Dissertations / Theses: 'Physics generator'

1

Potter, Rudolf H. "Marx Generator Charged via Biperiodic Resonant Cascaded Transformers." Thesis, Indiana University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10682041.

Full text

Abstract:

In this work, a novel method for charging solid state Marx generators is described for the first time. We first review the utility of modulators for powering high power microwave devices. The principal of operation of the Marx generator is then described starting with the classic topology and leading to solid state topologies. The concept of a generalized Marx generator is introduced and several methods of charging are discussed. A resonant cascaded transformers topology emerges from this discussion. Resonant modes are discussed and the topology is refined to take advantage of the pi/2 mode leading to the circuit that is the focus of this work. We begin our analysis of this circuit by considering the corresponding infinite biperiodic system and derive the characteristic dispersion relation. Motivation for closing the stopband is discussed and benefits of the pi/2 mode are noted. We proceed next to derive the matrix equation for the corresponding lossless system of coupled oscillators. To test and verify the analytic work, a five cell benchtop prototype of the charging system is built and its resonant modes are determined empirically. Capacitors in odd numbered resonators are each connected to the input of a voltage doubler circuit and high voltage dc is generated. A MOSFET is added to the output of each doubler circuit and pulsed output is demonstrated. A SPICE simulation of the physical circuit is created. The mode frequencies from the simulation are in good agreement with those measured and calculated. A practical high-power design is considered for the E2V/Teledyne MG7095 magnetron and simulated in SPICE.

APA, Harvard, Vancouver, ISO, and other styles

2

Roussel, Harold. "Solutions of two matrix models for the DIII generator ensemble." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56957.

Full text

Abstract:

In this work we solve two new matrix models, using standard and new techniques. The two models are based on matrix ensembles not previously considered. They are represented by special forms of antisymmetric matrices and are classified in the DIII generator ensemble. It is shown that, in the double scaling limit, their free energy has the same behavior as previous models describing oriented and unoriented surfaces. We also found an additional solution for the chapter 3 model.

APA, Harvard, Vancouver, ISO, and other styles

3

Segergren, Erik. "Direct Drive Generator for Renewable Power Conversion from Water Currents." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6010.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Schwardt, Eckhard Detlef. "Development of a novel high-voltage arbitrary-waveform generator." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/19863.

Full text

Abstract:

Thesis (MSc)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: The dielectric-barrier discharge (DBD) is a source of non-equilibrium plasma that has seen widespread industrial application in recent years. A high-voltage arbitrary-waveform generator has been designed, built and characterised for the purpose of investigating the influence that the applied voltage waveform has on the operation of a DBD. The developed arbitrary-waveform generator is based on the principle of Fourier synthesis. Up to twenty Fourier components are generated by means of a digital circuit board, and then separately amplified by Class-AB amplifiers. Twenty step-up transformers are subsequently used to transform the Fourier components to higher voltages; the summation of the Fourier components are realised by the series connection of the transformer secondary sides. It was found that the digital generation of the Fourier components is very accurate and provides for the easy configuration of arbitrary waveforms. Furthermore, the amplification of the Fourier components by the Class-AB amplifiers introduces very little distortion. The principle of adding the Fourier components via the step-up transformers has been demonstrated; however, the large distributed capacitances of the transformers adversely affect the operation of the Class-AB amplifiers, leading to the introduction of distortion into the generated waveform. Furthermore, it was found that care had to be taken to limit the introduction of EMI through the system’s large ground plane.
AFRIKAANSE OPSOMMING: Die di¨elektriese versperringsontlading (DVO) is ’n bron van nie-ekwilibrium plasma wat in die afgelope jare wye toepassing in die nywerheid gevind het. ’n Arbitrˆere-golfvorm hoogspanningskragbron is ontwerp, gebou en gekarakteriseer, met die doel om die invloed wat die aangewende spanningsgolfvorm het op die werking van die DVO, te ondersoek. Die ontwikkelde arbitrˆere golfvormgenerator is gebaseer op die beginsels van Fourier samestelling. Tot twintig Fourier komponente word digitaal gegenereer, en dan afsonderlik versterk deur Klas-AB versterkers. Twintig transformators word dan gebruik om die Fourier komponente na ho¨er spannings te transformeer. Die sommasie van die Fourier komponente geskied deur die serieskakeling van die transformators se sekondˆere windings. Daar is bevind dat die digitale generasie van die Fourier komponente baie akkuraat is, en dat die arbitrˆere golfvorms maklik verstel kan word. Verder versterk die Klas-AB versterkers die Fourier komponente sonder enige noemenswaardige vervorming. Die gebruik van die transformators om die Fourier komponente saam te voeg, is gedemonstreer. Die groot verspreide kapasitansies van die transformators be¨ınvloed egter die funksioneering van die Klas-AB versterkers, wat lei tot ’n vervorming van die uittree. Daar is ook bevind dat die toetrede van EM versteurings deur die grondvlak van die sisteem problematies kan wees.

APA, Harvard, Vancouver, ISO, and other styles

5

Liu, Hongqin 1956. "Simulation of a plasma particle generator." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31571.

Full text

Abstract:

The goal of this research was to simulate the nucleation and particle growth in a tubular plasma particle generator and investigate the effects of various entrance and boundary conditions on the particle size distribution and production rate.
The fluid flow is laminar and its domain is two-dimensional axi-symmetric and a radial quench gas injection is introduced. The method of moments was used to model the particle generation and growth starting with the dynamic aerosol equation and the assumption of a log-normal distribution function. The governing equations are solved numerically and the velocity, concentration, temperature, particle size and density profiles are obtained for various entrance and boundary conditions.
The following conclusions were reached: increasing the length of the generator tube or metal concentration gives more product, larger particle size and narrower size distribution; higher quench gas injection rates or entrance flow rate produces finer particles with a broader size distribution; increasing entrance temperature leads to smaller particles with narrower size distribution.
In addition, for a quick prediction, an artificial neural network (ANN) model was used. The ANN was trained with the data from the numerical simulations. Within the ranges of conditions examined, the output can be obtained in few seconds rather than several hours needed in the original simulations.

APA, Harvard, Vancouver, ISO, and other styles

6

McKee, Erik Scott. "Neutron Production from Z-pinch Plasmas at the 1 MA Zebra Generator." Thesis, University of Nevada, Reno, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10247687.

Full text

Abstract:

Neutrons produced deuterium Z-pinch plasmas are widely acknowledged to be a consequence of highly accelerated deuterons undergoing nuclear fusion with relatively stationary deuterons. The acceleration is thought to occur in intense fields created in the MHD instabilities that punctuate the plasma column. Interestingly, the energies of the accelerated ions exceed the applied voltage across the electrode gap. We use the 1 MA Zebra pulsed-power generator at the Nevada Terawatt Facility (NTF) to explore this poorly understood fast neutron production mechanism by creating deuterium Z-pinches in three distinct types of target loads. The loads are a cylindrical shell of deuterium gas, the far less explored deuterided palladium wire arrays, and a deuterium-carbon ablated laser plume target, which is unique to the NTF.

The pinch dynamics vary considerably in these three targets and provide the opportunity to explore the ion acceleration mechanism. We infer the characteristics of the accelerating fields from a wide range of diagnostic data including the neutron yield, energy spectrum and angular distribution, and the properties of the matching electron beams that are accelerated in the same field, and the energetic X-rays they produce on stopping. The plasma and the instabilities were recorded on several high-speed imaging diagnostics along with time-integrated soft (<10 keV) X-ray pinhole images. The three load types produced total neutron yields in the 10⁸–10¹⁰ n/pulse range. The synchronization we observe between the ion and electron beams and the development of instabilities leads us to conrm the acceleration hypothesis. We also present the characteristics of the fields and ion beams in these varied pinches.

