Дисертації: "Energy and power density"

1

Lyu, Xiaofeng. "High-Power-Density Converter for Renewable Energy Application." Diss., North Dakota State University, 2017. https://hdl.handle.net/10365/26345.

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Due to the energy crisis and environmental pollution, renewable sources are more and more important. Power electronics technology is widely applied in these emerging applications and its function is to make the power conversion. The efficiency of power converters is very important and also the size of power converters is more and more concerned. Therefore, high efficiency and high power density with little power loss and light weight are a trend for power converters. In this research work, light-emitting diode (LED) drivers are first investigated and advanced concaved current control is applied in AC-DC linear LED drivers, which can achieve high power density and high efficiency for indoor applications. Also, high-power-density single-phase DC-AC inverter with power decoupling function is a very hot topic in Photovoltaic (PV) applications. The research proposed an in-series and in-parallel power decoupling method to minimize the passive dc-link capacitance. Furthermore, an instantaneous pulse power compensator (IPPC) is proposed. When compared with the existing methods, it can achieve higher system power density. Besides, grid-tied controller is designed and tested. What?s more, three-phase inverter is investigated for the segmented motor in electric vehicle (EV) and hybrid electric vehicle (HEV) applications. Interleaved control methods are applied with different control schemes. High-power-density and high-efficiency three-phase inverter systems are compared. Finally, DC-DC switched-tank resonant converter is studied for 48V data center application. The proposed converter can achieve ultra-high efficiency and high power density. The planar inductor is designed and simulated with Maxwell software. The prototype is made and tested.

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2

Briggs, Maxwell H. "Improving Free-Piston Stirling Engine Power Density." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1432660882.

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3

Kang, Byoungwoo. "Designing materials for energy storage with high power and energy density : LiFePO₄ cathode material." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/59707.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2010.
"February 2010." Cataloged from PDF version of thesis.
Includes bibliographical references.
LiFePO₄ has drawn a lot of attention as a cathode material in lithium rechargeable batteries because its structural and thermal stability, its inexpensive cost, and environmental friendliness meet the requirements of power sources for electric vehicles, except high power capability. Strategies to increase the rather sluggish rate performance of bulk LiFePO₄ have focused on improving electron transport in the bulk or at the surface of the material, or on reducing the path length over which the electron and Li* have to move by using nano-sized materials. However, recent evidence indicates LiFePO₄ is pure one dimensional lithium conductor. So, lithium transport is as important as electron transport. Strong anisotropic lithium diffusion results in limited transports of lithium ions in both the bulk and the surface. Reducing the particle size improves the transport of lithium ions in the bulk, and modification of the surface with a lithium-ion conducting material should enhance the transport of lithium ions on the surface. A poorly crystallized lithium phosphate phase on the surface of nanoscale LiFePO₄ is created by using proper off-stoichiometry (LiFeo.9Po.9504.3). The off-stoichiometric strategy leads to small particles less than 50 nm through grain growth restriction and a poorly crystallized lithium phosphate on the surface. The conducting surface phase can not only improve the transport of lithium ions on the surface but also facilitate the access of lithium ions to the surface by reducing anisotropic lithium diffusion on the surface induced by its amorphous nature. The off-stoichiometric material shows extremely high rate performance, achieving reasonable capacity even at 400C (9 s charge/discharge). In this thesis, the main finding is as follows: LiFePO₄ shows fast bulk kinetics and in itself does not limit the rate of charge and discharge. When bulk Li transport is very fast, the battery charging and discharging are limited by other factors such as the surface adsorption and surface transfer of lithium ions and the configuration of a cell. The off-stoichiometric strategy to improve surface transports addresses the right rate-limiting step and reveals the real capability of LiFePO₄.
by Byoungwoo Kang.
Ph.D.

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4

Armutlulu, Andac. "Deterministically engineered, high power density energy storage devices enabled by MEMS technologies." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54270.

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This study focuses on the design, fabrication, and characterization of deterministically engineered, three-dimensional architectures to be used as high-performance electrodes in energy storage applications. These high-surface-area architectures are created by the robotically-assisted sequential electrodeposition of structural and sacrificial layers in an alternating fashion, followed by the removal of the sacrificial layers. The primary goal of this study is the incorporation of these highly laminated architectures into the battery electrodes to improve their power density without compromising their energy density. MEMS technologies, as well as electrochemical techniques, are utilized for the realization of these high-power electrodes with precisely controlled characteristic dimensions. Diffusion-limited models are adopted for the determination of the optimum characteristic dimensions of the electrodes, including the surface area, the thickness of the active material film, and the distance between the adjacent layers of the multilayer structure. The contribution of the resultant structures to the power performance is first demonstrated by a proof-of-concept Zn-air microbattery which is based on a multilayer Ni backbone coated with a conformal Zn film serving as the anode. This primary battery system demonstrates superior performance to its thin-film counterpart in terms of the energy density at high discharge rates. Another demonstration involves secondary battery chemistries, including Ni(OH)2 and Li-ion systems, both of which exhibit significant cycling stability and remarkable power capability by delivering more than 50% of their capacities after ultra-fast charge rates of 60 C. Areal capacities as high as 5.1 mAh cm-2 are reported. This multilayer fabrication approach is also proven successful for realizing high-performance electrochemical capacitors. Ni(OH)2-based electrochemical capacitors feature a relatively high areal capacitance of 1319 mF cm-2 and an outstanding cycling stability with a 94% capacity retention after more than 1000 cycles. The improved power performance of the electrodes is realized by the simultaneous minimization of the internal resistances encountered during the transport of the ionic and electronic species at high charge and discharge rates. The high surface area provided by the highly laminated backbone structures enables an increased number of active sites for the redox reactions. The formation of a thin and conformal active material film on this high surface area structure renders a reduced ionic diffusion and electronic conduction path length, mitigating the power-limiting effect of the active materials with low conductivities. Also, the highly conductive backbone serving as a mechanically stable and electrochemically inert current collector features minimized transport resistance for the electrons. Finally, the highly scalable nature of the multilayer structures enables the realization of high-performance electrodes for a wide range of applications from autonomous microsystems to macroscale portable electronic devices.

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5

Nutter, David B. "Sound Absorption and Sound Power Measurements in Reverberation Chambers Using Energy Density Methods." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1546.pdf.

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6

Patankar, Siddharth. "High-power laser systems for driving and probing high energy density physics experiments." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23893.

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This thesis describes the construction of a hybrid OPCPA and Nd:Glass based laser system to provide advanced diagnostic capabilities for the MAGPIE pulsed power facility at Imperial College London. The laser system (named Cerberus) is designed to provide one short pulse 500 fs beam for proton probing and two long pulse beams, one for x-ray backlighting and one for Thomson scattering. The aim of this project is to accurately determine plasma parameters in a range of demanding experimental environments. The thesis is split into two sections; the first section provides details about the design and implementation of the laser system while the latter chapters present experimental data obtained on the MAGPIE facilty. The front end for the laser system is based on optically synchronised Optical Parametric Chirped Puled Amplification (OPCPA) which is supplemented by large aperture flashlamp pumped Nd:Glass power amplifiers in the latter stages to increase the energy to the Joule level. The use of optical parametric amplifiers (OPAs) in the pre-amplifier stages reduces gain narrowing, B-integral and improves contrast. Simulations of the dispersive optics for the Chirped Pulse Amplification (CPA) system are described in detail. Spatially resolved Thomson scattering was used to measure temperature and velocity of ablation streams in aluminium and tungsten cylindrical wire arrays. The measurements show a peak ow velocity of 120 km/s and agree well with 3D MHD simulations for the case of aluminium. There is discrepancy with the tungsten data caused by the difficulty in handling of collisionality calculations. Novel data showing the self-emission of ions from tungsten radial wire arrays is presented as a key step towards laser driven proton probing of MAGPIE. It is observed that the bulk of the emission corresponds to low energy protons with energies of ~ 100 keV. Protons with energy > 600 keV were observed to emanate from the collapsing magnetic jet using a coded aperture camera. These results offer interesting new prospects in diagnosing wire arrays.

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7

Dinca, Dragos. "Development of an Integrated High Energy Density Capture and Storage System for Ultrafast Supply/Extended Energy Consumption Applications." Cleveland State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=csu1495115874616384.

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8

Adamson, Jesse Timothy. "Pulse Density Modulated Soft Switching Cycloconverter." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/315.

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Single stage cycloconverters generally incorporate hard switching at turn on and soft switching at turn off. This hard switching at turn on combined with the slow switching speeds of thyristors (the switch of choice for standard cycloconverters) limits their use to lower frequency applications. This thesis explores the analysis and design of a pulse density modulated (PDM), soft switching cycloconverter. Unlike standard cycloconverters, the controller in this converter does not adjust thyristor firing angles. It lets only complete half cycles of the input waveform through to the output. This allows and requires a much greater frequency step down from the input to the output. The advantages, shortcomings and tradeoffs of this topology are explored as this converter is designed, built and tested. The resulting cycloconverter has many deficiencies, but proves the concept of the PDM soft switching technique. Cases for further improvement and study are outlined. In the end, this converter shows much promise for applications requiring a high step down in frequency, as well as where the lower electromagnetic interference (EMI) of soft switching may be beneficial.

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9

Amin, Mahmoud. "Efficiency and Power Density Improvement of Grid-Connected Hybrid Renewable Energy Systems utilizing High Frequency-Based Power Converters." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/600.

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High efficiency of power converters placed between renewable energy sources and the utility grid is required to maximize the utilization of these sources. Power quality is another aspect that requires large passive elements (inductors, capacitors) to be placed between these sources and the grid. The main objective is to develop higher-level high frequency-based power converter system (HFPCS) that optimizes the use of hybrid renewable power injected into the power grid. The HFPCS provides high efficiency, reduced size of passive components, higher levels of power density realization, lower harmonic distortion, higher reliability, and lower cost. The dynamic modeling for each part in this system is developed, simulated and tested. The steady-state performance of the grid-connected hybrid power system with battery storage is analyzed. Various types of simulations were performed and a number of algorithms were developed and tested to verify the effectiveness of the power conversion topologies. A modified hysteresis-control strategy for the rectifier and the battery charging/discharging system was developed and implemented. A voltage oriented control (VOC) scheme was developed to control the energy injected into the grid. The developed HFPCS was compared experimentally with other currently available power converters. The developed HFPCS was employed inside a microgrid system infrastructure, connecting it to the power grid to verify its power transfer capabilities and grid connectivity. Grid connectivity tests verified these power transfer capabilities of the developed converter in addition to its ability of serving the load in a shared manner. In order to investigate the performance of the developed system, an experimental setup for the HF-based hybrid generation system was constructed. We designed a board containing a digital signal processor chip on which the developed control system was embedded. The board was fabricated and experimentally tested. The system’s high precision requirements were verified. Each component of the system was built and tested separately, and then the whole system was connected and tested. The simulation and experimental results confirm the effectiveness of the developed converter system for grid-connected hybrid renewable energy systems as well as for hybrid electric vehicles and other industrial applications.

