a range of frequencies. When CMUTs are used in practical applications, the propagation of waves from a fluid medium into the backing or vice versa is blocked to some degree by total reflection, except for a range of steering angles around broadside. This is due to the difference in acoustic velocities of silicon and the fluid medium. This blocking is accompanied by the generation of surface waves in the silicon substrate, which also may impact the imaging and therefore must be controlled. In the present work we investigate the acoustic signal transmitted into the backing relative to the signal transmitted into the fluid medium when CMUT arrays on top of the silicon substrate are excited. This gives us an estimation of how much attenuation is needed from the acoustic backing layer. The purpose of the grooves on the backing structure is to provide an attenuation due to scattering which is in addition to the absorption loss in the epoxy tungsten composite. Experiments performed on the grooved backing structures show that such structures provide a satisfactory performance for the waves traveling normal to the bottom of the backing structure. But the acoustic waves propagating into the backing structure may not always be normal to the bottom of the structure. Therefore, the performance of the grooved backing structure is also studied for the waves traveling in oblique directions to the bottom surface of the backing. From our simulations we know that the performance of grooved structures for oblique incidence is not significantly different from that of normal incidence when the incident angle is within ±30◦ to the surface normal to the bottom of the structure. We have also shown that for a CMUT-backing stack immersed in a fluid medium, waves that reach into the backing from the fluid medium with significant power mostly lie within this range of angles. It means that a CMUT transducer with grooved backing structure always provide extra attenuation for the waves propagating into the substrates when it is used in practical applications. In this work we have also investigated acoustic properties of some polymers. The polymers, RTV 615 and Sylgard 160, have acoustic properties such that a thin layer of these polymers could be used to minimize the acoustic cross coupling in the CMUT arrays significantly. These materials could also be used as lens material for CMUT transducers together with stiff polymers such as TPX.
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Al, Sayeed Choudhury Abdullah. "Characterization and experimental validation of reconfigurable optical adddrop multiplexers for next generation network." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27218.
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This thesis proposes a detailed design layout for the next generation optical metropolitan network to be equipped with Reconfigurable Optical Add/Drop Multiplexer (ROADM) subsystems. It demonstrates the key features of ROADM subsystems including the development of ring-to-ring interconnection in optical domain.
Simulation models are developed for the ROADM subsystems that can easily be configured according to the devices' available specification sheet. The developed simulation models have been verified with experimental measurements obtained from a reconfigurable all-optical metro network testbed. Such simulation modules will be valuable in planning and designing the next generation metro optical networks.
Combining the outcome of the research results presented in the thesis, a hybrid reconfigurable add/drop module is proposed. The proposed hybrid architecture can achieve lower loss among the existing 3rd generation ROADM modules. The functionality of ROADMs can also be improved by an Intelligent ROADM subsystem proposed for the next generation dynamically provisioned wavelength network.
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Garcia, Hernandez Juan Camilo. "Development of a Class D motor amplifier for a next-generation mechanism control electronics." Thesis, Luleå tekniska universitet, Rymdteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60411.
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This thesis was written at Airbus DS GmbH in Friedrichshafen, Germany, as part of a project which aims to develop a new generation of class-D power amplification circuits for sinusoidal commutating motors controlling the movement of different mechanisms in satellites. Currently used topologies have disadvantages such as high power loss, analog controlling and high degree of signal distortion. This work first simulates available topologies which were previously developed by the company in order to compare them and build a trade-off list so the most suitable circuit is selected. Then, by further simulating and analysis several improvements to the circuit are suggested and a final schematic is developed including an analogue-to-digital converter and a total of three phases to power a motor. After a demonstrator circuit was designed and built, it was tested by using an external real time target machine to generate the corresponding PWM signals in correspondence to a controlling signal generated via Simulink. The final product of this thesis confirmed the simulation results such as an improved signal quality at higher frequencies in comparison to an available measurement from a previous generation circuit. The flexibility of the topology as well as the possibility of implementing a digital control was also confirmed during this phase of the project. Upon further work, the dimensioning of the output low pass filter should be improved and a digital PID controller should be implemented in the controlling FPGA. NOTE: This version of the Master Thesis deviates from the formal original submitted for examination in order not to disclose confidential information of Airbus DS GmbH. All positions in the document, where additional information was removed are properly identified. This document can be published according to the general rules of the Julius-Maximilians-Universität Würzburg and the Lulea University of Technology.This version of the Master Thesis deviates from the formal original submitted for examination in order not to disclose confidential information of Airbus DS GmbH. All positions in the document, where additional information was removed are properly identified. This document can be published according to the general rules of the Julius-Maximilians-Universität Würzburg and the Lulea University of Technology.
