Springer Theses – serie

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3 146 produkter

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3 146 produkter

Second-Generation High-Temperature Superconducting Coils and Their Applications for Energy Storage
AvWeijia Yuan
Inbunden, Engelska, 2011
1 122 kr
Skickas inom 10-15 vardagar
Second-Generation High-Temperature Superconducting Coils and Their Applications for Energy Storage addresses the practical electric power applications of high-temperature superconductors. It validates the concept of a prototype energy storage system using newly available 2G HTS conductors by investigating the process of building a complete system from the initial design to the ﬁnal experiment. It begins with a clear introduction of the related background and then presents a comprehensive design of a superconducting energy storage system that can store maximum energy using a limited length of superconductors. The author has created a modeling environment for analysis of the system and also presents experimental results that are highly consistent with his theoretical calculations.
Multiscale and Multiphysics Computational Frameworks for Nano- and Bio-Systems
AvHyungjun Kim
Inbunden, Engelska, 2010
1 122 kr
Skickas inom 10-15 vardagar
This volume develops multiscale and multiphysics simulation methods to understand nano- and bio-systems by overcoming the limitations of time- and length-scales. Here the key issue is to extend current computational simulation methods to be useful for providing microscopic understanding of complex experimental systems. This thesis discusses the multiscale simulation approaches in nanoscale metal-insulator-metal junction, molecular memory, ionic transport in zeolite systems, dynamics of biomolecules such as lipids, and model lung system. Based on the cases discussed here, the author suggests various systematic strategies to overcome the limitations in time- and length-scales of the traditional monoscale approaches.
Discovery of Single Top Quark Production
AvDag Gillberg
Inbunden, Engelska, 2011
564 kr
Skickas inom 10-15 vardagar
The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking—the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies.Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years.This thesis presents the first discovery of single top quark production. It documents one of the flagship measurements of the D0 experiment, a collaboration of more than 600 physicists from around the world. It describes first observation of a physical process known as “single top quark production”, which had been sought for more than 10 years before its eventual discovery in 2009. Further, his thesis describes, in detail, the innovative approach Dr. Gillberg took to this analysis. Through the use of Boosted Decision Trees, a machine-learning technique, he observed the tiny single top signal within an otherwise overwhelming background. This Doctoral Thesis has been accepted by Simon Fraser University, Burnaby, BC, Canada.
Multistate GTPase Control Co-translational Protein Targeting
AvXin Zhang
Inbunden, Engelska, 2011
564 kr
Skickas inom 10-15 vardagar
Proteins act as macromolecular machinery that mediate many diverse biological processes - the molecular mechanisms of this machinery has fascinated biologists for decades. Analysis of the kinetic and thermodynamic features of these mechanisms could reveal unprecedented aspects of how the machinery function and will eventually lead to a novel understanding of various biological processes. This dissertation comprehensively demonstrates how two universally conserved guanosine triphosphatases in the signal recognition particle and its membrane receptor maintain the efficiency and fidelity of the co-translational protein targeting process essential to all cells. A series of quantitative experiments reveal that the highly ordered and coordinated conformational states of the machinery are the key to their regulatory function. This dissertation also offers a mechanistic view of another fascinating system in which multistate protein machinery closely control critical biological processes.Written while completing graduate work at California Institute of Technology.
Atomic Scale Characterization and First-Principles Studies of Si₃N₄ Interfaces
AvWeronika Walkosz
Inbunden, Engelska, 2011
1 122 kr
Skickas inom 10-15 vardagar
This thesis presents results from a combined atomic-resolution Z-contrast and annular bright-field imaging and electron energy loss spectroscopy in the Scanning Transmission Electron Microscopy, as well as first principles studies of the interfaces between crystalline β−Si3N4 and amorphous (i) CeO2-x as well as (ii) SiO2 intergranular film (IGF). These interfaces are of a great fundamental and technological interest because they play an important role in the microstructural evolution and mechanical properties of Si3N4 ceramics used in many high temperature and pressure applications. The main contribution of this work is its detailed description of the bonding characteristics of light atoms, in particular oxygen and nitrogen, at these interfaces, which has not been achieved before. The atomic-scale information on the arrangement of both light and heavy atoms is critical for realistic modeling of interface properties, such as interface strength and ion transport, and will facilitate increased control over the performance of ceramic and semiconductor materials for a wide-range of applications.