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10

Signorelli, Riccardo (Riccardo Laurea). "High energy and power density nanotube-enhanced ultracapacitor design, modeling, testing, and predicted performance." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/63027.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 161-164).
Today's batteries are penalized by their poor cycleability (limited to few thousand cycles), shelf life, and inability to quickly recharge (limited to tens of minutes). Commercial ultracapacitors are energy storage systems that solve these problems by offering more than one million recharges with little capacitance degradation, recharge times on the order of few seconds, and unlimited shelf life. However, today's ultracapacitors are limited by their low energy stored per unit of volume and weight (5% that of a lithium ion battery), and their high cost (ten times greater than that of lithium ion batteries) per unit of energy stored. This thesis presents vertical carbon nanotubes-based electrodes designed to achieve, when packaged into an ultracapacitor cell, a four to seven times higher power density (7.8 kW/1) and a five times higher energy density (31 Wh/1) than those of activated carbon-based ultracapacitors. Models to predict the energy density, power density, and efficiency of an ultracapacitor cell using vertical carbon nanotube electrodes of a given morphology are described. The synthesis of carbon nanotube electrodes fabricated on thin conducting substrates of tungsten and aluminum that have the target nanotube average diameters and lengths is described along with insights on the thermodynamics of the nanotube growth reaction. The low pressure chemical vapor deposition reactor used to fabricate nanotube electrodes on conducting substrates is described. Electrochemical measurements of electrodes are presented to corroborate electrochemical modeling leading to the performance prediction of carbon nanotube-based ultracapacitors. Finally, some key remaining questions to further advance the understanding of nanotubes as electrode materials for ultracapacitor are presented.
by Riccardo Signorelli.
Ph.D.

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11

Marquez, Daniel Ryan. "Estimating the Acoustic Power of Sources in Nonideal Enclosures Using Generalized Acoustic Energy Density." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/3977.

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Sound power measurements of acoustic sources are generally made in reverberation or anechoic chambers using acoustic pressure measurements as outlined in specific ISO or other standards. A reverberation chamber produces an approximate diffuse-field condition, wherein the sound power is determined from the spatially averaged squared pressure. An anechoic chamber produces an approximate free-field condition, wherein the sound power is estimated from squared pressure over an enveloping measurement surface. However, in many cases it is desirable to estimate sound power within nonideal semi-reverberant spaces. In these environments, both direct and reverberant energies may contribute significantly to the total acoustic field. This paper introduces two measurement methods that utilize a weighted combination of potential and kinetic energy densities, known as generalized acoustic energy density, to estimate sound power in nonideal semi-reverberant rooms. The first method employs a generalized sound power formulation, which is an adaptation to an equation developed in 1948 for semi-reverberant spaces. The second, called the two-point in situ method, is a technique based on the generalized sound power formulation for quick and accurate in situ sound power estimates. Since the generalized acoustic energy density is more spatially uniform than the squared acoustic pressure in an enclosed field, these methods have the advantage of achieving the same accuracy in sound power determination with fewer measurement positions. This thesis explores the possibility of using these new methods in place of methods outlined in current ISO standards by describing analytical, numerical, and experimental results.

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12

Patil, Sandeep Kesharsingh. "Modeling and simulations of diphasic composites for development of high energy density dielectrics." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Patil_09007dcc804e35ca.pdf.

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Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 21, 2008) Includes bibliographical references.

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13

Ihrfors, Charlotte. "Binder-free oxide nanotube electrodes for high energy and power density 3D Li-ion microbatteries." Thesis, Uppsala universitet, Strukturkemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-227451.

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This thesis covers synthesis and characterisation of TiO2 nanotubes and TiO2 / Li4Ti5O12 composite nanotubes. The aim was to build batteries with high areal capacity and good rate capability. TiO2 nanotubes were synthesized by two step anodization of titanium metal foil and the composite electrodes were synthesized through electrochemical lithiation of TiO2 nanotubes. To improve the battery performance the TiO2 nanotubes were annealed at 350 °C in air atmosphere, while the composite electrodes were annealed in argon at 550 °C. The longest TiO2 nanotubes were measured to 42.5 μm. The 40 μm long nanotubes displayed an areal capacity of 1.0 mAh/cm2 and a gravimetric capacity of 89 mAh/g. Nanotubes having a length of 10 μm had an areal capacity of 0.33 mAh/cm2 and a gravimetriccapacity of 130 mAh/g. When cycled at high rates, 10C, the capacity of the 40 μm nanotubes was 0.25 mAh/cm2, using a current density of 9.3 mA. The capacity of the 40 μm long nanotubes were higher than for the 10 μm long, but the increase was not proportional to the increase in length. A composite electrode was successfully synthesized and was found to have a capacity of 0.25 mAh/cm2 at a rate of C/5.

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14

Wang, Ruxi. "High Power Density and High Temperature Converter Design for Transportation Applications." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28264.

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The continual development of high-power-density power electronic converters is driven particularly by modern transportation applications like electrical vehicles and more electric aircraft where the space and carrier capability is limited. However, there are several challenges related to transportation applications such as fault tolerance for safety concern, high temperature operation in extreme environments and more strict electromagnetic compatibility requirement. These challenges will increase difficulties for more electrical system adoption in the transportation applications. In this dissertation, comprehensive methodologies including more efficient energy storage solution, better power electronics devices capability, better packaging performance and more compact EMI filter design are analyzed and proposed for the goal of high power density converter design in transportation applications.
Ph. D.

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15

Hoyt, Travis Nathan. "Improvements to Sound Power Measurements for Large, Extended Sources in Semi-Reverberant Rooms Using Generalized Energy Density." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7597.

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Sound power measurements of acoustic sources are typically performed in anechoic or reverberation chambers using acoustic pressure according to international standards. The anechoic chamber creates a free-field environment where the sound power is estimated from the squared pressure integrated over some enveloping surface. The reverberation chamber produces diffuse-field conditions, where sound power is proportional to the spatially averaged squared pressure. In semi-reverberant environments, the direct and reverberant energies each contribute to the total measured field. If the kinetic and potential components of acoustic energy density are weighted appropriately, the spatial variation of the field can be significantly reduced compared to squared pressure. This generalized energy density allows an adaptation of the sound power formulation by Hopkins and Stryker to be used to make an efficient and accurate in situ sound power estimate of a noise source in a non-ideal acoustical environment. Since generalized energy density optimizes the spatial uniformity of the field, fewer measurement positions are needed compared to traditional standards. However, this method breaks down for sources that are large and extended in nature and considerably underestimates the sound power. This thesis explores the practical limits of this method related to the sound power underestimation. It also seeks to understand the special considerations necessary to achieve accurate, survey-grade sound power data of large, extended noise sources through a laboratory study of custom extended and compact sources. A modified method to accurately and efficiently measure the sound power of large, extended sources is proposed with results.

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16

Breitenbach, Rene. "Development of Free-standing Nanostructured Iron Oxide Electrodes for High Energy and Power Density 3D Li-ion Microbatteries." Thesis, Uppsala universitet, Strukturkemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301338.

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17

Zhu, Zhiguang. "Enzymatic fuel cells via synthetic pathway biotransformation." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/51948.

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Enzyme-catalyzed biofuel cells would be a great alternative to current battery technology, as they are clean, safe, and capable of using diverse and abundant renewable biomass with high energy densities, at mild reaction conditions. However, currently, three largest technical challenges for emerging enzymatic fuel cell technologies are incomplete oxidation of most fuels, limited power output, and short lifetime of the cell. Synthetic pathway biotransformation is a technology of assembling a number of enzymes coenzymes for producing low-value biocommodities. In this work, it was applied to generate bioelectricity for the first time. Non-natural enzymatic pathways were developed to utilize maltodextrin and glucose in enzymatic fuel cells. Three immobilization approaches were compared for preparing enzyme electrodes. Thermostable enzymes from thermophiles were cloned and expressed for improving the lifetime and stability of the cell. To further increase the power output, non-immobilized enzyme system was demonstrated to have higher power densities compared to those using immobilized enzyme system, due to better mass transfer and retained native enzyme activities. With the progress on pathway development and power density/stability improvement in enzymatic fuel cells, a high energy density sugar-powered enzymatic fuel cell was demonstrated. The enzymatic pathway consisting of 13 thermostable enzymes enabled the complete oxidation of glucose units in maltodextrin to generate 24 electrons, suggesting a high energy density of such enzymatic fuel cell (300 Wh/kg), which was several folds higher than that of a lithium-ion battery. Maximum power density was 0.74 mW/cm2 at 50 deg C and 20 mM fuel concentration, which was sufficient to power a digital clock or a LED light. These results suggest that enzymatic fuel cells via synthetic pathway biotransformation could achieve high energy density, high power density and increased lifetime. Future efforts should be focused on further increasing power density and enzyme stability in order to make enzymatic fuel cells commercially applicable.
Ph. D.

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18

Machado, Rogerio Rossi. "Estudo do potencial eólico do pontal do abreu – município de Viamão - RS." reponame:Repositório Institucional da FURG, 2008. http://repositorio.furg.br/handle/1/3489.