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Yu, Yiwei. "MIMO block spread OFDMA system for next generation mobile communications." Access electronically, 2008. http://ro.uow.edu.au/theses/109.
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Banerjee, Archan. "Optimisation of superconducting thin film growth for next generation superconducting detector applications." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8573/.
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There is a growing demand for superconducting detectors with single photon sensitivity from near- to far infrared wavelengths. Emerging application areas include imaging, remote sensing, astronomy and free space communications. Two superconducting device technologies, superconducting nanowire single-photon detectors (SSPDs/SNSPDs) and microwave kinetic inductance detectors (MKIDs) have the potential to outperform off-the-self semiconductor technologies and offer scalability to large arrays. Fabrication of high efficiency superconducting detectors strongly depends on the quality of superconducting thin films. The original work presented in this thesis has explored the growth and optimization of several superconducting thin film materials for next generation superconducting detectors. Films have been grown in an ultra-high vacuum sputter deposition system and an atomic layer deposition system. Since its initial demonstration, NbN and NbTiN have been predominantly used as the base material for SNSPDs. In this work, we have explored the optimization of both the materials with an emphasis on NbTiN. NbTiN is optimized by heating the substrates to 800 ̊C achieving a Tc of 10.4 K for a film thickness of 5.5 nm on silicon substrate. Due to their crystalline nature superconducting properties of NbN or NbTiN thin films are strongly correlated with the lattice parameters of substrate properties. This causes a restriction on the substrate choice and integration of SNSPD devices with complex circuits. Amorphous superconducting materials can be promising alternatives for this purpose. We have explored growth and optimization of amorphous MoSi and MoGe thin films. Both the materials are co-sputtered to tune the composition. For 5 nm thick MoSi film on silicon substrate we obtain Tc of 5.5 K. For MKID fabrication, TiN can be an useful base material due to its high sheet resistance and widely tuneable superconducting properties. TiN thin films have been sputtered on heated (500 ̊C) silicon substrates with a Tc of 3.9 K for a 90 nm thick film. The dielectric constants of the thin films as a function of wavelength (270-2200 nm) have been determined via variable angle spectroscopic ellipsometry (VASE). Atomic structure and stoichiometry of the films have been characterized in high resolution transmission electron microscopy (HRTEM). This study enables us to precisely control film properties and thus tailor superconducting films to the requirements of specific photon-counting applications.
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Davidson, Jonathan. "Advanced thermal modelling and management techniques to improve power density in next generation power electronics." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/8419/.
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This thesis sets out a series of new techniques to improve the thermal management of power electronics. The work is motivated by the increasing impetus to design smaller, more energy efficient electronic power systems for a range of applications, notably electric vehicles. Thermal management is an increasingly important tool which can facilitate improvements in power density through better monitoring and control of system temperatures. This thesis seeks to deliver improvements in implementing this strategy. A review of the state of the art in thermal management is reported, focussing on temperature measurement, thermal characterisation and system modelling techniques. In addition, novel techniques for arbitrary dissipation control and die temperature measurements in semiconductor devices are presented. A novel analysis of the limitations of low-order thermal models is also described. Improvements and applications of these techniques form the basis of this thesis. The pseudorandom binary sequence (PRBS) technique for system identification is applied throughout the thesis to characterise thermal systems. A mathematical analysis is provided, together with a novel technique to determine the minimum gain which can be identified by PRBS techniques in the presence of noise. A novel improvement to the PRBS technique for typically ten times more noise resilient measurements is then developed based on mathematical mixing of different frequency PRBS signals. In parallel, a novel technique is formulated to estimate the temperature throughout a multiple device system using digital IIR filters and PRBS thermal characterisation, which achieves errors of 3-5% when demonstrated practically. By combining these techniques, a comprehensive temperature estimation and control methodology is implemented for a multiple device system under active cooling. Finally, the expansion of the proposed methodologies to steady-state die temperature estimation is presented with comparable accuracy to surface temperature measurements, increasing the usefulness of the developed techniques in a practical setting.