Search for Muon Neutrino to Electron Neutrino Oscillations in the MINOS Experiment
AvJuan Pedro Ochoa-Ricoux
Inbunden, Engelska, 2011
1 122 kr
Skickas inom 10-15 vardagar
The centerpiece of the thesis is the search for muon neutrino to electron neutrino oscillations which would indicate a non-zero mixing angle between the first and third neutrino generations (θ13), currently the “holy grail” of neutrino physics. The optimal extraction of the electron neutrino oscillation signal is based on the novel “library event matching” (LEM) method which Ochoa developed and implemented together with colleagues at Caltech and at Cambridge, which improves MINOS’ (Main Injector Neutrino Oscillator Search) reach for establishing an oscillation signal over any other method. LEM will now be the basis for MINOS’ final results, and will likely keep MINOS at the forefront of this field until it completes its data taking in 2011. Ochoa and his colleagues also developed the successful plan to run MINOS with a beam tuned for antineutrinos, to make a sensitive test of CPT symmetry by comparing the inter-generational mass splitting for neutrinos and antineutrinos. Ochoa’s in-depth, creative approach to the solution of a variety of complex experimental problems is an outstanding example for graduate students and longtime practitioners of experimental physics alike. Some of the most exciting results in this field to emerge in the near future may find their foundations in this thesis.
Quantum Phase Transitions in Cold Atoms and Low Temperature Solids
AvKaden Richard Alan Hazzard
Inbunden, Engelska, 2011
1 122 kr
Skickas inom 10-15 vardagar
The primary focus of this thesis is to theoretically describe nanokelvin experiments in cold atomic gases, which offer the potential to revolutionize our understanding of strongly correlated many-body systems. The thesis attacks major challenges of the field: it proposes and analyzes experimental protocols to create new and interesting states of matter and introduces theoretical techniques to describe probes of these states. The phenomena considered include the fractional quantum Hall effect, spectroscopy of strongly correlated states, and quantum criticality, among others. The thesis also clarifies experiments on disordered quantum solids, which display a variety of exotic phenomena and are candidates to exhibit so-called "supersolidity." It collects experimental results and constrains their interpretation through theoretical considerations.This Doctoral Thesis has been accepted by Cornell University, Ithaca, USA.
Characterization of Terahertz Emission from High Resistivity Fe-doped Bulk Ga0.69In0.31As Based Photoconducting Antennas
AvSuranjana Sengupta
Inbunden, Engelska, 2011
1 122 kr
Skickas inom 10-15 vardagar
Terahertz science and technology is attracting great interest due to its application in a wide array of fields made possible by the development of new and improved terahertz radiation sources and detectors. This book focuses on the development and characterization of one such source - namely the semi-large aperture photoconducting (PC) antenna fabricated on Fe-doped bulk Ga0.69In0.31As substrate. The high ultrafast carrier mobility, high resistivity, and subpicosecond carrier lifetime along with low bandgap make Ga0.69In0.31As an excellent candidate for PC antenna based THz emitter that can be photoexcited by compact Yb-based multiwatt laser systems for high power THz emission. The research is aimed at evaluating the impact of physical properties of a semi-large aperture Ga0.69In0.31As PC antenna upon its THz generation efficiency, and is motivated by the ultimate goal of developing a high-power terahertz radiation source for time-domain terahertz spectroscopy and imaging systems.