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Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2008.
Submitted by Lilian M. Silva (lilianmadeirasilva@hotmail.com) on 2013-04-19T22:26:07Z No. of bitstreams: 1 Estudo Do Potencial Eólico Do Pontal Do Abreu – Município De Viamão - RS.pdf: 3173026 bytes, checksum: 65d094e3a89f3d6f6b5c9bd8fe86c064 (MD5)
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Este trabalho tem por objetivo calcular a energia anual, o FC (fator de capacidade) e o potencial eólico da regiãodo Pontal do Abreu, no município de Viamão no Rio Grande do Sul, para uma instalação contendo umúnico aerogerador do tipo FURLANDER com torre de 100m de altura do cubo, raio do rotor de 50m, potência nominal de 2500kW, velocidade de partida de 3m/s e velocidade de corte de 25m/s. As ferramentas utilizadas no tratamento dos dados levantados foram a planilha Excel e o software WindPro, fazendo um comparativo dos resultados obtidos. Foram usados dois métodos distintos para o cálculo: O método “Measure” baseado nos dados brutos baixados do computador de vento e o método “Weibull” baseado na distribuição de probabilidade de Weibull com parâmetros de escala c de forma k. A densidade de potência a altura do cubo considerada (100m) tem um valor em torno de 500 W/m². A direção predominante do vento é L (leste) seguida de SE (sudeste) e SO (sudoeste). A energia anual calculada fica em torno de 10.000 MWh. O FC para instalação considerada fica em torno de 45%. É apresentada também uma introdução aos principais tópicos que dizem respeito a potencial eólico, cálculos energéticos e parques eólicos.
This work has the finality to calculate the annual energy yield, the capacity factor and the site assessment related to wind potential of Pontal do Abreu, a site located in the town of Viamão, in the state of Rio Grande do Sul, Brazil based upon a study with a single Wind Generator Fuhrlaender Model FL2500 100. The chosen Wind Generator has a hub height on 100 m and a rotor diameter of 100 m too that is well fitted for wind characteristics found in this region, cut in wind speed of 3 m/s and a cut out wind speed of 25m/s. The used tools toperform the studies to do wind data site investigation were the Excel spreadsheet and the software Wind Pro. A comparison of results with both soft wares was documented. It was used two methods in the calculations: The method “Measure” based on row data read from a data logger installed on siteand the method “Weibull” that use a scale factor and a shape factor to define the distribution function that better represent the wind speed measure. The power density at the considered hub height(100m) was found to be 500 W/m². The predominant wind directions in the site are E (East), followed by SE (Southeast) and SO (Southwest) according data collect from wind vanes and register on data logger. The energy yield computed by both methods is about 10000 MWh. The Capacity Factor assessed by data is around 45%. There are presented an introduction of mean topics related to wind potential,energy yield findings and wind farms projects.

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19

Rocco, Davide. "Design and impacts of high power density DC-DC converter in automotive powertrain: a methodological approach." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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This thesis work was realized in collaboration with HPE Coxa provider of engineering services and precision manufacturing for automotive, motorsport, automation solution, aerospace and defense sectors. Specifically, this work has been carried out inside the company Control and System Engineering Department. The aim of this work is to describe a methodological approach for the design of an High Density Power DC-DC Converter for high performance electric powertrain and to describe the dependency that exist between system design and performance indicator and which are the consideration that have to be done by the engineers during design phase, following the System Engineering workflow. In order to achieve this purpose, Model-Based Design approach has been used to realize a simulation framework that allow to analyse the overall electric propulsion system behaviour and extract all the data that allow to evaluate the system performance. Specifically, taking into account a real Mission Profile, with Matlab and Simulink tools, the behaviour of the system and the related energy transfer during vehicle acceleration and regenerative breaking phase has been simulated. Thanks to these analysis the requirement for the converter was established and with the support of Electric Simulation Tools, it has been designed the electrical architecture of specific converter. In order to optimize the energy managment phase, a Four-Phase Bidirectional Interleaved architecture has been selected. Moreover it has been highlighted the main aspects related to the integration of the converter in the powertrain system in terms of structural and thermal features.

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20

Masti, Robert Leo. "The Effect of Anomalous Resistivity on the Electrothermal Instability." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103737.

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The current driven electrothermal instability (ETI) forms when the material resistivity is temperature dependent, occurring in nearly all Z-pinch-like high energy density platforms. ETI growth for high-mass density materials is predominantly striation form which corresponds to magnetically perpendicular mode growth. The striation form is caused by a resistivity that increases with temperature, which is often the case for high-mass density materials. In contrast, low-density ETI growth is mainly filamentation form, magnetically aligned modes, because the resistivity tends to decrease with temperature. Simulating ETI is challenging due to the coupling of magnetic field transport to equation of state over a large region of state space spanning solids to plasmas. This dissertation presents a code-code verification study to effectively model the ETI. Specifically, this study provides verification cases which ensure the unit physics components essential to modeling ETI are accurate. This provides a way for fluid-based codes to simulate linear and nonlinear ETI. Additionally, the study provides a sensitivity analysis of nonlinear ETI to equation of state, vacuum resistivity, and vacuum density. Simulations of ETI typically use a collisional form of the resistivity as provided, e.g., in a Lee-More Desjarlais conductivity table. In regions of low-mass density, collision-less transport needs to be incorporated to properly simulate the filamentation form of ETI growth. Anomalous resistivity (AR) is an avenue by which these collision-less micro-turbulent effects can be incorporated into a collisional resistivity. AR directly changes the resistivity which will directly modify the linear growth rate of ETI, so a new linear growth rate is derived which includes AR's added dependency on current density. This linear growth rate is verified through a filamentation ETI simulation using an ion acoustic based AR model. Kinetically based simulations of vacuum contaminant plasmas provide a physical platform to study the use of AR models in pulsed-power platforms. Using parameters from the Z-machine pulsed-power device, the incorporation of AR can increase a collisional-based resistivity by upwards of four orders of magnitude. The presence of current-carrying vacuum contaminant plasmas can indirectly affect nonlinear ETI growth through modification of the magnetic diffusion wave. The impact of AR on nonlinear ETI is explored through pulsed-power simulations of a dielectrically coated solid metallic liner surrounded by a low-density vacuum contaminant plasma.
Doctor of Philosophy
High-energy-density physics (HEDP) is the study of materials with pressures that exceed 1Mbar, and is difficult to reach here on Earth. Inertial confinement fusion concepts and experiments are the primary source for achieving these pressures in the laboratory. Inertial confinement fusion (ICF) is a nuclear fusion concept that relies on the inertia of imploding materials to compress a light fuel (often deuterium and tritium) to high densities and temperatures to achieve fusion reactions. The imploding materials in ICF are driven in many ways, but this dissertation focuses on ICF implosions driven by pulsed-power devices. Pulsed-power involves delivering large amounts of capacitive energy in the form of electrical current over very short time scales (nanosecond timescale). The largest pulsed-power driver is the Z-machine at Sandia National Laboratory (SNL) which is capable of delivering upwards of 30 MA in 130 ns approximately. During an ICF implosion there exists instabilities that disrupt the integrity of the implosion causing non-ideal lower density and temperature yields. One such instability is the Rayleigh-Taylor instability where a light fluid supports a heavy fluid under the influence of gravity. The Rayleigh-Taylor is one of the most detrimental instabilities toward achieving ignition and was one of the main research topics in the early stages of this Ph.D. The study of this instability provided a nice intro for modeling in the HEDP regime, specifically, in the uses of tabulated equations-of-state and tabulated transport coefficients (e.g., resistivity and thermal conductivity). The magneto Rayleigh-Taylor instability occurs in pulsed-power fusion platforms where the heavy fluid is now supported by a magnetic field instead of a light fluid. The magneto Rayleigh-Taylor instability is the most destructive instability in many pulsed-power fusion platforms, so understanding seeding mechanisms is critical in mitigating its impact. Magnetized liner inertial fusion (MagLIF) is a pulsed-power fusion concept that involves imploding a solid cylindrical metal annulus on laser-induced pre-magnetized fuel. The solid metal liners have imperfections and defects littered throughout the surface. The imperfections on the surface create a perturbation during the initial phases of the implosion when the solid metal liner is undergoing ohmic heating. Because a solid metal has a resistivity that increases with temperature, as the metal heats the resistivity increases causing more heating which creates a positive feedback loop. This positive feedback loop is similar to the heating process in a nichrome wire in a toaster, and is the fundamental bases of the main instability studied in this dissertation, the electrothermal instability (ETI). ETI is present in all pulsed-power fusion platforms where a current-carrying material has a resistivity that changes with temperature. In MagLIF, ETI is dominant in the early stages of a current pulse where the resistivity of the metal increases with temperature. An increasing resistivity with temperature is connected to the axially growing modes of ETI which is denoted as the striation form of ETI. Contrary to the striation form of ETI, the filamentation form of ETI occurs when resistivity decreases with temperature and is associated with the azimuthally growing modes of ETI. Chapter 2 in this dissertation details a study of how to simulate striaiton ETI for a MagLIF-like configuration across different resistive magnetohydrodynamics (MHD) codes. Resistivity that decreases with temperature typically occurs in low-density materials which are often in a gaseous or plasma state. Low density plasmas are nearly collision-less and have resistivity definitions that often overestimate the conductivity of a plasma in certain experiments. Anomalous resistivity (AR) addresses this overestimation by increasing a collisional resistivity through micro-turbulence driven plasma phenomenon that mimic collisional behavior. The creation of AR involves reduced-modeling of micro-turbulence driven plasma phenomenon, such as the lower hybrid drift instability, to construct an effective collision frequency based on drift speeds. Because AR directly modifies a collisional resistivity for certain conditions, it will directly alter the growth of ETI which is the topic of Chapter 3. The current on the Z-machine is driven by the capacitor bank through the post-hole convolute, the magnetically insulated transmission lines, and then into the chamber. Magnetically insulated transmission lines have been shown to create low-density plasma through desorption processes in the vacuum leading to a load surrounded by a low-density plasma referred to as a vacuum contaminant plasmas (VCP). VCP can divert current from the load by causing a short between the vacuum anode and cathode gap. In simulations, this plasma would be highly conducting when represented by a collisionally-based resistivity model resulting in non-physical vacuum heating that is not observed in experiments. VCP are current-carrying low-density and high-temperature plasmas which make them ideal candidates to study the role of AR as described in Chapter 4. Chapter 4 investigates the role AR in a VCP would have on striation ETI for a MagLIF-like load.