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Al-hussiany, Yahya Ali Lafta. "Novel DWT-DAPSK based transceivers for DVB-T transmission and next generation mobile networks." Thesis, Liverpool John Moores University, 2012. http://researchonline.ljmu.ac.uk/6168/.
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Digital wireless communication has become one of the most exciting research topics in the electronic engineering field due to the explosive demands for high-speed wireless services, such as cellular video conferencing. The second generation Terrestrial Digital Video Broadcasting (DVB- T2) has been demonstrated to provide digital communication services with very high spectral efficiency and significantly improved performance. Orthogonal Frequency Division Multiplexing (OFDM) systems have been increasingly deployed in mobile networks for their spectral efficiency and optimum bit error rate. An OFDM system is a multi-carrier system which transmits signals from a single source at different frequencies simultaneously as parallel components. A distinguishing feature of the OFDM system is its ability to preserve high bandwidth efficiency in high speed data streams. Among the different types of OFDM systems, wavelet based systems have been demonstrated to have much better bandwidth and channel performance compared to the Discrete Fourier transform (DFT) and Discrete Cosine Transform (DCT) based systems. The DFT and DCT systems suffer from several disadvantages including less bandwidth efficiency due 'to the need for guard interval and highly complex system design. Discrete Wavelet transform (DWT) based OFDM systems naturally overcome these disadvantages by their design methodology and the technique of transmitting concentrated energy over small spectral coefficients. Several types of modulation schemes such as DPSK, QAM are employed in OFDM systems, which introduce certain penalties such as increased bandwidth and complexity of the system design. So a multilevel differential modulation technique namely Differential Amplitude and Phase Shift Keying (64 DAPSK) has been proposed as an alternative solution. DAPSK-OFDM is very suitable for high date-rate digital mobile radio channel with additive white Gaussian noise (A WGN). In this research work it has been f demonstrated that a combination of DWT -OFDM with DAPSK modulation can be employed to achieve very low peak-to-average power ratio (PAPR), improved bit error ratio (BER), and much reduced inter symbol interference (ISI) & inter-carrier interference (IeI) in wireless mobile network applications. A mathematical model has been proposed for the DWT-OFDM system with DAPSK modulation scheme in this work. The system performance has been evaluated via simulation using Matlab Simulink package and also verified using Matlab programming. This proposed DWT-OFDM with 64DAPSK hybrid system is demonstrated to have better BER (by an order of magnitude for an SNR of 25dB) performance and improved P APR (by 7.2dB) and interference values. It is also demonstrated that including companding with this system results in further reduction of PAPR. Finally, the simulation results also demonstrate that DWT-DAPSK scheme can be successfully employed in DVTB-T2 systems due to its very high spectral efficiency, much improved BER and significantly reduced PAPR performance.
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Liu, Xiaotao. "CHARACTERIZATION OF NANOSTRUCTURE, MATERIALS, AND ELECTRON EMISSION PERFORMANCE OF NEXT-GENERATION THERMIONIC SCANDATE CATHODES." UKnowledge, 2019. https://uknowledge.uky.edu/cme_etds/96.
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Scandate cathodes, where scandia is added to the tungsten cathode pellets, have recently received substantial and renewed research interest owing to significantly improved electron emission capabilities at lower temperatures, as compared with conventional dispenser cathodes. However, there are several persistent issues including non-uniform electron emission, lack of understanding regarding scandium’s role in the emission mechanism, and unreliable reproducibility in terms of scandate cathode fabrication. As a result, scandate cathodes have not yet been widely implemented in actual vacuum electron devices (VEDs).
The surface structure and chemical composition of multiple scandate cathodes – prepared with the powder using the liquid-solid (L-S) technique – and exhibiting excellent emission behavior were characterized to give insight into the fundamental mechanism(s) of operation. This was achieved with high-resolution electron microscopy techniques that include high-precision specimen lift-out. These studies showed that the micron-sized tungsten particles that compose the largest fraction of the cathode body are highly faceted and decorated with nanoscale Ba/BaO (~10 nm), as well as larger (~150 nm) Sc2O3 and BaAl2O4 particles. The experimentally identified facets were confirmed through Wulff analysis of the tungsten crystal shape and were determined to consist of {110}, {100}, and {112} facets, in increasing order of surface area prevalence. Furthermore, it is estimated that Ba atoms decorating the tungsten crystal surfaces are present in quantities such that monolayer coverage is possible at elevated temperatures.