APA, Harvard, Vancouver, ISO, and other styles

7

Lachance, Bernard 1967. "A new penumbra generator for matching of electron for matching of electron fields." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24018.

Full text

Abstract:

We describe the geometric and dosimetric characteristics of a device developed to modify the penumbra of an electron beam and thereby improve the dose uniformity in the overlap region when fields are abutted. The device is a Lipowitz metal block placed on top of the electron applicator's insertion plate and positioned to stop part of the electron beam. The air-scattered electrons beyond the block increase the penumbra width from about 1.4 to 2.7-3.4 cm. The modified penumbra is broad and almost linear at all depths for the 9 MeV and 12 MeV electron beams used in this study. Film dosimetry was used to obtain beam profiles and isodose distributions. Without the penumbra generator, lateral setup errors of 2 to 3 mm may introduce dose variations of up to 20% in the junction region. Similar setup errors cause less than 5% dose variations when the penumbra generator is used to match the fields.

APA, Harvard, Vancouver, ISO, and other styles

8

Bolund, Björn. "Electric Power Generation and Storage Using a High Voltage Approach." Doctoral thesis, Uppsala University, Department of Engineering Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6833.

Full text

Abstract:

Production and consumption of electricity have grown enormously during the last century. No mater what the primary source of energy is, almost all generation of electricity comes from conversion of a rotational movement in a generator. The aim of this thesis is to see how high voltage technology influence production and storage of electricity. Power flow in the generators used to convert mechanical movement to electric energy is analyzed using Poynting‘s vector. The impact of new generator technology for efficient extraction of hydroelectric power is shown. Simulation of a large permanent magnet turbo generator is presented. A flywheel storage system for electric vehicles utilizing high voltage technology is also presented. In pulsed power applications, a cheap method for intermediate storage of energy during milliseconds, which enables an inductive primary storage is presented and experimentally tested.

APA, Harvard, Vancouver, ISO, and other styles

9

Danielsson, Oskar. "Wave Energy Conversion : Linear Synchronous Permanent Magnet Generator." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7194.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Andriatis, Alexander. "Generator-level acceptance for the measurement of the inclusive cross section of W-boson and Z-boson production in pp collisions at [square root of] s = 5 TeV with the CMS detector at the LHC." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115668.

Full text

Abstract:

Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 39-42).
The inclusive cross section of vector boson production in proton-proton collisions is one of the key measurements for constraining the Standard Model and an important part of the physics program at the LHC. Measurement of the inclusive cross section requires calculating the detector acceptance of decay products. The acceptance of the CMS detector of leptonic decays of W and Z bosons produced in pp colisions at [square root of]s = 5 TeV is calculated using Monte Carlo event simulation. Statistical and systematic uncertainties on the acceptance measurement from PDF and a, uncertainty and higher-order correction are reported. The use of the calculated acceptance in combination with measurements of detector efficiency, luminosity, and particle counting to determine the inclusive cross section is outlined. A total integrated luminosity of 331.64 pb-1 from 2015 and 2017 CMS data at [square root of]s = 5 TeV is available for the calculation of the inclusive cross section.
by Alexander Andriatis
S.B.

APA, Harvard, Vancouver, ISO, and other styles

11

Edler, Daniel. "Interactive map generator for simplifying and highlighting important structures in large networks." Thesis, Umeå University, Department of Physics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-34816.

Full text

Abstract:

Understanding the structure of a network is an essential part in understanding the behavior of the system it represents, but as the system becomes really large, a visualization of the full network looses its potential to reveal important structural relationships. Then we need ways to simplify and highlight the important structures of the network while the details are filtered out, just like good maps do. We have developed an interactive application that utilizes mathematical methods based on network and information theory to reveal the important patterns hidden in huge amount of interaction data. The application gives the professional as well as the nonprofessional user the ability to load his or hers own file containing the network data, from mobile phone networks and social online networks to transport networks and financial networks and lets you explore the data and generate a customized map which highlights the influential patterns in your data. A demo application is also developed to demonstrate the mathematical and information-theoretical principles behind the map generation.

För att koppla form till funktion är nätverk ett oumbärligt verktyg, men när systemen blir riktigt stora förlorar nätverken sin förmåga att avslöja viktiga strukturella samband. Då behövs det kraftfulla metoder för att förenkla och framhäva de viktiga strukturerna i nätverken samtidigt som detaljerna filtreras bort, precis som bra kartor gör. Vi har utvecklat en interaktiv applikation som utnyttjar matematiska metoder baserat på nätverks- och in- formationsteori för att avslöja viktiga mönster som ligger dolt i myllret av interaktionsdata. Du kan läsa in din egen fil med nätverksdata, från telekommunikationsnätverk och sociala online-nätverk till transportnärverk och finansiella nätverk, och få tillbaka en skräddarsydd karta som låter dig upptäcka de inflytelserika mönstren i nätverket. En demo-applikation är också utvecklad för att demonstrera de matematiska och informationsteoretiska principerna bakom kartgenereringen.

APA, Harvard, Vancouver, ISO, and other styles

12

Chalasani, Dheeraj. "FEASIBILITY OF A PLASMA CONTACT FOR FARADAY GENERATORS." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367560698.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Eriksson, Mikael. "Modelling and Experimental Verification of Direct Drive Wave Energy Conversion : Buoy-Generator Dynamics." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7785.

Full text

Abstract:

This thesis is focused on development of models and modelling of a wave energy converter in operation. Through the thesis linear potential wave theory has been used to describe the wave-buoy interaction. The differences lie in the generator models, in the simplest model the generator is a mechanical damper characterized by a damping factor. In the most advanced generator model the magnetic fields is calculated the by a FE-method, which gives detailed description of the electric properties and the effect it has on the buoy dynamics. Moreover, an equivalent circuit description of the generator has been tested. It has the same accuracy as the field based model but with a strongly enhanced CPU time. All models are verified against full scale experiments. The models are intended to be used for design of the next generation wave energy converters. Further, the developed models have also been used to study what effect buoy geometry and generator damping have on the ability to energy absorption. In the spring 2006 a full scale wave energy converter was installed at the west coast of Sweden. It was in operation and collected data during three months. During that period the load resistance was varied in order to study the effect on the energy absorption. These collected data was then used in the verification of the developed models. In the year 2002 a wave energy project started at Uppsala University; this work is a part of that larger project which intendeds to develop a viable wave energy conversion concept.

APA, Harvard, Vancouver, ISO, and other styles

14

Cavalli, Noemi. "Study of heavy bosons production in 3-3-1 models with the ATLAS detector at LHC." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19300/.