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21

Ma, Xiaohua Ph D. Massachusetts Institute of Technology. "Understanding and designing high power and high energy density cathode materials for lithium ion batteries by experiments and first principles computations." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/101862.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references.
A new layered compound LiNi2/3Sb1/30 2 was synthesized and tested electrochemically to understand the effect of the transition metals on the structural stability of the layered compound upon Li de-intercalation. The electrochemical results show that the structure of LiNi2/3Sb1 /302 degrades upon cycling. XRD pattern refinement and TEM diffraction on the cycled LiNi2/3 Sb1/3O2 indicate that the structure degradation is associated with the migration of Ni into the Li layer. First principles calculation also shows a very low barrier for the migration of a divalent Ni from the transition metal layer to the tetrahedral sites of the lithium layer in the partially delithiated Li2/3Ni2/3Sbl/3O2. The divalent Ni becomes highly mobile because of the strong electrostatic repulsion from the surrounding three Ni3+ and three Sb5+. The effect of the alkali ions on the structural stability in the layered AMO 2 (A = alkali ion; M = transition metals) compounds is discussed by comparing layered LiMnO2 and NaMnO2. The structure of layered LiMnO 2 transforms rapidly into a spinel-like structure upon delithation due to the formation of a Li/Mn dumbbell configuration. However, such kind of dumbbell does not form in NaxMnO2, indicating its better structural stability upon deintercalation. The electrochemical results of NaMnO 2 show a much better capacity retention than that of LiMnO2, confirming that NaMnO2 is more stable than LiMnO2 upon deintercalation. The XRD results of the cycled NaMnO2 also show no significant structural change. The pronounced voltage steps and plateaus of NaMnO2 upon cycling were also investigated. First principles calculations show that the Li diffusivity in LiNi0.5Mn5O4 is in the order of 10-9 cm 2/s, implying that LiNi0.5Mn1.5O4 can be a high rate material even with a large particle size. The electrochemical tests of the micron-sized LiNiO0.5Mn1.5O4 show higher rate capability than nano LiNi0.5Mn1.5O4 by Shaju, et al, indicating that the ionic and electronic transport may not be the rate limiting factors. It was also found that cell configurations, such as separators, mechanical pressure of the cell and the carbon content in the electrode, could dramatically affect the rate capability of the cell. When the cell is highly optimized in configuration, more than half of the theoretical capacity is obtained at a discharge rate of 167C (corresponding to 22 seconds) with a particle size in the range of 3-5 [mu]m, which agrees with the high Li diffusivity by my calculation.
by Xiaohua Ma.
Ph. D.

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22

Pereira, Rosana Aparecida. "Avaliação da microdureza de resina composta polimerizada com fontes de luz halógena e LED, em função da densidade de energia luminosa irradiada." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/25/25131/tde-22102009-103040/.

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No presente estudo, avaliou-se a microdureza da resina composta Z250 (3M ESPE), quando ativada em diferentes tempos (s), diferentes densidades de potência (mW/cm²), em relação à quantidade de energia irradiada (8, 12 e 16 J/cm²), com a finalidade de estabelecer uma densidade de energia luminosa mínima capaz de polimerizar adequadamente os compósitos. Foi utilizado um aparelho com fonte de luz halógena Degulux-Degussa, com 600 mW/cm² e dois aparelhos de fonte de luz LED, Ultraled XP (Dabi-Atlante) com 150 mW/cm² e LED Ultrablue-IS (DMC) com 300 mW/cm² e 600 mW/cm². Duas matrizes bipartidas de PTFE, de 1 e de 2 mm de espessura e um orifício central de 5 mm de diâmetro, foram usadas para confeccionar 60 corpos-de-prova, 5 em cada grupo. As duas partes da matriz foram contidas em um anel metálico com as mesmas espessuras. O material foi inserido na matriz e fotoativado de acordo com os diferentes tempos e a quantidade de densidade de energia luminosa para cada fonte de luz. Para obter os valores de microdureza Knoop, os espécimes foram levados ao microdurômetro Shimadzu HMV-2, com carga estática de 300 g por 5 segundos, para aferir as superfícies exposta (topo) e oposta (base) à fonte de luz, totalizando 120 medições. Os resultados foram submetidos aos testes ANOVA e Tukey, com nível de significância de 5%. Com os dados obtidos foi possível concluir que, com valores a partir de 16 J/cm² e 12 J/cm² de densidade de energia luminosa, espessuras de 2 mm de resina composta podem ser adequadamente polimerizadas utilizando-se fonte de luz halógena (600 mW/cm²) e LED (a partir de 300 mW/cm²) respectivamente. Contudo, estudos clínicos adicionais ainda são necessários para complementar este estudo
At this study it was evaluated the microhardness of the Z250 (3M ESPE) resin composite, when light cured for different periods of time (s), with different power densities (mW/cm²), related to the irradiated luminous energy density (8 J/cm², 12 J/cm² and 16 J/cm²), in order to establish a minimal energy density capable of adequately polymerize the composites. One halogen light curing unit Degulux- Degussa, with 600 mW/cm² of power density and two light-emitting diodes curing units Ultraled XP (Dabi-Atlante) with 150 mW/cm² and LED Ultrablue-IS (DMC) with 300 mW/cm² and 600 mW/cm² were used. Two bipartite PTFE matrices, with 1 and 2 mm of depth and a central orifice of 5 mm diameter, were used to make 60 specimens, 5 per group. The halves of the matrix were positioned inside a brass ring with both depths to prepare the specimens. The resin composite was inserted and light-activated according to the different periods and energy densities of each lightcuring unit. To evaluate Knoop microhardness, specimens were taken to a microdurometer Shimadzu HMV-2 with a static load of 300 g for 5 seconds, evaluating both exposed to light (surface) and opposite to light (base) exposition surfaces, totalizing 120 measurements. Results were submitted to ANOVA and Tukeys test with 5% significance level. Based on the obtained results, it was concluded that, starting from 16 J/cm² and 12 J/cm² of energy luminous density, 2 mm depth resin composite can be adequately polymerized utilizing halogen (600 mW/cm²) and LED ( starting from 300 mW/cm²) curing-units respectively. However, additional clinical studies are necessary to complement this investigation.

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23

Shaheen, Mohammed Mahmoud Zaki Mohammed. "Design and Assessment of Vertical Axis Wind Turbine Farms." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439306478.

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24

Natarajan, Hariharan. "Post occupancy energy analysis of the Gwinnett Environmental and Heritage Center." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41214.

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25

Fogleman, Myles. "Cold X-ray Effects on Satellite Solar Panels in Orbit." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6065.

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An exo-atmospheric nuclear detonation releases up to 80 percent of its’ energy as X-rays. Satellite’s solar cells and their protective coatings are vulnerable to low energy X-ray radiation. Cold X-rays (~1-1.5 keV) are absorbed close to the surface of materials causing the blow-off and rapid formation of Warm Dense Plasmas (WDPs), particularly in a gap between the unshielded active elements of solar cells. To understand how WDPs are created, it is necessary to investigate the power density distribution produced by cold X-rays for typical solar panel surface materials. The Monte Carlo stepping model implemented in the GEANT4 software toolkit is utilized to determine the power density created by cold X-rays in a multi-layered target composed of a layer of an active cell shielded by layers of cover glass and anti-reflective coating. The power density generated by cold X-rays in the unshielded semiconductor layer at different incidence angles is also investigated in order to account for different orientations of the satellite’s solar panels with respect to the point of nuclear detonation. The flux spectrum of X-rays originating from a nuclear blast is described by the Planck's blackbody function with the temperature from 0.1 keV to 10 keV. The secondary radiation (photo-electrons, fluorescence photons, Auger- and Compton-electrons) resulting from absorption and scattering of primary X-rays is taken into account in the redistribution of energy deposition within slabs. The profiles of power density within the slab system produced by primary cold X-rays, secondary photons and electrons are calculated as a function of depth. The discontinuity in power density profiles is observed at the interfaces of slabs due to discrete changes in stopping power between slab materials. The power density is found to be higher in slab materials with higher mass density. The power density profiles are then used in the atomistic Momentum Scaling Model (MSM) coupled with the Molecular Dynamics (MD) method (MSM-MD) to predict the spatiotemporal evolution of WDP in vacuum. The spatial and temporal distribution of density and temperature fields of expanding WDP is evaluated from the MSM-MD simulations. These modeling results provide insights into the underlining physics of the formation and spatiotemporal evolution of WDPs induced by cold X-rays.

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26

Hlongwa, Ntuthuko Wonderboy. "Thermochemical Storage and Lithium Ion Capacitors Efficiency of Manganese-Graphene Framework." University of the Western Cape, 2018. http://hdl.handle.net/11394/6458.

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Philosophiae Doctor - PhD (Chemistry)
Lithium ion capacitors are new and promising class of energy storage devices formed from a combination of lithium-ion battery electrode materials with those of supercapacitors. They exhibit better electrochemical properties in terms of energy and power densities than the above mentioned storage systems. In this work, lithium manganese oxide spinel (LiMn2O4; LMO) and lithium manganese phosphate (LiMnPO4; LMP) as well as their respective nickel-doped graphenised derivatives (G-LMNO and G-LMNP) were synthesized and each cathode material used to fabricate lithium ion capacitors in an electrochemical assembly that utilised activated carbon (AC) as the negative electrode and lithium sulphate electrolyte in a two-electrode system. The synthetic protocol for the preparation of the materials followed a simple solvothermal route with subsequent calcination at 500 - 800 ?C. The morphological, structural and electrochemical properties of the as prepared materials were thoroughly investigated through various characterisation techniques involving High resolution scanning electron microscopy (HRSEM), High resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), Small-angle X-ray scattering (SAXS), Electrochemical impedance spectroscopy (EIS), Cyclic voltammetry (CV) and Galvanostatic charge/discharge.
2021-12-31

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27

Jensen, Zachary R. "Improvements to the Two-Point In Situ Method for Measurement of the Room Constant and Sound Power in Semi-Reverberant Rooms." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/5724.

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The two-point in situ method is a technique for measuring the room constant of a semi-reverberant room and the sound power of a source in that room simultaneously using two measurement positions. Using a reference directivity source, where the directivity factor along any given axis of the source has been measured, one is able to use the Hopkins-Stryker equation to measure both the room constant and the sound power level of another source rather simply. Using both numerical and experimental data, it was found that by using generalized energy density (GED) as a measurement quantity, the results were more accurate than those using squared pressure. The results also improved when one measurement position was near the source and the other measurement position was far from the source. This resulted in strong contribution of both the direct and reverberant fields in each of the measurement positions. Another improvement to the two-point method was the use of a local, spatial average around the measurement position. The assumptions in the Hopkins-Stryker equation rely on this average and it was found that a small local spatial average improved the measurements. However, this improvement was greater for squared pressure than for GED. Several source sound power levels and room constants were measured to show that these measurements are improved by using the suggested techniques.

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28

PEREIRA, SERGIO A. "Conceito alternativo de um reator hibrido (conjunto sub-critico acoplado com acelerador)." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10991.