The high-resolution electron microscopy techniques used to investigate the cross section (near-surface) of the L-S scandate cathodes also revealed that the BaAl2O4 particles (100-500 nm) that attach to the larger tungsten particles are either adjacent to the smaller Sc2O3 nanoparticles or encompass them. Furthermore, high-resolution chemical analysis and 3D elemental tomography show that the two oxides always appear to be physically distinct from each other, despite their close proximity. 3D elemental tomography also showed that the Sc2O3 particles can sometimes appear inside the larger tungsten particles, but are inhomogeneously distributed. Nanobeam electron diffraction confirmed that the crystal structure of the tungsten particles are body-centered cubic, and imply that the structure remains unchanged despite the numerous complex chemical reactions that take place throughout the impregnation and activation procedures.
The role of Sc and the emission mechanism for scandate cathodes are discussed. Based on characterization results and materials computation, the role of Sc in scandate cathodes is possibly related to tuning the partial pressure of oxygen in order to establish an oxygen-poor atmosphere around the cathode surface, which is a necessary condition for the formation of the (near) equilibrium tungsten shape. A thin Ba-Sc-O surface layer (~8 nm) was detected near the surface of tungsten particles, using electron energy loss spectroscopy in the scanning transmission electron microscope. This stands in stark contrast to models invoking a ~100 nm Ba-Sc-O semiconducting surface layer, which are broadly discussed in the literature. These results provide new insights into understanding the emission mechanism of scandate cathodes.
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Pan, Bo. "Development of micromachined millimeter-wave modules for next-generation wireless transceiver front-ends." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24654.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: John Papapolymerou; Committee Chair: Manos Tentzeris; Committee Member: Gordon Stuber; Committee Member: John Cressler; Committee Member: John Z. Zhang; Committee Member: Joy Laskar
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Hontz, Michael Robert. "Next Generation Integrated Behavioral and Physics-based Modeling of Wide Bandgap Semiconductor Devices for Power Electronics." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1556718365514067.
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Bradley, Frank Mitchell. "Transport imaging for the study of quantum scattering phenomena in next generation Semiconductor devices /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Dec%5FBradley.pdf.
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Thetpraphi, Kritsadi. "Development of electroactive polymer actuators for next generation mirror : Live-Mirror." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI058.
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Nous avons développé une technologie nouvelle et interdisciplinaire pour créer des systèmes optiques à base de métamatériaux extrêmement légers, limités par la diffraction, avec une qualité optique exceptionnelle et un coût et un temps de production spectaculairement inférieurs : Live-Mirror. La nouveauté est de remplacer les miroirs optiques rigides et lourds classiques par des systèmes optoélectroniques dynamiques « vivants » et légers constitués d'une fine feuille de verre optique activement soutenue par plusieurs actionneurs / capteurs de force intégrés et miniaturisés via la fabrication additive et l'impression 3D. Nos fonctionnalités révolutionnaires Live-Mirror et le contrôle actif de la forme avec des actionneurs de force à plusieurs degrés de liberté obtenus en développant une technologie additive basée sur l'impression 3D pour appliquer un système optimisé de polymère électroactif (EAP) à un sandwich de surfaces de verre minces, ainsi créant un nouveau métamatériau hybride avec des propriétés de rapport rigidité / densité supérieures. Cette thèse décrit le développement d'actionneurs souples à base d'EAP modifiés / dopés, ici appelés terpolymère P (VDF-TrFE-CFE). Nous montrerons que cette nouvelle matrice de terpolymère personnalisée Live-Mirror présente une propriété de couplage électromécanique exceptionnelle, en particulier lorsqu'elle est dopée avec un plastifiant, par ex. phtalate de diisononyle (DINP). Ici, nous démontrons qu'en optimisant la conception multicouche structurée, le couplage électromécanique du terpolymère modifié peut être amélioré, offrant une permittivité diélectrique élevée, un module d'Young faible et une rigidité diélectrique exceptionnelle. Cela conduit à une réponse de déformation importante ainsi qu'à une densité d'énergie mécanique élevée sous des champs électriques relativement faibles selon le phénomène d'électrostriction - l'objectif principal des spécifications de haut niveau de Live-Mirror. En plus d'une matrice de terpolymère personnalisée, le concept de multicouches empilées est démontré