Full text

Abstract:

Tra le teorie oltre il Modello Standard il modello 331 risulta essere una motivata estensione del Modello Standard. Tale modello è di grande interesse fenomenologico e sperimentale poiché costituisce l'unica estensione del Modello Standard che introduce nella teoria sia un bosone doppio carico scalare ($H^{\pm\pm}$) che un bosone doppio carico vettore ($Y^{\pm\pm}$). Lo studio presentato in questo elaborato ha come scopo il determinare una modalità per discriminare il segnale associato al bosone scalare $H^{\pm\pm}$ dal segnale relativo al bosone vettore $Y^{\pm\pm}$, nel caso in cui ad LHC si abbia evidenza sperimentale relativa ad un generico bosone doppio carico, con una trascurabile contaminazione da parte del fondo dal Modello Standard. Si impiegano campioni MC generati per un'energia del centro di massa di $\sqrt{s} = 13$ TeV considerando un benchmark point tale da porre i valori per le masse dei bosoni a $m_{H^{\pm\pm}} = m_{Y^{\pm\pm}} = 1000$ GeV. Il processo preso in esame è $pp \longrightarrow Y^{++}Y^{--}(H^{++}H^{--}) \longrightarrow \ell^+\ell^+\ell'^-\ell'^-$, dove lo stato finale risulta essere comprensivo di due coppie di leptoni aventi uguale sapore e medesima carica elettrica. Tutti i sapori dei leptoni sono considerati. L'analisi, volta a discriminare i due bosoni menzionati, è condotta basandosi sulle distribuzioni ottenute al truth level relative alle variabili associate allo stato finale considerato. Poiché le distribuzioni risultanti non risultano essere sufficientemente differenti da consentire una discriminazione tramite un approccio cut-based, si svolge una analisi multivariata impiegando diversi classificatori: BDTs, MLP e discriminante di Fisher. I tre metodi, allenati e testati, risultano avere prestazioni simili. Sebbene i segnali associati ad $Y^{\pm\pm}$ e $H^{\pm\pm}$ risultino simili, è possibile discriminare il bosone vettore dallo scalare. In particolare, si ottiene un massimo potere di rigetto dell'ipotesi spin 0 al $80\%$ CL.

APA, Harvard, Vancouver, ISO, and other styles

15

Thorburn, Karin. "Electric Energy Conversion Systems : Wave Energy and Hydropower." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7081.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Tiihonen, Mikael. "Spectral Management in Quasi-Phase-Matched Parametric Devices." Doctoral thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4021.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Eriksson, Sandra. "Direct Driven Generators for Vertical Axis Wind Turbines." Doctoral thesis, Uppsala : Acta Universitatis Uppsaliensis, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9210.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Thomas, Karin. "Low Speed Energy Conversion from Marine Currents." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8400.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Siebenmorgen, Christopher B. "Potential climate change impacts on hydrologic regimes in northeast Kansas." Thesis, Kansas State University, 2010. http://hdl.handle.net/2097/6993.

Full text

Abstract:

Master of Science
Department of Biological & Agricultural Engineering
Kyle R. Douglas-Mankin
The Great Plains once encompassed 160 million hectares of grassland in the central United States. In the last several decades, conversion of grassland to urban and agricultural production areas has caused significant increases in runoff and erosion. Past attempts to slow this hydrologic system degradation have shown success, but climate change could once again significantly alter the hydrology. The Intergovernmental Panel on Climate Change (IPCC) studies the state of knowledge pertaining to climate change. The IPCC has developed four possible future scenarios (A1, A2, B1 and B2). The output temperature and precipitation data for Northeast Kansas from fifteen A2 General Circulation Models (GCMs) were analyzed in this study. This analysis showed that future temperature increases are consistent among the GCMs. On the other hand, precipitation projections varied greatly among GCMs both on annual and monthly scales. It is clear that the results of a hydrologic study will vary depending on which GCM is used to generate future climate data. To overcome this difficulty, a way to take all GCMs into account in a hydrologic analysis is needed. Separate methods were used to develop three groups of scenarios from the output of fifteen A2 GCMs. Using a stochastic weather generator, WINDS, monthly adjustments for future temperature and precipitation were applied to actual statistics from the 1961 – 1990 to generate 105 years of data for each climate scenario. The SWAT model was used to simulate watershed processes for each scenario. The streamflow output was analyzed with the Indicators of Hydrologic Alteration program, which calculated multiple hydrologic indices that were then compared back to a baseline scenario. This analysis showed that large changes in projected annual precipitation caused significant hydrologic alteration. Similar alterations were obtained using scenarios with minimal annual precipitation change. This was accomplished with seasonal shifts in precipitation, or by significantly increasing annual temperature. One scenario showing an increase in spring precipitation accompanied by a decrease in summer precipitation caused an increase in both flood and drought events for the study area. The results of this study show that climate change has the potential to alter hydrologic regimes in Northeast Kansas.

APA, Harvard, Vancouver, ISO, and other styles

20

Skolimoski, Kellen Nunes. "Cosmologia na teoria e na prática: possibilidades e limitações no ensino." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/81/81131/tde-09042015-154106/.

Full text

Abstract:

Com esta pesquisa estudamos quais são as possibilidades e as dificuldades de trabalhar a cosmologia nas aulas de física do ensino médio, uma vez que é um assunto com uma profunda riqueza sobre a história e a filosofia da ciência (HFC) e que pode facilita o entendimento da natureza do conhecimento científico (NdC), o que nos possibilita ensinar ciências de uma forma mais condizente com sua origem e seu desenvolvimento. Por isso, apresentamos neste trabalho, uma série de modelos sobre a origem do universo, partindo desde os mitos de criação de civilizações antigas, passando por alguns dos principais modelos filosóficos e clássicos até chegar aos modelos cosmológicos modernos. Para facilitar a comparação entre esses modelos sintetizamos suas características por meio do mapeamento conceitual. Porém, não é objetivo deste trabalho fazer um estudo histórico do desenvolvimento da cosmologia, mas apresentar alguns modelos que trazem elementos pertinentes de serem levados para uma aula de física. Acreditamos que a cosmologia possa motivar os alunos a se interessarem mais pelo conhecimento científico, já que ela naturalmente desperta a imaginação e a curiosidade dos seres humanos desde a antiguidade. Também entendemos que a cosmologia pode facilitar a inserção da física moderna e contemporânea nas aulas do ensino médio, além de também possibilitar uma relação direta com diversos temas da física clássica, uma vez que alguns desses conteúdos foram desenvolvidos numa tentativa de explicar a evolução do universo. Apesar de acreditarmos na importância de usar a cosmologia para melhorar o conteúdo físico oferecido no ensino médio das escolas do estado de São Paulo, sabemos também que são grandes as dificuldades para sua aplicação, por isso, debruçamos nossa atenção sobre esses problemas numa tentativa de mapeá-los. Com esses objetivos realizamos uma pesquisa empírica de natureza diagnóstica, visando investigar as possibilidades e as dificuldades em trabalhar esse tema no ensino médio, sob o ponto de vista de professores de física que conhecem bem a realidade escolar, das instituições de ensino público estadual. Os resultados apontam uma série de possibilidades na exploração do tema, como: o interesse que a maioria dos alunos tem pelo assunto; o rico contexto histórico e filosófico; a facilidade que o tema oferece para um trabalho interdisciplinar, entre outras. Além disso, os resultados também apontam problemas relacionados à falta de formação adequada; a falta de motivação dos professores em inovar suas aulas, devido a condições desgastantes impostas pela estrutura profissional; a saturação de conteúdos no currículo de física para pouca quantidade de aulas semanais e um possível embate religioso na apresentação de modelos como o Big Bang, uma vez que boa parte dos alunos tem origem cristã. Tais possibilidades e dificuldades foram apresentadas na forma de mapas conceituais, com o objetivo final de fornecer subsídios para futuros estudos sobre a inserção da cosmologia no ensino médio.
With this research we studied what are the possibilities and difficulties of working the cosmology in physics classes in secondary education, since it is a very rich subject about the history and philosophy of science (HFC) and facilitates understanding the nature of the scientific knowledge (NdC), which enables us to teach science in a more consistent way with its origin and development. Therefore, we present in this work, a series of models about the origins of the universe, from the creation myths of ancient civilizations, passing by some of the main philosophical and classical models to reach the modern cosmological models. However, it is not the aim of this work to make a historical study of the development of cosmology, but present some models that bring relevant elements being taken into account for a physics class. We believe that cosmology can motivate students to become more interested in scientific knowledge, since it naturally arouses the imagination and curiosity of humans since antiquity. We also understand that cosmology can facilitate the insertion of modern and contemporary physics in secondary education classes, and also enable a direct relationship with various themes of classical physics, since some content have been developed in an attempt of explaining the evolution of the universe. Although we believe in the importance of using cosmology to improve the physical content offered in secondary education schools in the state of São Paulo, we also know that there are great difficulties in its application, so we focus our attention on these issues in an attempt to map them. With these objectives we conducted an empirical study of diagnostic nature, aiming to investigate the possibilities and difficulties in working this issue in the secondary education, from the point of view of physics teachers who know the school reality of the State public education institutions. The results suggest a number of possibilities in exploration of the theme, such as: the interest which the majority of students have ion such subject, the rich historical and philosophical context, how easy the theme is in order to offer an interdisciplinary work, among others. Moreover, the results also point to problems related to lack of adequate education; the lack of motivation of the teachers to innovate their classes due to stressful conditions imposed by the professional structure; saturation of content in the curriculum of physics having just a few weekly classes to teach it and a possible religious confrontation in presenting models like the Big Bang, once a great part of the students have a Christian origin. With the results found we made a mapping of such possibilities and difficulties, which were presented in the form of conceptual maps, with the ultimate goal of providing insights for future studies on the insertion of cosmology in the secondary education.