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Made available in DSpace on 2014-10-09T12:46:36Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T13:56:41Z (GMT). No. of bitstreams: 1 08350.pdf: 7511291 bytes, checksum: 18b3142f54961c0556b2d92490449a3a (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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29

Ji, Xiaoyan. "Thermodynamic properties of humid air and their application in advanced power generation cycles." Doctoral thesis, Stockholm : Department of Chemical and Engineering and Technology, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4129.

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30

Youard, Timothy John. "Feasibility of an Electric Jetpack." Thesis, University of Canterbury. Electrical and Computer Engineering, 2010. http://hdl.handle.net/10092/5293.

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The Martin Aircraft Company Limited has been developing the Martin Jetpack for over 25 years. The recent worldwide launch of the Jetpack has enabled the company to step up its research and development programme. The goal of this project was to determine the feasibility of an electrically powered version of the Martin Jetpack. The feasibility of the Electric Jetpack was determined by researching energy storage technologies, researching power cable technologies, simulations of flight times, surveys of electric motors, and the development of a simulation program which was used to optimise some preliminary custom motor designs. The overall conclusion of this project was that the Electric Jetpack was feasible only when it was powered through a tethered power cable, and on-board energy storage was not used. An investigation into current energy storage technologies showed that the Electric Jetpack is not considered feasible when using on-board energy storage, however it is possible to obtain flight for a very short time. The energy storage technologies studied were batteries, fuel cells, and ultra-capacitors. It was found that the best performing technology was the lithium iron nano-phosphate battery. A simulation of flight time showed that this battery type would be able to provide flight for approximately 3.6 minutes. Future trends indicated that the Electric Jetpack with on-board energy storage may eventually be feasible when using a lithium-ion based battery due to improvements being made in energy density and power density. By using a tethered power cable, the weight of the on-board energy storage could be eliminated. This was shown to be a feasible method for powering the Electric Jetpack for applications where the Jetpack needs to only be operated in a small area. The best cable type to use was a multi-stranded flexible cable operating at a high DC bus voltage. The weight of a 5 meter power cable using a 1000 V bus voltage was shown to be 4.9 kg. Potential applications for this kind of Jetpack could include thrill rides and rescue operations from multi-storied buildings. A cable made from carbon nanotubes was shown to be a future technology that could offer a lighter cable. A survey of currently available electric motors showed that none met both the power density and speed required by the Electric Jetpack, even when using a tethered power cable to eliminate the energy storage weight. Because of this, a custom motor design was needed. Research into motor technologies showed that the permanent magnet brushless DC (PMBLDC) motor was the most suited type for the Electric Jetpack. The permanent magnet brushless AC (PMBLAC) motor was also suitable. A PMBLDC motor simulation program was developed using MATLAB which could be used to optimise preliminary custom designs. A characterisation of allowable motor time constants for the PMBLDC motor type was made in order to speed up the simulation time. The optimisation results showed that a power density of 5.41 kW/kg was achievable for the motor when it was located inside the ducted fan tubes, and a power density of 6.56 kW/kg was achievable when the motor was located outside the ducted fans and operated at a higher speed. The motor designs were shown to be within the expected torque per unit rotor volume (TRV) range for aerospace machines. The best power density figures would leave between 37 kg and 42 kg of weight for the motor driver/controller, cable weight, and miscellaneous motor parts. This was considered to be feasible. An FEM simulation was made on one of the optimised motor designs. The FEM results agreed with the parametric results within reasonable accuracy. The parametric back-EMF waveform over-estimated the effects of slotting.

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31

RAFIQUE, AMJID. "Flexible Fiber-Shaped Supercapacitor for Wearable Electronics." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2729354.

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32

Metchueng, Kamdem Syntia. "Stockage de chaleur dans l'habitat par sorption zéolite/H2O." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI059/document.

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Le couple zéolite/H2O, qui présente une densité énergétique importante et remplit les conditions d’innocuité requises pour un système de stockage de chaleur pour l’habitat, est mis en œuvre dans réacteur modulaire à lit fixe. Un modèle monodimensionnel de transferts couplés de masse et de chaleur dans un lit fixe de grains de zéolite parcourus par un flux d'air humide été élaboré. Ce dernier a été conçu de façon à pouvoir intégrer rapidement des données sur de nouvelles générations de matériaux et coupler le réacteur à d’autres modèles : bâtiment/sous-station/quartier. L'étape de validation expérimentale montre que le modèle permet une estimation satisfaisante de l'autonomie, la durée d'amorçage et la puissance moyenne fournie en phase de décharge ainsi que la durée de charge. Ce modèle est donc un bon outil de dimensionnement et de pilotage du réacteur. L'analyse de sensibilité a montré que l'amélioration des prévisions du modèle requiert une évaluation plus précise de la chaleur complémentaire de sorption et de la porosité du lit. Après avoir estimé les besoins de chauffage d'une maison BBC deux dimensionnements ont été proposés afin d'effacer soit l'hyper-pointe de 18h - 20h soit la semaine la plus froide. Si la première stratégie aboutit à un système de stockage plus compact, la seconde permet de réduire le nombre de cycles marche/arrêt. Pour un îlot de 50 maisons BBC, la notion de foisonnement est considérée lors de l'estimation des besoins en chauffage pendant la semaine la plus froide. La phase de charge du système de stockage se ferait par le biais de la chaleur fatale récupérée dans l'industrie. Pour des stratégies d'effacement similaires (semaine la plus froide en hiver), un volume équivalent de 544 litres par maison dans l'îlot suffit pour répondre aux besoins de chauffage à Nancy contre 580 litres pour une maison BBC seule
Heat storage systems for residential house heating could contribute to smoothing the load curve and would help prevent the use of the most polluting power plants or electricity imports during consumption peaks. Thermochemical heat storage systems are suitable for the intended application since they have high energy densities and low thermal losses. This thesis focuses on the design of an adsorption heat storage system that would be used to shed the load curve of the heating device of a house or residential district during the winter peak consumption periods. The zeolite/H2O pair, which has interesting features such as a high energy density and meets the conditions of safety required for a heat storage system for housing, is implemented in a modular fixed bed reactor. A 1D pseudo-homogeneous model was developed in order to simulate the performance of a fixed bed of zeolite during the adsorption and desorption of water. The latter was designed so as to facilitate the integration of data on new generations of materials and model couplings. The need to obtain data on the sorption properties of the zeolite/H2O pair to have reliable simulation results has been demonstrated, particularly at low partial pressures of water vapor and under the operating conditions selected. The experimental validation phase shows that the pseudo-homogeneous model provides a satisfactory estimate of criteria such as the autonomy, the responsiveness and the average power delivered during the discharging phase and the charging time. The model is thus a good sizing and management tool of the reactor. A sensitivity analysis, with the method of Morris, showed that improved model estimates require a more accurate assessment of the additional heat of sorption and porosity of the bed. After assessing the heating needs of the LEB house with a thermal model of the latter in cold climate conditions, two heat storage reactors were sized in order to shed the heating system's load curve either between 6 and 8pm or during the coldest week of the year. While the first strategy results in a more compact storage system, the second makes it possible to reduce the number of on/off cycles. The need for predictive control for monitoring the storage system was highlighted. As for the residential district of 50 LEB houses, diversity is considered when estimating the heating needs of the latter during the coldest week in Nancy. The heat source during the charging phase of the container would be industrial waste heat. During the coldest week, two sizings are suggested. For similar load shedding strategies, the comparison of the equivalent storage volume per house in the district with the storage volume for a single house serves highlights the importance of taking into account diversity. In order to meet the heating needs in Nancy, an equivalent volume of 544 liters per house in the district is sufficient whereas 580 liters are needed for a LEB house

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33

Chester, Ryan T. "Error Sensor Strategies for Active Noise Control and Active Acoustic Equalization in a Free Field." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2298.pdf.

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34

Ayme, Fabien. "Développement d'une méthode énergétique pour l'évaluation expérimentale des flux acoustiques entrants dans les cavités d'avion." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00995861.

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La hiérarchisation de la puissance injectée par des sources acoustiques dans une cavité d'avion telle qu'un cockpit, en vol, revêt un caractère majeur dans le but d'en réduire le bruit intérieur. Afin de répondre à ce besoin, la nécessité de considérer la cavité dans son ensemble à l'aide d'une méthode globale se révèle importante. Au cours de cette thèse, une méthode d'identification basée sur une méthode énergétique locale, appelée MES pour Méthode Energétique Simplifiée, est utilisée. En connaissant la géométrie de la cavité, ainsi que l'absorption des matériaux qui la composent, elle permet de déterminer la puissance rayonnée par les différentes sources acoustiques à l'intérieur de la cavité, à l'aide de mesures d'intensité tridimensionnelle, et de densité d'énergie acoustique totale. Afin de tester la méthode dans un cas réel, mesurer ces quantités énergétiques s'avère alors nécessaire. Une sonde acoustique est donc conçue, fabriquée, testée et enfin validée. Basée sur quatre mesures de pressions réalisées autour d'une sphère rigide à l'aide de microphones électrostatiques déportés, elle permet de mesurer la pression et le vecteur vitesse particulaire au centre de la sphère, et d'en déduire alors l'intensité 3D et la densité d'énergie totale. Un démonstrateur est ensuite construit pour réaliser des essais. Il s'agit d'une maquette de cockpit basée sur celui de l'A380. Différents essais acoustiques et vibro-acoustiques permettent alors de démontrer la capacité de l'association formée par la méthode d'identification et la sonde à déterminer la puissance injectée par les différentes sources dans des conditions acoustiques plus ou moins sévères, avec une précision de l'ordre de 2dB. Le post-traitement à l'aide de la MES des flux acoustiques rayonnés ainsi déterminés permet également de reconstruire le champ acoustique dans la cavité, ainsi que de séparer les différentes contributions en des points d'intérêt tels que les têtes pilote et copilote.

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35

Novell, Sara T. "Design of Structural Stand for High-Precision Optics Microscopy." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2132.