Topics in Theoretical and Computational Nanoscience
From Controlling Light at the Nanoscale to Calculating Quantum Effects with Classical Electrodynamics
AvJeffrey Michael McMahon
Inbunden, Engelska, 2011
1 122 kr
Skickas inom 10-15 vardagar
Interest in structures with nanometer-length features has significantly increased as experimental techniques for their fabrication have become possible. The study of phenomena in this area is termed nanoscience, and is a research focus of chemists, pure and applied physics, electrical engineers, and others. The reason for such a focus is the wide range of novel effects that exist at this scale, both of fundamental and practical interest, which often arise from the interaction between metallic nanostructures and light, and range from large electromagnetic field enhancements to extraordinary optical transmission of light through arrays of subwavelength holes.This dissertation is aimed at addressing some of the most fundamental and outstanding questions in nanoscience from a theoretical and computational perspective, specifically: · At the single nanoparticle level, how well do experimental and classical electrodynamics agree?· What is the detailed relationship between optical response and nanoparticle morphology, composition, and environment?· Does an optimal nanostructure exist for generating large electromagnetic field enhancements, and is there a fundamental limit to this? · Can nanostructures be used to control light, such as confining it, or causing fundamentally different scattering phenomena to interact, such as electromagnetic surface modes and diffraction effects?· Is it possible to calculate quantum effects using classical electrodynamics, and if so, how do they affect optical properties?
Muonium-antimuonium Oscillations in an Extended Minimal Supersymmetric Standard Model
AvBoyang Liu
Inbunden, Engelska, 2011
564 kr
Skickas inom 10-15 vardagar
This innovative work investigated two models where the muonium-antimuonium oscillation process was mediated by massive Majorana neutrinos and sneutrinos. First, we modified the Standard Model only by the inclusion of singlet right-handed neutrinos and allowing for general renormalizable interactions producing neutrino masses and mixing. The see-saw mechanism was employed to explain the smallness of the observed neutrino masses. A lower bound on the righthanded neutrino mass was constructed using the experimental limits set by the nonobservation of the muonium-antimuonium oscillation process. Second, we modified the Minimal Supersymmetric Standard Model by the inclusion of three right-handed neutrino superfields. The experimental result of the muonium-antimuonium oscillation process generated a lower bound on the ratio of the two Higgs field VEVs. This work helps to set up relationships between the experimental result of the muonium-antimuonium oscillation process and the model parameters in two specific models. Further improvement of the experiment in the future can generate more stringent bounds on the model parameters using the procedure developed by this work.
Power of Click Chemistry for Molecular Machines and Surface Patterning
AvJason M. Spruell
Inbunden, Engelska, 2011
1 122 kr
Skickas inom 10-15 vardagar
The union of covalent and noncovalent chemistries manifested in the mechanical bond represents one of the great chemical triumphs of the last half century. However, until recently, the preparation of mechanically interlocked compounds has often been an inefficient and limiting process. This thesis provides a detailed account of the great strides taken to increase the synthetic accessibility of donor-acceptor mechanically interlocked molecules by the application of highly efficient and ultra mild chemical transformations during their template-directed synthesis. These new departures in synthesis have indeed played a transformative role in that more complex, higher-order, and functional architectures – once only a dream – are now comfortably within reach. Specifically, the formation of mechanical bonds in higher order rotaxanes and catenanes has become ever easier through the use of highly efficient click chemistries. The resulting mechanically interlocked compounds are functional molecular media for a host of applications including information storage, mechanical actuation, and drug release.
Investigating the Nucleation, Growth, and Energy Levels of Organic Semiconductors for High Performance Plastic Electronics
AvAjay Virkar
Inbunden, Engelska, 2011
564 kr
Skickas inom 10-15 vardagar
This thesis details the significant progress made in improving the performance of organic transistors and the network conductivity of carbon nanotubes. The first section investigates organic semiconductor nucleation and growth on the most common dielectric surface used to fabricate organic thin film transistors. The nucleation and growth of the semiconductor was determined to be a critical factor affecting the device performance. Excellent dielectric modification layers, which promote desirable semiconductor growth leading to high conductivity were identified, and a technologically relevant deposition technique was developed to fabricate high quality dielectric modification layers over large areas. This may represent an important step towards the realization of large area organic circuity. In the final section, lessons learned from studying organic semiconductor nucleation and growth were utilized to improve the conductivity of carbon nanotube networks. Selective nucleation of materials at the junctions between nanotubes in the network significantly decreased the network's sheet resistance. The resulting networks may be promising candidates for transparent electrodes with a variety of optoelectronic applications.