APA, Harvard, Vancouver, ISO, and other styles

21

Colmenares, Julian, and Diyar Ghazi. "Plasma Burner: Numerical Modeling of Plasma Generation and Flow." Thesis, Luleå tekniska universitet, Rymdteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-87161.

Full text

Abstract:

Technological evolution and mass production is impacting the Earth daily due to global warming caused by greenhouse gas emissions, where the biggest factor is the emission of carbon dioxide mostly caused by the burning of fossil fuel and industrial processes. Therefore, alternatives for substituting the use of fossil fuel in industries are extremely important. This thesis project investigates the method of using plasma technology using a plasma burner which is electrically generated and could be an ideal solution for industrial metallurgical, chemical and mechanical processes due to its unique characteristics such as high energy densities, extremely high temperatures, rapid heating of surfaces and melting materials with a small installation size. Using the software COMSOL Multiphysics, a 2D model geometry is set up to simulate and investigate the behavior of the plasma burner by varying different parameters to improve the performance of the plasma burner. The results are based on simulations and no experiments were performed. However, we visited RISE ETC to observe and learn about the plasma burner model. At last, a geometry investigation was done by calculating the thermal efficiency to designate the most efficient geometry.

APA, Harvard, Vancouver, ISO, and other styles

22

Waters, Rafael. "Energy from Ocean Waves : Full Scale Experimental Verification of a Wave Energy Converter." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9404.

Full text

Abstract:

A wave energy converter has been constructed and its function and operational characteristics have been thoroughly investigated and published. The wave energy converter was installed in March of 2006 approximately two kilometers off the Swedish west coast in the proximity of the town Lysekil. Since then the converter has been submerged at the research site for over two and a half years and in operation during three time periods for a total of 12 months, the latest being during five months of 2008. Throughout this time the generated electricity has been transmitted to shore and operational data has been recorded. The wave energy converter and its connected electrical system has been continually upgraded and each of the three operational periods have investigated more advanced stages in the progression toward grid connection. The wave energy system has faced the challenges of the ocean and initial results and insights have been reached, most important being that the overall wave energy concept has been verified. Experiments have shown that slowly varying power generation from ocean waves is possible. Apart from the wave energy converter, three shorter studies have been performed. A sensor was designed for measuring the air gap width of the linear generator used in the wave energy converter. The sensor consists of an etched coil, a search coil, that functions passively through induction. Theory and experiment showed good agreement. The Swedish west coast wave climate has been studied in detail. The study used eight years of wave data from 13 sites in the Skagerrak and Kattegatt, and data from a wave measurement buoy located at the wave energy research site. The study resulted in scatter diagrams, hundred year extreme wave estimations, and a mapping of the energy flux in the area. The average energy flux was found to be approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the near shore Skagerrak, and 2.4 kW/m in the Kattegat. A method for evaluating renewable energy technologies in terms of economy and engineering solutions has been investigated. The match between the technologies and the fundamental physics of renewable energy sources can be given in terms of the technology’s utilization. It is argued that engineers should strive for a high utilization if competitive technologies are to be developed.

APA, Harvard, Vancouver, ISO, and other styles

23

Edhammer, Jens. "Rigid Body Physics for Synthetic Data Generation." Thesis, Linköpings universitet, Informationskodning, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129808.

Full text

Abstract:

For synthetic data generation with concave collision objects, two physics simu- lations techniques are investigated; convex decomposition of mesh models for globally concave collision results, used with the physics simulation library Bullet, and a GPU implemented rigid body solver using spherical decomposition and impulse based physics with a spatial sorting-based collision detection. Using the GPU solution for rigid body physics suggested in the thesis scenes con- taining large amounts of bodies results in a rigid body simulation up to 2 times faster than Bullet 2.83.

APA, Harvard, Vancouver, ISO, and other styles

24

Barnett, William Halbert. "Duty Cycle Maintenance in an Artificial Neuron." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/phy_astr_theses/7.

Full text

Abstract:

Neuroprosthetics is at the intersection of neuroscience, biomedical engineering, and physics. A biocompatible neuroprosthesis contains artificial neurons exhibiting biophysically plausible dynamics. Hybrid systems analysis could be used to prototype such artificial neurons. Biohybrid systems are composed of artificial and living neurons coupled via real-time computing and dynamic clamp. Model neurons must be thoroughly tested before coupled with a living cell. We use bifurcation theory to identify hazardous regimes of activity that may compromise biocompatibility and to identify control strategies for regimes of activity desirable for functional behavior. We construct real-time artificial neurons for the analysis of hybrid systems and demonstrate a mechanism through which an artificial neuron could maintain duty cycle independent of variations in period.

APA, Harvard, Vancouver, ISO, and other styles

25

Campbell, Lawrence Thomas. "The physics of a 4th generation light source." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18915.

Full text

Abstract:

This thesis describes an unaveraged 3D mathematical model and parallel code of the free electron laser. It is unique in that it is a 3D model which does not perform limiting assumptions performed by commonly used FEL codes. ) This allows it to model the FEL with a higher resolution, and to model effects which other codes cannot. The code is written in Fortran 90. The enhanced frequency range results in an increased memory and process uptake, and so the code is written for use on parallel processors using the MPI standard. The problems associated with finding an efficient method of parallelization of the FEL system are described and solutions are considered. The enhanced frequency range also results in a model of diffraction in the transverse dimensions which is frequency dependant, which becomes problematic at low frequencies. To solve this, a low frequency cut-off is defined, and the frequencies below the cut-off are filtered out during the simulations. Several simulations are presented to test the code against previously published results with the enhanced frequency range in ID; Then 3D simulations are pre- sented showing the amplification arising from effects which cannot be predicted in more commonly used codes. Finally, a new effect is reported involving the evolution of short chirped electron bunches in an undulator.

APA, Harvard, Vancouver, ISO, and other styles

26

Bullock, Ben Kasmin. "Third generation fermions as probes of new physics." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5487/.

Full text

Abstract:

This thesis concerns the properties of two particles, the top quark and the tau lepton, the heaviest of the quarks and leptons, respectively, in the standard model of elementary particle physics. After a chapter introducing the standard model, the second concerns the tau lepton. Amongst all the quarks and leptons, the tau has the unique property that its polarisation can readily be measured at high energy colliders. We propose and develop new methods of using this unique property to search for new physics, such as Higgs bosons, and also for making an accurate measurement of the polarisation of taus produced via Z decay leading to a precision determination of the electroweak coupling. The third chapter of this thesis concerns the top quark. We perform the complete one- loop radiative corrections to the helicity amplitudes within the standard model. Even though the radiative corrections to top quark production and decay have already been calculated separately, our work makes it possible to combine the sequence of events by keeping full information on the correlations among final state particles.