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Lawrence Livermore National Lab (LLNL) is home to the National Ignition Facility (NIF), the world’s largest and most energetic laser. Each of the 192 beamlines contains dozens of large optics, which require offline damage inspection using large, raster-scanning microscopes. The primary microscope used to measure and characterize the optical damage sites has a precision level of 1 µm. Mounted in a class 100 clean room with a raised tile floor, the microscope is supported by a steel stand that structurally connects the microscope to the concrete ground. Due to ambient vibrations experienced in the system, the microscope is only able to reliably reach a 10-µm level of precision. As NIF’s technology advances, there is a need to both increase optic measurement throughput and to measure damage sites at a higher level of precision. As a result, there is to be another microscope mounted into another clean room lab at LLNL. To assure the microscope can meet its specified level of precision, the stand on which it is mounted was designed to meet the rigorous Environmental Vibrational Criteria standards, or VC curves. Through the collection of random vibrational data using accelerometers and Power Spectral Density (PSD) analysis, the stand was designed to meet the VC-C curve requirement of velocities below 12.5 µm/sec. Furthermore, the stand design was optimized to avoid resonance at common vibrational signatures throughout the frequency spectrum, placing its first natural frequency at a sufficiently high level to minimize amplification.

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36

Toni, Kotchikpa Arnaud. "Conception et intégration d'un convertisseur buck en technologie 28 nm CMOS orientée plateformes mobiles." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI049.

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Ce travail de thèse présente la conception d’un convertisseur Buck 3 états pour améliorer le comportement dynamique des tensions d’alimentations des microprocesseurs. La topologie du convertisseur est dans un premier temps, implémentée en technologie IBM CMOS 180 nm pour la validation de la structure 3 états. Le prototype réalisé utilise une tension d’entrée de 3.6V et génère une tension de sortie de 0.8V à 2V. Sa réponse aux transitoires de charge ne montre que 1 à 2% de surtension prouvant ainsi l’avantage du régulateur en dynamique. Le convertisseur 3 états est dans un deuxième temps intégré en technologie 28 nm CMOS HPM (cette technologie est essentiellement utilisée pour les microprocesseurs). Les résultats des tests effectués sur le prototype réalisé confirment les performances en économie d’énergie, de surface et de réponse dynamique. Ce prototype délivre en effet 0.5 à 1.2V en sortie pour 1.8V en entrée et présente un rendement maximal de 90%. Les mesures de régulation dynamique montrent qu’il permet d’obtenir moins de 5% de bruit sur le processeur et 10 mV/ns de commutation de tensio
This thesis work consists into the design of a 3 states buck converter targeting the improvement of dynamic regulation of microprocessors supplies. The topology of the converter is, at first, implemented in IBMCMOS 180 nm technology to validate the transient performances of the3 states regulator. The prototype in 180 nm, uses an input voltage of 3.6V and outputs a voltage in the range of 0.8V to 2V. Its response to load transients shows about 1% of undershoot and 2 % of overshoot, proving a good dynamic behavior for a simple structure compared to state of the art.The 3 states converter is then integrated in 28 nm CMOS HPM (technologymostly used for microprocessors desgn). The experimental results on the prototype confirm the performances in terms of energy and area savings, aswell as dynamic response. The chip delivers 0.5V to 1.2V from a 1.8V supply,and shows a 90% peak efficiency. The measurements of dynamic regulation show less than 5% of noise on the processor supply and 10 mV/ns outputvoltage switching for DVFS purpose

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37

Kirichenko, E., and E. Belovol. "High-energy-density sugar biobattery." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/45213.

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The rapidly growing demand for powering portable electronic devices is driving the development of better batteries with features such as enhanced energy-storage densities, high levels of safety, biodegradability and small environmental footprints. The lithium-ion battery is often the system of choice because it offers a high energy density, has a flexible and light-weight design and has a longer lifespan than comparable battery technologies. The widespread use of metal-catalysed batteries also raises many concerns, primarily related to safety, toxic metal pollution and the availability of costly, limited, irreplaceable or rare metal resources.

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38

Bouchaala, Dhouha. "Investigation of Current Excitation for Personal Health and Biological Tissues Monitoring." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-204801.

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Bioimpedance spectroscopy is very useful in biomedical field as a safe and non-invasive technique. A stable and safe excitation current below than 0.5 mA for load impedances changing from 100 Ω to 10 kΩ in the full β-dispersion range from kHz up to 1 MHz is a big challenge for the design of the current source addressed by this thesis. For a good stability and high accuracy, the source should have a high output impedance. Different current source types in “current-mode approach” and “voltage-mode approach” were investigated and compared for usability in bioimpedance measurement systems. The “voltage-mode approach” with grounded load was proven to be more suitable and stable for biomedical measurements. Thereby the Tietze and the Howland circuit in dual configuration with negative feedback have shown the lowest error of the output current and the highest output impedance, where the improved Howland circuit in dual configuration with negative feedback is preferred because it has a simple structure, high accuracy and good stability. We suggest to improve the stability of the Howland circuit in dual configuration with negative feedback by introducing compensated operational amplifiers and to reduce stray capacitances at higher frequencies by adding gain compensation capacitor. We reach thereby an accuracy of 0.5% at low frequency and 0.9% at 1 MHz. With the realized accuracy of the designed voltage controlled current source, one decisive prerequisite for portable bioimpedance measurement system is achieved. In order to select the appropriate excitation signals for short measurement time, a comparative study of signals and their parameters was carried out. It leads to the selection of binary chirp signal as a suitable excitation signal due to its short measurement time about 100 μs, low crest factor lower than 2.8 and an energy efficiency higher than 54% in a very noisy signal. Simulation results show that the designed enhanced Howland current source excited by the binary chirp signal has low error and flatness in the whole range
Die Bioimpedanzspektroskopie gewinnt aufgrund ihrer besonderen Eigenschaften als nicht-invasive, schonende Messmethode zunehmend an Bedeutung im biomedizinischen Bereich. Dabei ergeben sich besondere erausforderungen für den Entwurf der Stromquelle zur Realisierung eines stabilen und sicheren Anregungsstroms. Gefordert ist eine hohe Genauigkeit bis zu einem Maximalstrom von 0.5 mA in einem Frequenzbereich, der der β-Dispersion entspricht, von wenigen kHz bis hin zu 1 MHz. Die Stabilität muss bei variablen Lastimpedanzen im Bereich von 100 Ω bis 10 kΩ gewährleistet sein. Dafür muss die Stromquelle eine hohe Ausgangsimpedanz aufweisen. Diese Arbeit fokussiert auf den Entwurf von spannungsgesteuerten Stromquellen. Verschiedene Arten von Stromquellen wurden untersucht und verglichen. Der "Voltage-Modus-Ansatz" mit Masse-referenzierter Last hat sich als besser geeignet und stabiler für biomedizinische Messungen erwiesen. Die Tietze-Schaltung und diese Howland-Schaltung zeigen dabei die niedrigsten Fehler des Ausgangsstroms und die höchste Ausgangsimpedanz. Im direkten Vergleich besitzt die verbesserte Howland-Schaltung doch eine einfachere Struktur, höhere Genauigkeit und bessere Stabilität und wird daher gegenüber der Tietze-Schaltung bevorzugt. Um weitere Stabilitätsverbesserungen bei der Howland-Schaltung zu erreichen, werden zwei Maβnahmen vorgeschlagen. Zum einen werden kompensierte Operationsverstärker eingeführt und zum anderen wird der Einfluss von Streukapazitäten bei hohen Frequenzen minimiert indem die Verstärkung mit Kondensatoren kompensiert wird. Durch diese Maβnahmen wird eine Genauigkeit von 0.5% bei niedrigen Frequenzen und 0.9% bei 1 MHz ermöglicht. Mit dem neuen Entwurf der spannungsgesteuerten Stromquelle ist ein entscheidender Meilenstein für die Realisierung tragbarer Messsysteme der Bioimpedanz erreicht. Um eine kurze Messzeit zu realisieren wurde eine vergleichende Studie von Anregungssignalen und deren Signalparameter durchgeführt. Die Ergebnisse zeigen, dass binäre Chirp-Signale aufgrund der reduzierten Messzeit, des niedrigen Crest-Faktors unter 2.8 und hohe Energieeffizienz von mehr als 54% bei hohem Rauschlevel besonders geeignet sind. Simulationsergebnisse zeigen, dass die entwickelte Howland-Stromquelle zusammen mit einem binären Mehrfrequenzsignal den geringsten Amplitudenfehler im gesamten Frequenzbereich realisiert

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39

Erices, Muñoz Eduardo Andrés, and Rojas Cristian Patricio Torres. "Sun Power Energy." Tesis, Universidad de Chile, 2015. http://repositorio.uchile.cl/handle/2250/137206.

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Tesis para optar al grado de Magíster en Administración
Eduardo Andres Erices Muñoz [Parte I Análisis estratégico y de mercado], Cristian Patricio Torres Rojas [Parte II Análisis organizativo-financiero]
Autores no autorizan el acceso a texto completo de su documento
La necesidad de aumentar la capacidad instalada de la matriz energética del país es un tema que en la última década se ha instalado en la agenda nacional, dado que el crecimiento económico de Chile implica un mayor consumo eléctrico. A su vez, la estrechez energética se ve representada con mayor profundidad en la industria de la minería, especialmente en el norte grande de Chile. El sector minero, además de ser el principal consumidor de energía eléctrica del país, ha experimentado desde el año 2000 una caída sostenida en su productividad, entre otros factores, por los mayores consumos y costos de la energía eléctrica, enfrentando actualmente uno de los precios más altos de América Latina1. Dado lo anterior, el Gobierno está asumiendo un rol más activo, definiendo una Agenda de Energía que incluye como uno de sus ejes el compromiso que un 45% de la capacidad eléctrica que se instalará en el país hasta el año 2025 sean energías renovables no convencionales (ERNC) y, de esta forma, cumplir con la meta de la Ley 20/25 de ingresar a la matriz energética un 20% de ERNC para dicho año. En este sentido, la energía fotovoltaica es una alternativa técnicamente viable para cubrir el consumo eléctrico, principalmente en el norte grande del país, dado que posee un importantísimo potencial solar. El propósito del presente plan de negocios es evaluar la factibilidad económica y financiera de ingresar al negocio de las energías renovables no convencionales, de una manera no convencional. Más allá de este juego de palabras, dado que la mayoría de los proyectos de generación de energía limpia se basan en el modelo de negocios tradicional, o sea generando e inyectando energía al sistema y transando los precios en el mercado spot, la oportunidad de negocio se visualiza en vender directamente la energía a la industria minera, sin intermediarios ni costos de transmisión relevantes. La industria eléctrica nacional está dividida en tres segmentos: generación, transmisión y distribución de energía eléctrica. Las actividades de transmisión y distribución tienen el carácter de monopolio natural. El sector de generación opera en condiciones de competencia, no obstante se caracteriza por ser un mercado altamente concentrado. Asimismo, existen cuatro sistemas eléctricos siendo los dos más importantes el SING (Sistema Interconectado del Norte Grande) y el SIC (Sistema Interconectado Central). La matriz energética del SING se alimenta en un 95% de fuentes térmicas (carbón, diésel, gas natural). En cuanto al desarrollo de proyectos ERNC, a pesar que el país posee condiciones naturales favorables para las energías solar y eólica, recién en el año 2014 se observó un “despegue” de las ERNC en Chile, materializándose proyectos con una capacidad instalada de casi 1.000 MW. Además, a nivel mundial la curva de aprendizaje en el costo de fabricación y operación de la tecnología solar fotovoltaica, ha permitido alcanzar precios competitivos respecto a las fuentes convencionales de energía. El mercado objetivo se concentra en el segmento de generación, a través del suministro eléctrico en base a energías renovables no convencionales, específicamente solar tipo fotovoltaica, para las empresas mineras (cobre) ubicadas en las regiones de Tarapacá y Antofagasta, ya que reúnen las condiciones de vida útil de la faena minera y disponibilidad de terrenos, de acuerdo a la propuesta de valor del proyecto. El modelo de negocios consiste en satisfacer parte de la demanda de energía eléctrica de las empresas mineras señaladas en el párrafo anterior, por medio de una planta solar fotovoltaica de 3 MW de potencia instalada y a través de un contrato de suministro tipo PPA (Power Purchase Agreement) a 20 años. La ventaja competitiva consiste en ofrecer una tarifa estable durante el período del contrato más baja que su tarifa actual en base a generación convencional, lo cual permitirá al cliente capturar y proyectar el ahorro en sus costos operativos. Además, la propuesta tiene la característica que la planta se construirá in-situ, aprovechando la superficie disponible en la faena minera, generando valor compartido en la economía de escala por el costo del terreno y línea de transmisión y conexión eléctrica. La operación y mantenimiento de la planta fotovoltaica estará a cargo de nuestra empresa. Para el desarrollo del negocio, dado que implica montos de inversión relevantes (USD 5,6 millones para cada planta) y se requiere de un respaldo tecnológico y logístico para realizar ese tipo de proyectos, se creará una Unidad Estratégica de Negocio (UEN) denominada “SUN POWER ENERGY” (SPE), bajo la estructura organizacional de E.CL S.A., una de las empresas principales que operan en el SING. Finalmente, en la evaluación financiera se contempla la ejecución de tres plantas solares dentro de los primeros seis años, con un total de aporte de capital requerido de USD 10 millones. Se ha considerado el apalancamiento financiero del proyecto, mediante la obtención de préstamos bancarios por USD 7,8 millones. Como resultado, través del valor actual de los flujos de caja libres descontados a una tasa del 7,5%, se obtiene un valor de la empresa sin deuda de USD 52.382, con una TIR del 7,5% y un periodo de recuperación de la inversión (payback) de 12 años. La TIR del inversionista alcanza al 7,9% con un VAN ajustado de USD 576.161.

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40

Kim, Hyea. "High energy density direct methanol fuel cells." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37106.

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The goal of this dissertation was to create a new class of DMFC targeted at high energy density and low loss for small electronic devices. In order for the DMFC to efficiently use all its fuel, with a minimum of balance of plant, a low-loss proton exchange membrane was required. Moderate conductivity and ultra low methanol permeability were needed. Fuel loss is the dominant loss mechanism for low power systems. By replacing the polymer membrane with an inorganic glass membrane, the methanol permeability was reduced, leading to low fuel loss. In order to achieve steady state performance, a compliant, chemically stable electrode structure was investigated. An anode electrode structure to minimize the fuel loss was studied, so as to further increase the fuel cell efficiency. Inorganic proton conducting membranes and electrodes have been made through a sol-gel process. To achieve higher voltage and power, multiple fuel cells can be connected in series in a stack. For the limited volume allowed for the small electronic devices, a noble, compact DMFC stack was designed. Using an ADMFC with a traditional DMFC including PEM, twice higher voltage was achieved by sharing one methanol fuel tank. Since the current ADMFC technology is not as mature as the traditional DMFCs with PEM, the improvement was accomplished to achieve higher performance from ADMFC. The ultimate goal of this study was to develop a DMFC system with high energy density, high energy efficiency, longer-life and lower-cost for low power systems.

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41

Khorashad, Arash Sorouri. "Investigation of the exchange energy density functional." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504765.

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Density Functional Theory (DFT) is an important tool in the treatment of quantum many-body problems. In spite of being exact in principle, the application of DFT requires the use of approximations, because it involves an unknown universal functional called the exchange-correlation energy. In this thesis we describe an accurate and efficient extension of Chawla and Voth's planewave based algorithm for calculating exchange energies, exchange energy densities, and exchange energy gradients with respect to wave function parameters in systems of electrons subject to periodic boundary conditions. The theory and numerical results show that the computational effort scales almost linearly with the number of plane waves and quadratically with the number of k vectors. To obtain high accuracy with relatively few k vectors, we use an adaptation of Gygi and Baldereschi's method for reducing Brillouin zone integration errors. We then generate a large database of highly accurate exchange energy densities in 106 artificial but realistic solid-state systems. We use the database not only to examine the accuracy of some important existing exchange functionals, but also to show that there exists a smooth function of the local electron density, its gradient and Laplacian that fits our data well. We also study the effects of twist-averaging on the finite-size errors in the exchange energy of a uniform electron gas, using the Ewald, model periodic Coulomb (MPC) and screened Coulomb interactions. In the case of the Ewald interaction, this investigation is carried out in both the canonical (fixed particle number) and grand-canonical (fixed Fermi wave vector) ensembles. Finally, we study the new reciprocal-space approach to the . Coulomb finite-size errors introduced by Chiesa et al. and find that it is almost equivalent to the use of the MPC interaction.

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Olsson, Robbie Stefan Ian. "High energy density physics in cluster media." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18394.

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Gases comprised of atomic clusters have in the past been shown to exhibit extremely strong absorption of high-intensity laser pulses. By using this target medium, it is possible to use laser systems with only modest energies to create High Energy Density Plasmas. Not only are the plasmas created in this way of interest in themselves, but when properly designed, these experiments can be used as a platform for Laboratory Astrophysics studies of radiative blast waves. This thesis describes experiments which investigate the evolution of radiative blast waves, the interaction of relativistic laser pulses with large atomic clusters and the nature of the post laser-cluster interaction upstream medium into which the shock propagates. Experiments were carried out to diagnose the properties of the upstream medium into which radiative shocks launched by the laser-cluster interaction propagate. This experiment was conducted using the Blackett Laboratory Laser Consortium Nd:Glass laser system with a novel perpendicular heating beam geometry. By introducing a time delay between the perpendicular beams, it was possible to track the propagation of a ballistic cluster disassemble wave. This wave was shown to be the product of ~200 keV ions ejected by the initial laser cluster-interaction. Also discussed in this thesis are the results of the first laser-cluster experiment to be conducted on the Central Laser Facility's Astra-Gemini system. Here the interaction of large atomic clusters with relativistic laser pulses is investigated. X-Ray pinhole camera images have been captured of the early time plasma created by the laser-clusters interaction. For the first time the absorption properties of large atomic clusters irradiated by a femtosecond high energy, ~14 J, laser pulse have been studied. Furthermore, the temporal evolution of radiative blast waves launched from the laser-cluster interaction is described. In the past the Vulcan laser system at RAL was used to launch blast waves which displayed velocity domain oscillations driven by the radiation emitted by the blast wave. This instability has again been observed in the work reported here and the threshold for onset has been investigated.

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43

Xu, Buye. "Generalized Acoustic Energy Density and Its Applications." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2339.

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The properties of acoustic kinetic energy density and total energy density of sound fields in lightly damped enclosures have been explored thoroughly in the literature. Their increased spatial uniformity makes them more favorable measurement quantities for various applications than acoustic potential energy density (or squared pressure), which is most often used. In this dissertation, a new acoustic energy quantity, the generalized acoustic energy density (GED), will be introduced. It is defined by introducing weighting factors, α and 1 − α, in the formulation of total acoustic energy density. With the additional degree of freedom, the GED can conform to the traditional acoustic energy density quantities, or be optimized for different applications. The properties and applications of the GED are explored in this dissertation. For enclosed sound fields, it was found that GED with α = 1/4 is spatially more uniform than the acoustic potential energy density, acoustic kinetic energy density, and the total acoustic energy density, which makes it a more favorable measurement quantity than those traditional acoustic energy density quantities for many indoor measurement applications. For some other applications, such as active noise control in diffuse field, different values of α may be considered superior. The numerical verifications in this research are mainly based on a hybrid modal expansion developed for this work, which combines the free field Green's function and a modal expansion. The enclosed sound field is separated into the direct field and reverberant field, which have been treated together in traditional modal analysis. Studies on a point source in rectangular enclosures show that the hybrid modal expansion converges notably faster than the traditional modal expansions, especially in the region near the source, and introduces much smaller errors with a limited number of modes. The hybrid modal expansion can be easily applied to complex sound sources if the free field responses of the sources are known. Damped boundaries are also considered in this dissertation, and a set of modified modal functions is introduced, which is shown to be suitable for many damped boundary conditions.

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44

Shin, Il-Won. "POWER SPECTRAL DENSITY ANALYSIS OF PRINTER DEFECT." UKnowledge, 2005. http://uknowledge.uky.edu/gradschool_theses/266.

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A potential characterization tool for printer quality is the power spectral density (PSD) analysis of flat-field printer outputs. This thesis explains the relationship between the PSD and characteristics of printer defects using examples of scanned printer outputs. In addition, a protocol is also presented for scanning flat fields and performing a PSD analysis. The protocol considers sampling and windowing issues to best focus on defects or quality issues of interest. The main objective of this work is to determine the interactive relationships of print defect patterns such as graininess, streaking, and banding under flat-field hardcopy outputs. The additive and multiplicative models are considered for describing the interaction between printer defects. Simulated print defect patterns and metrics base on the PSD are used to demonstrate the patterns generated by multiplicative and additive processes. These results are compared the PSD of actual flat-field prints from digital printers to draw conclusion concerning actual artifact interaction. For all defects examined the additive model is shown to be a good model of the interactions between printer defects.

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45

Chen, Zheng. "Electrical Integration of SiC Power Devices for High-Power-Density Applications." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23923.

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The trend of electrification in transportation applications has led to the fast development of high-power-density power electronics converters. High-switching-frequency and high-temperature operations are the two key factors towards this target. Both requirements, however, are challenging the fundamental limit of silicon (Si) based devices. The emerging wide-bandgap, silicon carbide (SiC) power devices have become the promising solution to meet these requirements. With these advanced devices, the technology barrier has now moved to the compatible integration technology that can make the best of device capabilities in high-power-density converters. Many challenges are present, and some of the most important issues are explored in this dissertation. First of all, the high-temperature performances of the commercial SiC MOSFET are evaluated extensively up to 200 degree C. The static and switching characterizations show that the device has superior electrical performances under elevated temperatures. Meanwhile, the gate oxide stability of the device - a known issue to SiC MOSFETs in general - is also evaluated through both high-temperature gate biasing and gate switching tests. Device degradations are observed from these tests, and a design trade-off between the performance and reliability of the SiC MOSFET is concluded. To understand the interactions between devices and circuit parasitics, an experimental parametric study is performed to investigate the influences of stray inductances on the MOSFETs switching waveforms. A small-signal model is then developed to explain the parasitic ringing in the frequency domain. From this angle, the ringing mechanism can be understood more easily and deeply. With the use of this model, the effects of DC decoupling capacitors in suppressing the ringing can be further explained in a more straightforward way than the traditional time-domain analysis. A rule of thumb regarding the capacitance selection is also derived. A Power Electronics Building Block (PEBB) module is then developed with discrete SiC MOSFETs. Integrating the power stage together with the peripheral functions such as gate drive and protection, the PEBB concept allows the converter to be built quickly and reliably by simply connecting several PEBB modules. The high-speed gate drive and power stage layout designs are presented to enable fast and safe switching of the SiC MOSFET. Based on the PEBB platform, the state-of-the-art Si and SiC power MOSFETs are also compared in the device characteristics, temperature influences, and loss distributions in a high-frequency converter, so that special design considerations can be concluded for the SiC MOSFET. Towards high-temperature, high-frequency and high-power operations, integrated wire-bond phase-leg modules are also developed with SiC MOSFET bare dice. High-temperature packaging materials are carefully selected based on an extensive literature survey. The design considerations of improved substrate layout, laminated bus bars, and embedded decoupling capacitors are all discussed in detail, and are verified through a modeling and simulation approach in the design stage. The 200 degree C, 100 kHz continuous operation is demonstrated on the fabricated module. Through the comparison with a commercial SiC phase-leg module designed in the traditional way, it is also shown that the design considerations proposed in this work allow the SiC devices in the wire-bond structure to be switched twice as fast with only one-third of the parasitic ringing. To further push the performance of SiC power modules, a novel hybrid packaging technology is developed which combines the small parasitics and footprint of a planar module with the easy fabrication of a wire-bond module. The original concept is demonstrated on a high-temperature rectifier module with SiC JFET. A modified structure is then proposed to further improve design flexibility and simplify module fabrication. The SiC MOSFET phase-leg module built in this structure successfully reaches the switching speed limit of the device almost without any parasitic ringing. Finally, a new switching loop snubber circuit is proposed to damp the parasitic ringing through magnetic coupling without affecting either conduction or switching losses of the device. The concept is analyzed theoretically and verified experimentally. The initial integration of such a circuit into the power module is presented, and possible improvements are proposed.
Ph. D.

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46

Nikonov, M. "Energy resources: wave power." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/62834.

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The topic of renewable energy is an evergreen subject, especially, in a world dominated by fossil fuels. Renewable energy is widely discussed in the contemporary world because it is unlimited, which means it’s sustainable and does not emit greenhouse gasses that are harmful to the environment and human life. A classic example of renewable energy is wave energy.

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馮錦生 and Kam-sang Fung. "Fatigue crack propagation with strain energy density approach." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31209713.

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48

Chung, Kang Ko. "Heteroatom-containing carbons for high energy density supercapacitor." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/6982/.

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The supercapacitor is one of the most important energy storage devices as its construction allows for addressing many of the drawbacks related to batteries, but the low energy density of current systems is a major issue. In this doctoral dissertation, with a view to attaining high energy density supercapacitor systems that can be comparable to those for batteries, new heteroatom-containing carbons in the form of particles and three-dimensional films were investigated. A nitrogen-containing material, acrodam, was chosen as the carbon precursor due to the inexpensiveness, high carbonization yield, oligomerizability, etc. The carbon particles were prepared from acrodam together with caesium acetate as a meltable flux agent, and disclosed excellent properties in hydroquinone-loaded sulphuric acid electrolyte with high energy densities (up to 133.0 Wh kg–1) and sufficient cycle stabilities. These properties are already now comparable to those of batteries. Besides, conductive carbon three-dimensional films were fabricated using acrodam oligomer as the precursor by the inexpensive spin coating method. The films were found to be homogeneous, flat, void- and crack-free, and high conductivities (up to 334 S cm–1) could be obtained at the carbonization temperature of 1000 ºC. Furthermore, a porous carbon three-dimensional film could be formed using an organic template at the first attempt. This finding demonstrates the film’s potentiality for various applications such as supercapacitor electrode; the essential absence of contact resistance within the network should contribute to effective transportation of electron within the electrode. The progress made in this dissertation will open a new way to further enhancement of energy density for supercapacitor as well as other applications that exceeds the current properties.
Der Superkondensator ist einer der wichtigsten Energiespeicher da seine Konstruktion die Lösung vieler Nachteile von Batterien erlaubt. Allerdings weisen derzeitige Systeme noch zu geringe Energiedichten auf. Um Superkondensatoren mit Energiedichten vergleichbar zu Batterien zu ermöglichen, wurden in der vorliegenden Dissertation neue, heteroatomhaltige Kohlenstoffe in Form von Partikeln und Filmen untersucht. Aufgrund geringer Kosten, hohen Ausbeuten, Polymerisierbarkeit usw. wurde die stickstoffhaltige Substanz Acrodam als Kohlenstoffvorstufe verwendet. Die Kohlenstoffpartikel wurden ausgehend von Acrodam zusammen mit Cäsiumacetat als schmelzbares Flussmittel hergestellt und wiesen ausgezeichnete Eigenschaften in Hydrochinon geladenen Schwefelsäure-Elektrolyten mit hohen Energiedichten (bis zu 133,0 Wh kg–1) und guten Zyklusstabilitäten auf. Diese Eigenschaften sind bereits jetzt vergleichbar mit denen von Batterien. Weiterhin wurden unter Verwendung von Acrodamoligomeren als Vorstufe und mit Hilfe der kostengünstigen Rotationsbeschichtung leitfähige, dreidimensionale Kohlenstofffilme hergestellt. Bei einer Karbonisierungstemperatur von 1000 °C konnten die Materialien als homogene, flache, Hohlraum-und Riss-freie Filme erhalten werden, die eine hohe Leitfähigkeit (bis zu 334 S cm–1) aufwiesen. Darüber hinaus konnte mit einem organischen Templat ein dreidimensionaler, poröser Kohlenstoff geformt werden. Dies zeigt das Potential der Filme für verschiedene Anwendungen wie Superkondensatorelektroden; die Abwesenheit von Übergangswiderständen im Netzwerk sollte zu einem effizienten Transport von Elektronen in der Elektrode beitragen. Die Ergebnisse dieser Dissertation werden neue Wege zur Verbesserung der Energiedichte von Superkondensatoren sowie weiteren Anwendungen eröffnen.

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Guillaud, Mathilde. "Neutrino oscillations at very high energy/matter density." Thesis, KTH, Fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292510.

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Neutrino oscillations in matter can be studied in different regimes, depending on the energy of the incoming neutrinos and the matter density of the medium. In this thesis we investigate neutrino oscillations in dense matter at very high energy (TeV-PeV range), taking into account the absorption that the neutrinos may undergo in such dense media. This absorption phenomenon is relevant for neutrino telescope measurements of astrophysical neutrinos. We begin with a brief reminder on neutrino oscillations in vacuum and the construction of the PMNS matrix. Then, we proceed with calculations for dense matter. We then explore the accuracy of the resulting effective 2-neutrino mixing formulas. They present a good accuracy for Earth-like densities in our range of energies. We develop the calculations for oscillation probabilities in dense matter with absorption through charged-current inelastic scattering for both the two-neutrino and three-neutrino case. We find that in dense media, astrophysical neutrinos indeed undergoabsorption, which reduces signicantly the fluxes for each flavor, with a resonant absorption of electron-anti-neutrinos around E_{res}\simeq 6.3PeV. We discuss the impact of neutrino absorption in the Earth for neutrino telescopes measurements. We find that solar and lunar shadowing is not problematic for current telescopes but could be a good angular resolution indicator for new telescopes to come.
Neutrinooscillationer i materia kan studeras i olika regimer beroende på inkommande neutrinernas energi och densiteten hos det bakomliggande mediet. I detta examensarbete undersöker vi neutrinooscillationer i gränsen av tät materia och mycket hög energi (TeV-PeV-intervall), och tar hänsyn till den absorption av neutriner som då kan inträffa i sådant materia. Detta absorptionsfenomen är relevant för neutrino-teleskopmätningar av astrofysiska neutriner. Vi börjar med att kort påminna oss om neutrinooscillationer i vakuum och konstruktionen av PMNS-matrisen. Vi försätter sedan med beräkningar av neutrinooscillationer i tät materia. Vi undersöker noggrannheten i resulterande effektiva 2-neutrino-blandningsformlerna. De uppvisar en god noggrannhet i jordlika materieprofiler i vårt intervall av energier. Vi utvecklar beräkningarna av oscillationssannolikheterna i tät materia inklusive absorption genom laddad ström oelastisk spridning i båda två- och tresmaksfallen. Vi finner att astrofysiska neutriner i tät materia absorberas, vilket minskar betydligt flödena för varje smak, med en resonansabsorption av elektron-antineutrino omkring E_res\simeq 6.3PeV. Vi diskuterar sedan effekterna av neutrinoabsorption på jorden för neutrino-teleskopmätningar. Vi finner att sol- och månskuggning är inte problematisk för nuvarande teleskop och kunde vara en bra vinkelupplösningsindikator för kommande teeskop.

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Fung, Kam-sang. "Fatigue crack propagation with strain energy density approach /." [Hong Kong] : University of Hong Kong, 1989. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12827204.

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Дисертації з теми "Energy and power density"

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