Statistical Methods for Spoken Dialogue Management
AvBlaise Thomson
Inbunden, Engelska, 2013
1 155 kr
Skickas inom 10-15 vardagar
Speech is the most natural mode of communication and yet attempts to build systems which support robust habitable conversations between a human and a machine have so far had only limited success. A key reason is that current systems treat speech input as equivalent to a keyboard or mouse, and behaviour is controlled by predefined scripts that try to anticipate what the user will say and act accordingly. But speech recognisers make many errors and humans are not predictable; the result is systems which are difficult to design and fragile in use.Statistical methods for spoken dialogue management takes a radically different view. It treats dialogue as the problem of inferring a user's intentions based on what is said. The dialogue is modelled as a probabilistic network and the input speech acts are observations that provide evidence for performing Bayesian inference. The result is a system which is much more robust to speech recognition errors and for which a dialogue strategy can be learned automatically using reinforcement learning. The thesis describes both the architecture, the algorithms needed for fast real-time inference over very large networks, model parameter estimation and policy optimisation. This ground-breaking work will be of interest both to practitioners in spoken dialogue systems and to cognitive scientists interested in models of human behaviour.
Statistical Methods for Spoken Dialogue Management
AvBlaise Thomson
Häftad, Engelska, 2015
1 155 kr
Skickas inom 10-15 vardagar
Speech is the most natural mode of communication and yet attempts to build systems which support robust habitable conversations between a human and a machine have so far had only limited success. A key reason is that current systems treat speech input as equivalent to a keyboard or mouse, and behaviour is controlled by predefined scripts that try to anticipate what the user will say and act accordingly. But speech recognisers make many errors and humans are not predictable; the result is systems which are difficult to design and fragile in use.Statistical methods for spoken dialogue management takes a radically different view. It treats dialogue as the problem of inferring a user's intentions based on what is said. The dialogue is modelled as a probabilistic network and the input speech acts are observations that provide evidence for performing Bayesian inference. The result is a system which is much more robust to speech recognition errors and for which a dialogue strategy can be learned automatically using reinforcement learning. The thesis describes both the architecture, the algorithms needed for fast real-time inference over very large networks, model parameter estimation and policy optimisation. This ground-breaking work will be of interest both to practitioners in spoken dialogue systems and to cognitive scientists interested in models of human behaviour.
Second-Generation High-Temperature Superconducting Coils and Their Applications for Energy Storage
AvWeijia Yuan
Häftad, Engelska, 2016
1 122 kr
Skickas inom 10-15 vardagar
Second-Generation High-Temperature Superconducting Coils and Their Applications for Energy Storage addresses the practical electric power applications of high-temperature superconductors. It validates the concept of a prototype energy storage system using newly available 2G HTS conductors by investigating the process of building a complete system from the initial design to the ﬁnal experiment. It begins with a clear introduction of the related background and then presents a comprehensive design of a superconducting energy storage system that can store maximum energy using a limited length of superconductors. The author has created a modeling environment for analysis of the system and also presents experimental results that are highly consistent with his theoretical calculations.
Multiscale and Multiphysics Computational Frameworks for Nano- and Bio-Systems
AvHyungjun Kim
Häftad, Engelska, 2012
1 122 kr
Skickas inom 10-15 vardagar
This volume develops multiscale and multiphysics simulation methods to understand nano- and bio-systems by overcoming the limitations of time- and length-scales. Here the key issue is to extend current computational simulation methods to be useful for providing microscopic understanding of complex experimental systems. This thesis discusses the multiscale simulation approaches in nanoscale metal-insulator-metal junction, molecular memory, ionic transport in zeolite systems, dynamics of biomolecules such as lipids, and model lung system. Based on the cases discussed here, the author suggests various systematic strategies to overcome the limitations in time- and length-scales of the traditional monoscale approaches.