APA, Harvard, Vancouver, ISO, and other styles

27

Robinson, Thomas A. "Quasi-phase-matching of high-harmonic generation." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:dd3b4ad3-5e57-40fc-94b0-98bb32596729.

Full text

Abstract:

This thesis describes the use of counterpropagating pulse trains to quasi-phase-match high-harmonic generation (HHG). Two novel techniques for generating trains of ultrafast pulses are described and demonstrated. The first method makes use of a birefringent crystal array to split a single pulse into a sequence of pulses. The second method makes use of the time-varying polarisation of a chirped pulse passed through a multiple-order wave plate to generate a train of pulses by the addition of a polariser. It is demonstrated that this second technique can be used to make pulse trains with non-uniform pulse separation by using an acousto-optic programmable dispersive filter to manipulate the higher-order dispersion encountered by the chirped pulse. The crystal array method is used to demonstrate quasi-phase-matching of HHG in a gas-filled capillary, using one and two counterpropagating pulses. Enhancements of up to 60% of the intensity of the 27th harmonic of the 800,nm driving laser light are observed. Information on the spatial and dynamic properties of the HHG process is obtained from measurements of the coherence length in the capillary. Simulations of HHG in a capillary waveguide have been performed. These agree well with the results of the quasi-phase-matching experiments. The effect of mode-beating on the generation process in a capillary and its use as a quasi-phase-matching mechanism are investigated.

APA, Harvard, Vancouver, ISO, and other styles

28

Tyler, Robert H. "Electromagnetic fields generated by ocean currents and the potential for using geomagnetic data in ocean and climate studies." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39884.

Full text

Abstract:

The ocean currents flowing through the earth's main magnetic field are known to induce secondary magnetic fields. Hence, variations in the ocean circulation induce variations in the net magnetic field. This research is aimed at exploring the potential for using geomagnetic data to study variability in ocean circulation and climate.
First, general relativity theory is used to formally establish the proper set of electromagnetic equations to be used for observers in a rotating (accelerating) frame of reference observing a medium (the ocean, in this case) with relative velocity. Extra terms due to rotation are derived and described and a generalized Schiff's charge density is shown to be potentially significant for the application to ocean circulation.
We extend the theory of electromagnetic fields generated by ocean currents. Many analytical solutions are found for idealized ocean features including sheared flow, jets, and a Stommel gyre. Results indicate that the ocean-induced magnetic fields will typically have magnitudes of 10's-100's of nT within the ocean. Outside of the ocean, the magnitudes are smaller (typically 1-10 nT) but decay on scales set by the horizontal scale of the ocean feature.
We investigate the time-scales associated with the adjustment of electromagnetic fields generated by low-frequency ocean currents. We find that the time scales can be quite long, prohibiting a quasistatic assumption in the treatment of the electromagnetic fields generated by the important tidal, inertial, and diurnal-frequency ocean currents.
Three-dimensional explicit time-dependent and steady-state finite-difference numerical models are constructed to study the electromagnetic fields generated by more realistic ocean current and conductivity features.
The ocean currents generate electromagnetic forces on the fluid at the surface of the earth's core. If these forces lead to significant core motion, the effect of the oceans on the generation and variability of the earth's magnetic field may be nontrivial. We estimate the form and magnitude of these forces and make comparisons with observations. Despite many uncertainties, we find evidence to suggest the ocean forcing mechanism may be significant and conclude that this process should be further investigated in the context of a larger study.
This work indicates that it is likely that the geomagnetic record has captured oceanic signals. From a preliminary data analyses we find that aside from the oceanic tidal signals, the magnetic record shows other signals of possible oceanic origin including an apparent correlation between magnetic records from the equatorial Pacific and the Southern Oscillation Index. We discuss the prerequisites that are necessary to extract information about ocean circulation variability from the geomagnetic record.

APA, Harvard, Vancouver, ISO, and other styles

29

Ikiades, Aristidis Anthony. "Optical generation of microwaves." Thesis, University of Kent, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334037.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Matos, Antonio P. "Characterization and application of four-layer semiconductor structures in pulse mode operation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Sep%5FMatos.pdf.

Full text

Abstract:

Thesis (M.S. in Physics)--Naval Postgraduate School, September 2006.
Thesis Advisor(s): Gamani Karunasiri, James H. Luscombe. "September 2006." Includes bibliographical references (p. 69-70). Also available in print.

APA, Harvard, Vancouver, ISO, and other styles

31

Punch, Sean M. "Radiative mass generation from new Physics in the Quark sector." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56763.

Full text

Abstract:

A model is presented which consists of a dynamical scheme for reproducing the mass hierarchies observed in the quark sector. This is accomplished through new physics beyond the Standard Model, and does not rely upon the Higgs mechanism. By introducing a heavy fermion which couples to the quarks via the emission and reabsorption of a new boson, initially massless quarks are given their masses in a purely radiative fashion. The differences between up and down sector masses appear naturally as a result of generating the down mass matrix from corrections to the up mass matrix: accomplished via an anomalous flavour-changing coupling to the weak sector. Multipole type form-factors are inserted at each coupling, and introduce parameters which are varied to produce numerical fits to the quark masses, mixing angles and CP-violation parameter. Several extensions to the model are proposed and discussed.

APA, Harvard, Vancouver, ISO, and other styles

32

Bengtz, Oskar. "Student-generated representations in Algodoo while solving a physics problem." Thesis, Uppsala universitet, Fysikundervisningens didaktik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355197.

Full text

Abstract:

Fysiklärare möter ofta den svåra uppgiften att representera abstrakta, väldefinierade egenskaper hos den fysiska världen (så som krafter eller energier) för studenter som går bortom ekvationer, grafer eller diagram. I denna studie tittar jag två fall av universitetsstudenter som löser en fysikalisk uppgift, användandes det digitala programmet Algodoo på en stor pekskärm för att undersöka hur studenter naturligt använder sig av sådan teknologi för att återskapa dessa representationer själva. Jag finner att när studenter skapar scener i Algodoo prioriterar de att behålla en viss mått av likhet från den fysiska världen, vilket går bortom den formella behandlingen av uppgifter som studenter kan ha fått lära sig i fysikundervisningen. Vidare, när studenterna använder sig av fysikaliska ekvationer vid lösandet av problemet, verkar de använda Algodoo som ett facit för att se huruvida deras numeriska lösning, uträknad på en klassisk whiteboard, stämmer. På detta sätt - vilket har föreslagits i tidigare forskning - ser jag hur Algodoo, och liknande digitala lärmiljöer, fungerar som en bro mellan studenternas konceptuella förståelse av den fysiska världen, och den mer formella, matematikbaserade beskrivningen vilket används inomfysiken.
Physics teachers are often faced with the difficult task of representing abstract, formally-defined properties of the physical world (such as forces or energy) for students in a way which goes beyond equations, graphs, and diagrams. In this study, I investigate two cases of university students solving a physics problem while using the digital software, Algodoo, on a large touch screen to examine how students might naturally leverage such technology to create such representations of their own. I find that as student draw scenes in Algodoo, they tend to prioritze a degree of resemblance to the physical world which goes beyond the formal treatment of problems they might have been taught in physics classes. Additionally, as the students recruit physics equation into their solution of the problem, they appear to use Algodoo as a conceptual check for the numerical answer they calculate on the normal whiteboard. In this way - and as has been hypothesized in previous research - I see the potential for Algodoo and similar digital learning environments to act as a bridge between students’ conceptual intuitions of the physical world and the more formal, mathematically-based descriptions used in physics.