comme une technique simple et efficace pour augmenter les capacités d'actionnement. Plusieurs résultats expérimentaux de preuve de concept imprimés en 3D (en laboratoire), qui sont en bon accord avec les modèles numériques, valident les performances de l'actionneur avec une grande réponse électromécanique. Cette technologie montre la faisabilité d'un contrôle actif de la forme de la surface optique et montre le contrôle et la correction de la forme optique Live-Mirror avec seulement quelques degrés de liberté. Une telle application d'actionneur novatrice et avancée via une technologie de fabrication additive est compatible avec les télescopes d'astronomie et de communication basés au sol et dans l'espace ainsi que de nombreux appareils électroniques modernesWe have developed new and interdisciplinary technology for creating extremely lightweight, diffraction-limited, meta-material-based optical systems with exceptional optical quality and spectacularly lower cost and production time: Live-Mirror. The novelty is to replace classical rigid and heavy optical mirrors with “live” and light dynamic optoelectronic systems consisting of a thin optical glass sheet actively supported by multiple force-actuators/sensors integrated and miniaturized via additive manufacturing and 3D printing. Our breakthrough Live-Mirror features and active shape control with many-degrees-of-freedom force actuators achieved by developing an additive 3D-printing-based technology to apply an optimized electroactive polymer (EAP) systems to a sandwich of thin glass surfaces, thus creating a novel hybrid meta-material with superior stiffness-to-density ratio properties. This thesis describes the development of soft actuators based on modified/doped EAPs, here dubbed terpolymer P(VDF-TrFE-CFE). We will show that this new and Live-Mirror customized terpolymer matrix features an outstanding electromechanical coupling property, particularly when doped with a plasticizer, e.g. diisononyl phthalate (DINP). Here we demonstrate that by optimizing the structured multilayer design, the electromechanical coupling of the modified terpolymer can be enhanced, yielding high dielectric permittivity, low Young modulus, and exceptional dielectric strength. This leads to a large strain response as well as high mechanical energy density under relatively low electric fields according to the electrostriction phenomenon – the main goal of the high-level specifications of Live-Mirror. In addition to a customized terpolymer matrix, the concept of stacked multilayers is demonstrated as a simple and effective technique to boost actuation abilities. Several 3D-printed, proof-of-concept (in the lab) experimental results, which are in good agreement with numerical models, validate the actuator performance with a large electromechanical response. This technology shows feasibility for active optical surface shape control and demonstrates the Live-Mirror optical shape control and correction with only a few degrees-of-freedoms. Such a novel and advanced actuator application via additive manufacturing technology are compliant for ground- and space-based astronomy and communications telescopes as well as many modern electronic devices
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Raleie, Naledi. "Chromium and Titanium based Stannum Nanocomposites materials as electron acceptors for next generation bulk Heterojunction photovoltaic cells." University of the Western Cape, 2018. http://hdl.handle.net/11394/6398.
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Philosophiae Doctor - PhD (Chemistry)Renewable energy has become the centrepiece of research in resolving the energy crisis. One of the forms of renewable energy is solar energy. This form of energy is costly to develop. Organic molecules are promising materials for the construction of next generation photovoltaic cells considering their advantage of lower cost compared to crystalline silicon that is currently used in solar cells. This forms the basis of this research, which focused on the synthesis and characterisation of poly(3- hexylthiophene) P3HT, stannum (Sn) nanoparticles and stannum-based bimetallic stannum-titanium (SnTi), stannum-chromium (SnCr) and stannum-vanadium (SnV) nanoparticles for the application in the construction of heterojunction photovoltaic cells (PVCs).
2021-12-31
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Han, Su-Mi. "Cyber counseling in the U.S.A. and South Korea : attitudes and needs of the millennial generation and the net generation on campus /." abstract and full text PDF (UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3294913.
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Thesis (Ph. D.)--University of Nevada, Reno, 2007."December, 2007." Includes bibliographical references (leaves 76-85). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Parsons, Robert Daniel. "Towards a measurement of the cosmic ray electron spectrum at the highest energies, using the next-generation Cherenkov Array CTA." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588755.