Discovery of Single Top Quark Production
AvDag Gillberg
Häftad, Engelska, 2014
564 kr
Skickas inom 10-15 vardagar
The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking—the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies.Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years.This thesis presents the first discovery of single top quark production. It documents one of the flagship measurements of the D0 experiment, a collaboration of more than 600 physicists from around the world. It describes first observation of a physical process known as “single top quark production”, which had been sought for more than 10 years before its eventual discovery in 2009. Further, his thesis describes, in detail, the innovative approach Dr. Gillberg took to this analysis. Through the use of Boosted Decision Trees, a machine-learning technique, he observed the tiny single top signal within an otherwise overwhelming background. This Doctoral Thesis has been accepted by Simon Fraser University, Burnaby, BC, Canada.
Muonium-antimuonium Oscillations in an Extended Minimal Supersymmetric Standard Model
AvBoyang Liu
Häftad, Engelska, 2014
564 kr
Skickas inom 10-15 vardagar
This innovative work investigated two models where the muonium-antimuonium oscillation process was mediated by massive Majorana neutrinos and sneutrinos. First, we modified the Standard Model only by the inclusion of singlet right-handed neutrinos and allowing for general renormalizable interactions producing neutrino masses and mixing. The see-saw mechanism was employed to explain the smallness of the observed neutrino masses. A lower bound on the righthanded neutrino mass was constructed using the experimental limits set by the nonobservation of the muonium-antimuonium oscillation process. Second, we modified the Minimal Supersymmetric Standard Model by the inclusion of three right-handed neutrino superfields. The experimental result of the muonium-antimuonium oscillation process generated a lower bound on the ratio of the two Higgs field VEVs. This work helps to set up relationships between the experimental result of the muonium-antimuonium oscillation process and the model parameters in two specific models. Further improvement of the experiment in the future can generate more stringent bounds on the model parameters using the procedure developed by this work.
Characterization of Terahertz Emission from High Resistivity Fe-doped Bulk Ga0.69In0.31As Based Photoconducting Antennas
AvSuranjana Sengupta
Häftad, Engelska, 2013
1 122 kr
Skickas inom 10-15 vardagar
Terahertz science and technology is attracting great interest due to its application in a wide array of fields made possible by the development of new and improved terahertz radiation sources and detectors. This book focuses on the development and characterization of one such source - namely the semi-large aperture photoconducting (PC) antenna fabricated on Fe-doped bulk Ga0.69In0.31As substrate. The high ultrafast carrier mobility, high resistivity, and subpicosecond carrier lifetime along with low bandgap make Ga0.69In0.31As an excellent candidate for PC antenna based THz emitter that can be photoexcited by compact Yb-based multiwatt laser systems for high power THz emission. The research is aimed at evaluating the impact of physical properties of a semi-large aperture Ga0.69In0.31As PC antenna upon its THz generation efficiency, and is motivated by the ultimate goal of developing a high-power terahertz radiation source for time-domain terahertz spectroscopy and imaging systems.
Atomic Scale Characterization and First-Principles Studies of Si₃N₄ Interfaces
AvWeronika Walkosz
Häftad, Engelska, 2013
1 122 kr
Skickas inom 10-15 vardagar
This thesis presents results from a combined atomic-resolution Z-contrast and annular bright-field imaging and electron energy loss spectroscopy in the Scanning Transmission Electron Microscopy, as well as first principles studies of the interfaces between crystalline β−Si3N4 and amorphous (i) CeO2-x as well as (ii) SiO2 intergranular film (IGF). These interfaces are of a great fundamental and technological interest because they play an important role in the microstructural evolution and mechanical properties of Si3N4 ceramics used in many high temperature and pressure applications. The main contribution of this work is its detailed description of the bonding characteristics of light atoms, in particular oxygen and nitrogen, at these interfaces, which has not been achieved before. The atomic-scale information on the arrangement of both light and heavy atoms is critical for realistic modeling of interface properties, such as interface strength and ion transport, and will facilitate increased control over the performance of ceramic and semiconductor materials for a wide-range of applications.