APA, Harvard, Vancouver, ISO, and other styles

33

Chang, YuChun. "Diffraction wavefront analysis of computer-generated holograms." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284879.

Full text

Abstract:

Computer-generated holograms (CGHs) use diffraction to create wavefronts of light with desired amplitude and phase variations. The amplitude control is well known. But the sensitivity of phase, which is most important for some applications, such as interferometry, is less known. This dissertation studies phase errors resulted from design and fabrication limitations of CGHs. Fabrication uncertainties of CGHs are primarily responsible for the degradation of the quality of wavefronts generated by CGHs. In this dissertation, the binary linear diffraction model is introduced to study wavefront phase errors caused by substrate figure errors, pattern distortion, grating duty-cycle and etching depth errors. Wavefront sensitivity functions derived from diffraction model provide analytical solutions to estimate phase deviations due to duty-cycle or phase depth variations. The results of the wavefront sensitivity analysis also enable us to identify hologram structures that are the most sensitive, as well as the least sensitive to fabrication uncertainties. Experiments were conducted to validate the diffraction model. Example error budgets for common CGH optical testing configurations are demonstrated. In addition, a graphical representation of the diffraction fields is introduced. It provides an intuitive way for diffraction wavefront analysis and explains phase discontinuous observed in the diffraction model. Scalar diffraction models are commonly used in CGH analysis and modeling due to their computational simplicity compared with rigorous diffraction models. The validity of the scalar diffraction models becomes unclear when they are used to analyze diffractive elements with wavelength-scaled features. This dissertation discusses the validity of the scalar diffraction models with giving emphasis to wavefront phase. Fourier modal method (FMM) derived from rigorous diffraction theory is used to study a binary zone plate. The result of this analysis is compared with experimental data, This study shows that polarization sensitivities of the hologram are almost negligible for the chrome-on-glass zone plate with a minimum ring spacing of 2lambda. This result implies that scalar diffraction models may still be sufficient for modeling the phase from holograms with wavelength-scaled diffraction features for the case studied in this dissertation.

APA, Harvard, Vancouver, ISO, and other styles

34

Robbe, P. "Generators, Calorimeter Trigger and J/ψ production at LHCb." Habilitation à diriger des recherches, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00683350.

Full text

Abstract:

Ce document presente des résultats relatifs à la préparation du programme de physique de l'expérience LHCb: développement d'un logiciel de génération, commissioning du trigger calorimètre et mesure de la production des J/psi. Une simulation détaillée est obligatoire pour développer les outils d'analyse nécessaires pour réaliser ce programme et un logiciel de génération détaillé a été implémenté. Celui-ci décrit par exemple le mélange des B et la violation de CP dans les désintégrations des B pour l'environnement hadronique de LHCb. Pour les désintégrations hadroniques, le système de déclenchement de l'expérience est basé sur les calorimètres, en particulier le calorimètre hadronique. La grande section efficace de production au LHC permet de faire, avec les premières données enregistrées par l'expérience, une mesure de la section efficace différentielle des J/psi, et de la comparer avec des modèles thèoriques pour tester QCD dans le secteur des quarks lourds.

APA, Harvard, Vancouver, ISO, and other styles

35

Nwosu, Victoria Onyeka. "Generation and detection of ultrashort pulses." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1823.

Full text

Abstract:

Thesis (MSc (Physics))--University of Stellenbosch, 2009.
The exciting field of ultrashort laser optics has experienced tremendous growth since it's inception. One of it's branches that has been of continuous interest is the characterization of ultrashort laser pulses ...

APA, Harvard, Vancouver, ISO, and other styles

36

Chen, Zhao S. M. Massachusetts Institute of Technology. "Modeling phonon-polariton generation and control in ferroelectric crystals." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53237.

Full text

Abstract:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 101-109).
In this thesis, we present simulations, using Finite Element Method (FEM), of phonon-polariton generation and coherent control in ferroelectric crystals LiNbO₃ and LiTaO₃ through nonlinear electro-optic interactions with ultrashort laser pulses. This direct space-time monitoring platform is used to investigate the nature of the excitation mechanism, the science of propagation in patterned structure, and the waveform control via multi-dimensional pulse shaping. Compared with previous simulation methods, this platform demonstrates considerable improvement in complex domain by achieving varied accuracy over space based on the level of interest of the region, which may facilitate scientific exploration in high power terahertz generation and polaritonic signal processing.
by Zhao Chen.
S.M.

APA, Harvard, Vancouver, ISO, and other styles

37

Keshet, Aviv. "A next-generation apparatus for lithium optical lattice experiments." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/79254.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, February 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 167-173).
Quantum simulation is emerging as an ambitious and active subfield of atomic physics. This thesis describes progress towards the goal of simulating condensed matter systems, in particular the physics of the Fermi-Hubbard model, using ultracold Lithium atoms in an optical lattice. A major goal of the quantum simulation program is to observe phase transitions of the Hubbard model, into Néel antiferromagnetic phases and d-wave superfluid phases. Phase transitions are generally accompanied by a change in an underlying correlation in a physical system. Such correlations may be most amenable to probing by looking at fluctuations in the system. Experimental techniques for probing density and magnetization fluctuations in a variety of atomic Fermi systems are developed. The suppression of density fluctuations (or atom "shot noise") in an ideal degenerate Fermi gas is observed by absorption imaging of time-of-flight expanded clouds. Intrap measurements of density and magnetization fluctuations are not easy to probe with absorption imaging, due to their extremely high attenuation. A method to probe these fluctuations based on speckle patterns, caused by fluctuations in the index of refraction for a detuned illumination beam, is developed and applied first to weakly interacting and then to strongly interacting in-trap gases. Fluctuation probes such as these will be a crucial tool in future quantum simulation of condensed matter systems. The quantum simulation experiments that we want to perform require a complex sequence of precisely timed computer controlled events. A distributed GUI-based control system designed with such experiments in mind, The Cicero Word Generator, is described. The system makes use of a client-server separation between a user interface for sequence design and a set of output hardware servers. Output hardware servers are designed to use standard National Instruments output cards, but the client-server nature allows this to be extended to other output hardware. Output sequences running on multiple servers and output cards can be synchronized using a shared clock. By using an FPGA-generated variable frequency clock, redundant buffers can be dramatically shortened, and a time resolution of 100ns achieved over effectively arbitrary sequence lengths. Experimental set-ups for producing, manipulating, and probing ultracold atomic gases can be quite complicated. To move forward with a quantum simulation program, it is necessary to have an apparatus that operates with a reliability that is not easily achieved in the face of this complexity. The design of a new apparatus is discussed. This Sodium-Lithium ultracold gas production machine has been engineered to incorporate as much experimental experience as possible to enhance its reliability. Particular attention has been paid to maximizing optical access and the utilization of this optical access, controlling the ambient temperature of the experiment, achieving a high vacuum, and simplifying subsystems where possible. The apparatus is now on the verge of producing degenerate gases, and should serve as a stable platform on which to perform future lattice quantum simulation experiments.
by Aviv Keshet.
Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

38

Bhatia, Nikhil S. "A Physical Layer Implementation of Reconfigurable Radio." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/35926.