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The highly relativistic particles that arrive at the Earth, the long studied yet enigmatic cosmic rays, include >TeV electrons as well the dominant protons and nuclei. As during their diffusion in the interstellar medium these electrons undergo severe energy losses through both synchrotron and inverse Compton processes they are hence only able to travel relatively short distances. Therefore measurement of the spectrum of these electrons is able to give an important insight into the local distribution of cosmic ray sources. The use of IACTs to measure the highest energy electrons has already been pio- neered with the current generation of instruments such as HESS. This thesis describes the steps required to build upon these results and produce a measurement of the highest energy (>10 TeV) electrons, by use of the next generation ground-based gamma-ray telescope the Cherenkov Telescope Array. The first step in this process was the investigation of the systematic uncertainties in the modelling of high energy hadronic interactions and the resulting effect on the observable properties of the resulting air shower. This investigation was followed by the development of a new IACT event analysis chain, including improvements to both the event reconstruction and background rejection. The point source sensitivity of CTA candidate arrays could be increased up to 30% compared to the traditional chain. This chain was then applied to cosmic electrons and the sensitivity of CTA to electrons was determined. A simple semi-analytical model was then produced to demonstrate that signatures in the high energy electron spectrum from local sources are highly likely and should be observable with CTA at a high significance level
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Bandyopadhyay, Avra Sankar. "Light Matter Interactions in Two-Dimensional Semiconducting Tungsten Diselenide for Next Generation Quantum-Based Optoelectronic Devices." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1752376/.
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In this work, we explored one material from the broad family of 2D semiconductors, namely WSe2 to serve as an enabler for advanced, low-power, high-performance nanoelectronics and optoelectronic devices. A 2D WSe2 based field-effect-transistor (FET) was designed and fabricated using electron-beam lithography, that revealed an ultra-high mobility of ~ 625 cm2/V-s, with tunable charge transport behavior in the WSe2 channel, making it a promising candidate for high speed Si-based complimentary-metal-oxide-semiconductor (CMOS) technology. Furthermore, optoelectronic properties in 2D WSe2 based photodetectors and 2D WSe2/2D MoS2 based p-n junction diodes were also analyzed, where the photoresponsivity R and external quantum efficiency were exceptional. The monolayer WSe2 based photodetector, fabricated with Al metal contacts, showed a high R ~502 AW-1 under white light illumination. The EQE was also found to vary from 2.74×101 % - 4.02×103 % within the 400 nm -1100 nm spectral range of the tunable laser source. The interfacial metal-2D WSe2 junction characteristics, which promotes the use of such devices for end-use optoelectronics and quantum scale systems, were also studied and the interfacial stated density Dit in Al/2D WSe2 junction was computed to be the lowest reported to date ~ 3.45×1012 cm-2 eV-1.
We also examined the large exciton binding energy present in WSe2 through temperature-dependent Raman and photoluminescence spectroscopy, where localized exciton states perpetuated at 78 K that are gaining increasing attention for single photon emitters for quantum information processing. The exciton and phonon dynamics in 2D WSe2 were further analyzed to unveil other multi-body states besides localized excitons, such as trions whose population densities also evolved with temperature. The phonon lifetime, which is another interesting aspect of phonon dynamics, is calculated in 2D layered WSe2 using Raman spectroscopy for the first time and the influence of external stimuli such as temperature and laser power on the phonon behavior was also studied. Furthermore, we investigated the thermal properties in 2D WSe2 in a suspended architecture platform, and the thermal conductivity in suspended WSe2 was found to be ~ 1940 W/mK which was enhanced by ~ 4X when compared with substrate supported regions.
We also studied the use of halide-assisted low-pressure chemical vapor deposition (CVD) with NaCl to help to reduce the growth temperature to ∼750 °C, which is lower than the typical temperatures needed with conventional CVD for realizing 1L WSe2. The synthesis of monolayer WSe2 with high crystalline and optical quality using a halide assisted CVD method was successfully demonstrated where the role of substrate was deemed to play an important role to control the optical quality of the as-grown 2D WSe2. For example, the crystalline, optical and optoelectronics quality in CVD-grown monolayer WSe2 found to improve when sapphire was used as the substrate. Our work provides fundamental insights into the electronic, optoelectronic and quantum properties of WSe2 to pave the way for high-performance electronic, optoelectronic, and quantum-optoelectronic devices using scalable synthesis routes.