Search for Muon Neutrino to Electron Neutrino Oscillations in the MINOS Experiment
AvJuan Pedro Ochoa-Ricoux
Häftad, Engelska, 2013
1 122 kr
Skickas inom 10-15 vardagar
The centerpiece of the thesis is the search for muon neutrino to electron neutrino oscillations which would indicate a non-zero mixing angle between the first and third neutrino generations (θ13), currently the “holy grail” of neutrino physics. The optimal extraction of the electron neutrino oscillation signal is based on the novel “library event matching” (LEM) method which Ochoa developed and implemented together with colleagues at Caltech and at Cambridge, which improves MINOS’ (Main Injector Neutrino Oscillator Search) reach for establishing an oscillation signal over any other method. LEM will now be the basis for MINOS’ final results, and will likely keep MINOS at the forefront of this field until it completes its data taking in 2011. Ochoa and his colleagues also developed the successful plan to run MINOS with a beam tuned for antineutrinos, to make a sensitive test of CPT symmetry by comparing the inter-generational mass splitting for neutrinos and antineutrinos. Ochoa’s in-depth, creative approach to the solution of a variety of complex experimental problems is an outstanding example for graduate students and longtime practitioners of experimental physics alike. Some of the most exciting results in this field to emerge in the near future may find their foundations in this thesis.
Quantum Phase Transitions in Cold Atoms and Low Temperature Solids
AvKaden Richard Alan Hazzard
Häftad, Engelska, 2013
1 122 kr
Skickas inom 10-15 vardagar
The primary focus of this thesis is to theoretically describe nanokelvin experiments in cold atomic gases, which offer the potential to revolutionize our understanding of strongly correlated many-body systems. The thesis attacks major challenges of the field: it proposes and analyzes experimental protocols to create new and interesting states of matter and introduces theoretical techniques to describe probes of these states. The phenomena considered include the fractional quantum Hall effect, spectroscopy of strongly correlated states, and quantum criticality, among others. The thesis also clarifies experiments on disordered quantum solids, which display a variety of exotic phenomena and are candidates to exhibit so-called "supersolidity." It collects experimental results and constrains their interpretation through theoretical considerations.This Doctoral Thesis has been accepted by Cornell University, Ithaca, USA.
Investigating the Nucleation, Growth, and Energy Levels of Organic Semiconductors for High Performance Plastic Electronics
AvAjay Virkar
Häftad, Engelska, 2013
564 kr
Skickas inom 10-15 vardagar
This thesis details the significant progress made in improving the performance of organic transistors and the network conductivity of carbon nanotubes. The first section investigates organic semiconductor nucleation and growth on the most common dielectric surface used to fabricate organic thin film transistors. The nucleation and growth of the semiconductor was determined to be a critical factor affecting the device performance. Excellent dielectric modification layers, which promote desirable semiconductor growth leading to high conductivity were identified, and a technologically relevant deposition technique was developed to fabricate high quality dielectric modification layers over large areas. This may represent an important step towards the realization of large area organic circuity. In the final section, lessons learned from studying organic semiconductor nucleation and growth were utilized to improve the conductivity of carbon nanotube networks. Selective nucleation of materials at the junctions between nanotubes in the network significantly decreased the network's sheet resistance. The resulting networks may be promising candidates for transparent electrodes with a variety of optoelectronic applications.
On the Formation of the Most Massive Stars in the Galaxy
AvRoberto J. Galván-Madrid
Häftad, Engelska, 2012
564 kr
Skickas inom 10-15 vardagar
The most massive stars in the galaxy - those with more than 15 to 20 solar masses - are lilkely to ionize their surroundings before they reach their final mass. How can they accrete in spite of the presence of over-pressurized gas? This thesis presents results of Submillimeter Array (SMA) and Very Large Array (VLA) studies of massive star formation regions in the early stages of ionization, as well as an analysis of numerical simulations of the evolution of these young HII regions. The results favor a picture in which very massive stars form in accretion flows that are partially ionized and that keep accreting material from their environment.
Factors Affecting the Removal of Ammonia from Air on Carbonaceous Materials
Investigation of Reactive Adsorption Mechanism
AvCamille Petit
Inbunden, Engelska, 2012
1 122 kr
Skickas inom 10-15 vardagar
Air pollution related to the release of industrial toxic gases, represents one of the main concerns of our modern world owing to its detrimental effect on the environment. To tackle this growing issue, efficient ways to reduce/control the release of pollutants are required. Adsorption of gases on porous materials appears as a potential solution. However, the physisorption of small molecules of gases such as ammonia is limited at ambient conditions. For their removal, adsorbents providing strong adsorption forces must be used/developed. In this study, new carbon-based materials are prepared and tested for ammonia adsorption at ambient conditions. Characterization of the adsorbents’ texture and surface chemistry is performed before and after exposure to ammonia to identify the features responsible for high adsorption capacity and for controlling the mechanisms of retention. The characterization techniques include: nitrogen adsorption, thermal analysis, potentiometric titration, FT-IR spectroscopy, X-ray diffraction, Energy Dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Electron Microscopy. The results obtained indicate that ammonia removal is governed by the adsorbent’s surface chemistry. On the contrary, porosity (and thus physisorption) plays a secondary role in this process, unless strong dispersive forces are provided by the adsorbent. The surface chemistry features responsible for the enhanced ammonia adsorption include the presence of oxygen-(carboxyl, hydroxyl, epoxy) and sulfur- (sulfonic) containing groups. Metallic species improve the breakthrough capacity as well as they lead to the formation of Lewis acid-base interactions, hydrogen-bonding or complexation. In addition to the latter three mechanisms, ammonia is retained on the adsorbent surface via Brønsted acid-base interactions or via specific reactions with the adsorbent’s functionalities leading to the incorporation of ammonia intothe adsorbent’s matrix. Another mechanism involves dissolution of ammonia in water when moisture is present in the system. Even though this process increases the breakthrough capacity of a material, it provides rather weak retention forces since ammonia dissolved in water is easily desorbed from the adsorbent’s surface.
Power Scaling of Enhancement Cavities for Nonlinear Optics
AvIoachim Pupeza
Inbunden, Engelska, 2012
564 kr
Skickas inom 10-15 vardagar
Enhancement cavities are passive optical resonators in which continuous-wave laser radiation or pulses of a frequency comb are coherently overlapped, allowing for a power and intensity scaling of up to several orders of magnitude. A prominent application is the table-top generation of bright, laser-like radiation in spectral regions where direct laser action is inefficient or not available at all, via intracavity nonlinear optical processes. However, to exploit the full capacity of this technique further progress is needed. This thesis covers central problems of enhancement cavities, such as finding limitations in scaling the circulating power, measuring cavity parameters with high accuracy, tailoring transverse modes and coupling out radiation generated in the cavity. Unprecedented intracavity laser powers were demonstrated, surpassing previous results by an order of magnitude. As an application, harmonics of the fundamental 1040-nm radiation up to the 21st order are generated. Besides reporting these fine experimental results, the thesis provides an excellent introduction into the physics of enhancement cavities, supported by more than 140 references.
Privacy-Preserving Machine Learning for Speech Processing
AvManas A. Pathak
Inbunden, Engelska, 2012
1 122 kr
Skickas inom 10-15 vardagar
This thesis discusses the privacy issues in speech-based applications such as biometric authentication, surveillance, and external speech processing services. Author Manas A. Pathak presents solutions for privacy-preserving speech processing applications such as speaker verification, speaker identification and speech recognition. The author also introduces some of the tools from cryptography and machine learning and current techniques for improving the efficiency and scalability of the presented solutions. Experiments with prototype implementations of the solutions for execution time and accuracy on standardized speech datasets are also included in the text. Using the framework proposed may now make it possible for a surveillance agency to listen for a known terrorist without being able to hear conversation from non-targeted, innocent civilians.
Three Dimensional Solar Cells Based on Optical Confinement Geometries
AvYuan Li
Inbunden, Engelska, 2012
1 122 kr
Skickas inom 10-15 vardagar
Three dimensional (3D) optical geometries are becoming more common in the literature and lexicon of solar cells. Three Dimensional Solar Cells Based on Optical Confinement Geometries describes and reveals the basic operational nuances of 3D photovoltaics using three standard tools: Equivalent Circuit Models, Ray Tracing Optics in the Cavity, and Absorber Spectral Response. These tools aide in understanding experimental absorption profile and device parameters including Jsc, Voc, Fill Factor, and EQE. These methods also apply to individual optical confinement geometry device, integrated optical confinement geometry device, and hybrid optical confinement geometry device. Additionally, this book discusses the importance of these methods in achieving the goal of high efficiency solar cells and suggests a possible application in large-scale photovoltaics business, like solar farms.
Fundamental Tests of Physics with Optically Trapped Microspheres
AvTongcang Li
Inbunden, Engelska, 2012
1 122 kr
Skickas inom 10-15 vardagar
Fundamental Tests of Physics with Optically Trapped Microspheres details experiments on studying the Brownian motion of an optically trapped microsphere with ultrahigh resolution and the cooling of its motion towards the quantum ground state. Glass microspheres were trapped in water, air, and vacuum with optical tweezers; and a detection system that can monitor the position of a trapped microsphere with Angstrom spatial resolution and microsecond temporal resolution was developed to study the Brownian motion of a trapped microsphere in air over a wide range of pressures. The instantaneous velocity of a Brownian particle, in particular, was studied for the very first time, and the results provide direct verification of the Maxwell-Boltzmann velocity distribution and the energy equipartition theorem for a Brownian particle. For short time scales, the ballistic regime of Brownian motion is observed, in contrast to the usual diffusive regime. In vacuum, active feedback is used to cool the center-of-mass motion of an optically trapped microsphere from room temperature to a minimum temperature of about 1.5 mK. This is an important step toward studying the quantum behaviors of a macroscopic particle trapped in vacuum.
Resource Allocation in Decentralized Systems with Strategic Agents
An Implementation Theory Approach
AvAli Kakhbod
Inbunden, Engelska, 2013
1 032 kr
Skickas inom 10-15 vardagar
This thesis presents a significant contribution to decentralized resource allocation problems with strategic agents. The study focused on three classes of problems arising in communication networks. (C1). Unicast service provisioning in wired networks. (C2). Multi-rate multicast service provisioning in wired networks. (C3). Power allocation and spectrum sharing in multi-user multi-channel wireless communication systems. Problems in (C1) are market problems; problems in (C2) are a combination of markets and public goods; problems in (C3) are public goods. Dr. Kakhbod developed game forms/mechanisms for unicast and multi-rate multicast service provisioning that possess specific properties. First, the allocations corresponding to all Nash equilibria (NE) of the games induced by the mechanisms are optimal solutions of the corresponding centralized allocation problems, where the objective is the maximization of the sum of the agents' utilities. Second, the strategic agents voluntarily participate in the allocation process. Third, the budget is balanced at the allocations corresponding to all NE of the game induced by the mechanism as well as at all other feasible allocations. For the power allocation and spectrum sharing problem, he developed a game form that possesses the second and third properties as detailed above along with a fourth property: the allocations corresponding to all NE of the game induced by the mechanism are Pareto optimal. The thesis contributes to the state of the art of mechanism design theory. In particular, designing efficient mechanisms for the class of problems that are a combination of markets and public goods, for the first time, have been addressed in this thesis. The exposition, although highly rigorous and technical, is elegant and insightful which makes this thesis work easily accessible to those just entering this field and will also be much appreciated by experts in the field.

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Muonium-antimuonium Oscillations in an Extended Minimal Supersymmetric Standard Model

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Search for Muon Neutrino to Electron Neutrino Oscillations in the MINOS Experiment

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