Full text

Abstract:

The next generation of wireless communications will demand the use of software radio technology as the basic architecture to support multi-standard, multi-mode and future-proof radio designs. Software-defined radios are configurable devices in which the physical layer can be reprogrammed to support various standards. Field programmable architectures provide a suitable platform to achieve such run-time reconfigurations of the physical layer of the radio. This thesis explores the use of FPGAs in the design of reconfigurable radios. The results presented here demonstrate how FPGAs can be used to provide the flexibility, performance, efficiency and better resource utilization while meeting the speed and area constraints set by a particular design. The partial reconfiguration feature available in the state-of-the art FPGAs has been exploited to implement the baseband physical layer of reconfigurable radio which can be altered to support various modulations schemes for different wireless standards. The design flow for partial reconfiguration along with the implementation results on two different FPGA platforms is presented. The experiments presented in this thesis make use of System Generator for DSP, a productivity tool from Xilinx, to design and to simulate system-level models in a MATLAB/Simulink environment, and to obtain timing and resource utilization results before implementing the design on actual hardware.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

39

Tolic-Nørrelykke, Iva M., Sven K. Vogel, Nenad Pavin, Nicola Maghelli, and Frank Jülicher. "Self-Organization of Dynein Motors Generates Meiotic Nuclear Oscillations." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-180717.

Full text

Abstract:

Meiotic nuclear oscillations in the fission yeast Schizosaccharomyces pombe are crucial for proper chromosome pairing and recombination. We report a mechanism of these oscillations on the basis of collective behavior of dynein motors linking the cell cortex and dynamic microtubules that extend from the spindle pole body in opposite directions. By combining quantitative live cell imaging and laser ablation with a theoretical description, we show that dynein dynamically redistributes in the cell in response to load forces, resulting in more dynein attached to the leading than to the trailing microtubules. The redistribution of motors introduces an asymmetry of motor forces pulling in opposite directions, leading to the generation of oscillations. Our work provides the first direct in vivo observation of self-organized dynamic dynein distributions, which, owing to the intrinsic motor properties, generate regular large-scale movements in the cell.

APA, Harvard, Vancouver, ISO, and other styles

40

Coleman, Christopher Lamar 1971. "Computer-generated holograms for free-space optical interconnects." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282593.

Full text

Abstract:

This dissertation describes an investigation into the use of computer generated holograms to implement free-space optical interconnects. Computer generated holograms are discussed in terms of their theory of operation, design principles, fabrication techniques, optical performance, and sources of error. To motivate the research, discussion of an optoelectronic computing module is included; the device uses computer generated holograms to implement large-fanout optical interconnects. The emphasis of this dissertation is not on a specific application, rather it is focused on understanding the abilities and limitations of computer generated holograms. New contributions are made in the area of hologram design, both individual and multifaceted elements. These design techniques were built into a computer aided design tool (SPIDER 3.0), which was developed to promote the use of computer generated holograms. Hologram fabrication techniques and optical performance are also carefully characterized. Measurements show that performance is poorer than what is expected. Several significant sources of error are identified in the design and fabrication of computer generated holograms, and these effects are shown to explain most of the measured results. The dissertation concludes that computer generated holograms are currently limited by errors in fabrication and in the approximate diffraction theories employed in the design process. While the optical performance of the holograms is not as good as expected, the results are shown to be adequate for successful use in real applications.

APA, Harvard, Vancouver, ISO, and other styles

41

Henestroza, Enrique. "Generation, transport and focusing of high-brightness heavy ion beams." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37211.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.
Includes bibliographical references (p. 195-201).
The Neutralized Transport Experiment (NTX) has been built at the Heavy Ion Fusion Virtual National Laboratory. NTX is the first successful integrated beam system experiment that explores various physical phenomena, and determines the final spot size of a high intensity ion beam on a scaled version of a Heavy Ion Fusion driver. The final spot size is determined by the conditions of the beam produced in the injector, the beam dynamics in the focusing lattice, and the plasma neutralization dynamics in the final transport. A high brightness ion source using an aperturing technique delivers 25 mA of single charged potassium ion beam at 300 keV and a normalized edge emittance of 0.05 r-mm-mr. The ion beam is injected into a large bore magnetic quadrupole lattice, which produces a 20 mm radius beam converging at 20 mr. The converging ion beam is further injected into a plasma neutralization drift section where it is compressed ballistically down to a 1 mm spot size.
(cont.) NTX provides the first experimental proof of plasma neutralized ballistic transport of a space-charge dominated ion beam, the information about higher order aberration effects on the spot size, the validation of numerical tools based on excellent agreement between measurements and numerical simulations over a broad parameter regime, and the development of new diagnostics to study the ion beam dynamics. The theoretical and experimental results are presented on the beam dynamics in the ion diode, downstream quadrupole lattice, and final neutralized transport.
by Enrique Henestroza.
Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

42

Lu, Xueying Ph D. Massachusetts Institute of Technology. "Metamaterial structures for Wakefield acceleration and high power microwave generation." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123347.

Full text

Abstract:

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 209-218).
This thesis presents the theoretical and experimental investigation of the interaction of metamaterial structures with electron beams for two applications: wakefield acceleration and high power microwave generation. Under the topic of wakefield acceleration, on the theoretical side, several metamaterial structures have been designed and simulated. The novel phenomenon of reversed Cherenkov radiation has been found to enhance the beam-wave interaction in metamaterials. A metallic wagon wheel metamaterial structure was designed and built for use in an experiment at the Argonne Wakefield Accelerator (AWA) Facility. On the experimental side, this thesis presents the first demonstration of high-power, reversed Cherenkov wakefield radiation by short electron bunches passing through the wagon wheel structure at the AWA. Single 45 nC electron bunches of 65 MeV energy traversing the structure generated up to 25 MW in 2 ns pulses at 11.4 GHz, in excellent agreement with theory.
Two bunches of 85 nC with appropriate temporal spacing generated up to 80 MW by coherent wakefield superposition. If this power were applied to a trailing witness bunch in a collinear wakefield accelerator, it would provide an accelerating gradient of 75 MV/m. Under the topic of high power microwave generation, on the theoretical side, an analytical theory has been developed to predict the novel Cherenkov-cyclotron interaction in metamaterial-based microwave devices. An S-band metamaterial-loaded waveguide with reverse symmetry has been designed and built to work with the Cherenkov-cyclotron interaction. On the experimental side, this thesis presents the experimental results of the metamaterial-loaded waveguide built at MIT. Power levels to 2.9 MW at 2.4 GHz in full 1 [mu]s pulses were generated by an electron beam of up to 490 kV of voltage and 84 A of current.
Frequency tuning measurements verified that pulses above 1 MW of output power were only seen in the Cherenkov-cyclotron mode. With these results, this thesis demonstrates the unique features of metamaterial structures that are very attractive for high-gradient wakefield accelerators and high power microwave sources. Advantages include the high shunt impedance for intense beam-wave interaction; the simple and rugged structure; and a large parameter space for various optimization goals
by Xueying Lu.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Physics

APA, Harvard, Vancouver, ISO, and other styles

43

Yu, Jefferey C. H. "Collinear acousto-optic interactions in optical fibers using laser generated flexural acoustic waves." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61782.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Zhang, Hao Ph D. Massachusetts Institute of Technology. "Generation and Measurement of Entangled Atomic Ensembles with an Optical Cavity." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103221.

Full text

Abstract:

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-109).
Atomic interferometers have a resolution limit set by the projection noise in measurements on ensembles of uncorrelated atoms. To overcome this classical limit and extend precision measurements into the quantum regime, we need to generate complex entangled states of large atomic ensembles and measure the atomic states with high-quality detection. This thesis describes two experiments in this context. The first experiment demonstrates single-atom resolution and detection sensitivity more than 20 dB below the projection noise limit for hyperfine-state-selective measurements on mesoscopic ensembles containing 100 or more atoms. The measurement detects the atom-induced shift of the resonance frequency of an optical cavity containing the ensemble. The second experiment generates entangled states of 3,000 atoms with non-Gaussian spin distributions. Atoms interact with a weak cavity field, and the heralded detection of a single photon with certain polarization prepares the entangled states. By measuring the non-Gaussian spin distributions using the atom-cavity interaction, we construct a negative Wigner function, manifestly demonstrating that the atoms are entangled. We also show that nearly all of 3000 atoms are involved in the entanglement using an entanglement measure known as the entanglement depth.
by Hao Zhang.
Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

45

Hu, Wen 1968. "Generation of coherent high-power microwave radiation with relativisitic electron beams." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28102.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Mookerji, Bhaskar. "Generation of fiber-coupled, nondegenerate, polarization-entangled photons for quantum communication." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51594.

Full text

Abstract:

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.
Page 42 blank.
Includes bibliographical references.
The production of polarization-entangled photon pairs from spontaneous parametric downconversion (SPDC) enables many applications of quantum information processing. In this thesis, we use type-0 phase-matched downconversion of pump photons from a 532 nm continuous-wave laser to generate 798 nm signal and 1.6 tim idler photon pairs in periodically-poled, congruent lithium niobate (PPLN). Difference frequency generation of 798 nm is used for characterizing PPLN, including phase matching bandwidth and effective nonlinear coefficient. Optimal focusing for generating a single spatial mode SPDC output allows efficient coupling of signal and idler photons. Through coincidence counting, our source's spectral brightness is measured to be 3.6 x 105 Hz/mW/nm detected pairs/s/mW of pump power per nm of output photon bandwidth with an idler conditional detection efficiency of 1.6%. This work is a significant first step toward realizing a high-flux source of nondegenerate polarization-entangled photons.
by Bhaskar Mookerji.
S.B.

APA, Harvard, Vancouver, ISO, and other styles

47

Yakovleva, Elizaveta. "Dark Photon decay generated by muons in the SHiP experiment." Thesis, Uppsala universitet, Institutionen för materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414520.

Full text

Abstract:

This project has investigated the muon background of the SHiP experiment to determine whether it can boost the experiment sensitivity to visible Dark Photon decay. Using Fermi-Weizsäcker-Williams approximation to muon scattering we found the probability of muons generating massive photons, using Bremsstrahlung and direct lepton pair production as an estimation of the frequency of muon EM-interactions. In this work we only considered muons with momenta above 10 GeV/c. The number of visible Dark Photon decays was calculated for a range of the coupling constant and photon mass. The resulting range that promised visible decay has already been excluded by previous experiments, but the method could be used to further investigate enhanced production of Dark Photons from muons and electrons, and possibly also production of Axion-like particles. The work could also be used to estimate sensitivities of other experiments using muons.

APA, Harvard, Vancouver, ISO, and other styles

48

Tabard-Cossa, Vincent. "Microcantilever actuation generated by redox-induced surface stress." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102214.

Full text

Abstract:

Electrochemically-induced changes in surface stress at the solid-liquid interface are measured using a differential cantilever-based sensor. The simultaneous, in situ measurements of the current (charge) and interfacial stress changes are performed by employing an AFM cantilever as both the working electrode (in a conventional three-probe electrochemical cell configuration) and as the mechanical transducer (bending of the cantilever). The custom-built instrument achieves a surface stress sensitivity of 1x10-4 N/m and a dynamic range of 5x105. Combining electrochemistry with cantilever-based sensing provides the extra surface characterization capability essential for the interpretation of the origin of the surface stress.
The objective of the present study is to gain a better understanding of the mechanisms responsible for the nanomechanical motion of cantilever sensors during adsorption and absorption processes. The study of these simple model systems will lead to a general understanding of the cantilever-based sensor's response and provide insights into the physical origin of the measured surface stress.
The surface stress generated by the electrochemically-controlled absorption of ions into a thin polypyrrole film is investigated. A compressive change in surface stress of about -2 N/m is measured when the polymer is electrochemically switched between its oxidized and neutral (swollen) state. The volume change of the polymer phase with respect to the gold-coated cantilever is shown to be responsible for the mechanical motion observed.
The potential-induced surface stress and surface energy change on an Au(111)-textured cantilever, in a 0.1 M HClO4 electrolyte, are simultaneously measured. These measurements revealed that for solid electrodes these two thermodynamic parameters are significantly different. In the double layer region, a surface stress change of -0.55 +/-0.06 N/m is measured during ClO4- adsorption whereas the surface energy variation is smaller by one order of magnitude. The origin of the surface stress change at the metal-electrolyte interface is understood by the variation in electron density at the surface which alters the inter-atomic bonds strength between surface atoms, while the specificity of adsorption of ions is found to be mostly responsible for the fine structure of the surface stress profile.

APA, Harvard, Vancouver, ISO, and other styles

49

Sayed, Naeem Ahmad. "Investigation of harmonic generation in laser produced plasmas." Thesis, Royal Holloway, University of London, 1987. http://repository.royalholloway.ac.uk/items/2ef1082d-3365-4226-97b6-1f74da1da3eb/1/.

Full text

Abstract:

A study of harmonic generation in Laser produced plasmas is presented. Experiments were performed on Royal Holloway College's carbon-dioxide laser system and on the Rutherford Appleton Laboratory's neodymium-glass laser facility. Various targets were irradiated. The backscattered radiation was spectrally analysed in the vicinity of the incident(w0) and twice incident frequency(2w0). Optical and x-ray diagnostics were also undertaken. Theoretical models for harmonic generation in laser produced plasmas by Cairns, Erokhin, Silin and others are reviewed and compared to the experimental results. It is shown that theories due to Cairns and Silin give reasonable estimates of plasma temperature, from the experimental shift of the second harmonic (2w), though the former requires the plasma density scale-length to be known to a greater accuracy. However, Cairns explains satisfactorily the observed structure of the second harmonic spectra. Other theories account well for the observed dependence of the intensity of the second harmonic to that incident. Finally, an attempt is made to explain features of the 2w spectrum in terms of plasma motion, resonance absorption, density profile modification and ponderomotive forces.

APA, Harvard, Vancouver, ISO, and other styles

50

Quarterman, Adrian Hugh. "Femtosecond pulse generation in surface-emitting semiconductor lasers." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72535/.

Full text

Abstract:

In this thesis I report significant advances towards the goal of stable ultrashort pulse generation in mode-locked optically pumped vertical external-cavity surface-emitting lasers (VECSELs). Continuous wave VECSELs were first designed as a type of semiconductor laser capable of producing high output power in near transform-limited beams. Optical pumping allows the output power of the device to be increased simply by increasing the pumped area of the sample, and an external cavity forces the laser into single transverse mode operation. VECSELs’ external cavities also allow for the insertion of semiconductor saturable absorber mirrors (SESAMs) for modelocking. Mode-locked VECSELs have surpassed the performance of other types of mode-locked semiconductor laser, with modelocking via the optical Stark effect allowing VECSELs to produce sub-picosecond pulses in transform-limited beams, at power levels up to 100 mW and at GHz repetition rates. The work presented in this thesis describes recent progress in reducing the durations of VECSEL pulses to below 100 fs. At these pulse durations, gain saturation forces the laser oscillator to enter a dynamic regime never before seen in semiconductor lasers, which is also investigated here. In addition, the timing jitter of a VECSEL mode-locked using the optical Stark effect is characterised for the first time, and a versatile frequency-divider-based active stabilisation technique is demonstrated. Finally, the fabrication of carbon nanotube based saturable absorbers for VECSEL modelocking via solution processing is investigated.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Physics generator'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles