Дисертації з теми "Energy tunnel"
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1
Roberts, E. C. "Energy simulation of climatic wind tunnel plant." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/7250.
Повний текст джерелаАнотація:
The Climatic Wind Tunnel (CWT) is a facility used by the motor industry to test vehicles under climatic extremes without the need for expensive overseas test programs. This work focuses on the application of computer simulation to the Heating Ventilation and Air Conditioning (HVAC) plant that makes up a CWT facility. The objective being to reduce its operational costs through the identification of energy saving operational strategies. When in operation the CWT has a peak power consumption of 3MW. The implementation of any measures that would reduce this peak load would give rise to considerable savings in the operating costs of the facility. Computer simulation is an accepted technique for the study of systems operating under varying load conditions. Simulation allows rapid analysis of different strategies for operating plant and the effectiveness of achieving the desired effect without compromising the buildings performance. Models for the components of the CWT have been developed and coded in Neutral Model Format. These models have then been linked together in a modular simulation environment to give a model of the complete plant. The CWT plant naturally decomposesin to four major subsystems these being the test chamber, the soakroom, air make-up and refrigeration system. Models of all the primary and secondary HVAC plant are described as is how they constitute the systems that make up the CWT. Validation tests for individual components as well as for the systems have been carried out. To illustrate the potential of the application of computer simulation into finding improved modes of operation that would reduce the energy consumption of the facility, four studies have been carried out. The studies involve the possibility of scheduling the operation of condenser fans as a function of refrigeration load and outside ambient temperature, methods for the pre-test conditioning of a vehicle, a reduction in the secondary refrigerant flow temperature and an increase in the thickness of the insulated panels from which the facility is constructed. The studies carried out showed that there was potential for moderate energy savings to be made in the operation of the facility and that extended simulation runs would allow for the in-depth assessment of a large range of possible modes of plant operation in order to identify the areas where the greatest savings are possible.
2
Jerjen, Iwan. "Superconducting tunnel junctions as energy resolving single photon detectors /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17113.
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3
Lubitz, William David. "Near real time wind energy forecasting incorporating wind tunnel modeling /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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4
Cavalheiro, David. "Ultra-low power circuits based on tunnel FETs for energy harvesting applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/406391.
Повний текст джерелаАнотація:
There has been a tremendous evolution in integrated circuit technology in the past decades. With the scaling of complementary metal-oxide-semiconductor (CMOS) transistors, faster, less power consuming and more complex chips per unit area have made possible electronic gadgets to evolve to what we see today.
The increasing demand in electronic portability imposes low power consumption as a key metric to analog and digital circuit design. While dynamic power consumption decreases quadratically with the decrease of power supply voltage, leakage power presents a limitation due to the inverse sub-threshold slope (SS). A power supply reduction implies a consequent threshold voltage reduction that, given the fixed SS, cause an exponential increase in leakage current. This poses a limitation in the reduction of power consumption that is inherent to the conventional thermionicbased transistors (MOSFETS and FinFETs). In thermionic-based transistors the SS at room temperature is limited to 60 mV/dec.
To circumvent the SS limitation of conventional transistors, devices with different carrier
injection mechanisms independent of the thermal (Boltzmann) distribution of mobile charge carriers are required. The Tunnel Field-Effect Transistor (TFET) is presented as the most promising post CMOS-technology due to its non-thermal carrier injection mechanism based on Band-To-Band Tunneling (BTBT) effect. TFETs are known as steep slope devices (SS < 60 mV/dec at room temperature). Large current gain (ION/IOFF > 105) at low voltage operation (sub-0.25 V) and extremely low leakage current have already been demonstrated, placing TFETs as serious candidates for ultra-low power and energy efficient circuit applications. TFETs have been explored mostly in digital circuits and applications.
In this thesis, the use of TFETs is explored as an alternative technology also for ultra-low power and voltage conversion and management circuits, suited for weak energy harvesting (EH) sources.
As TFETs are designed as reverse biased p-i-n diodes (different doping types in source/drain regions), the particular electrical characteristics under reverse bias conditions require changes in conventional circuit topologies. Rectifiers, charge pumps and power management circuits (PMC) are designed and analyzed with TFETs, evaluating their performance with the proposal of new topologies that extend the voltage/power range of operation compared to current technologies and circuit topologies. TFET-based PMCs for RF and DC EH sources are proposed and limitations (with solutions) of using TFETs in conventional inductor-based boost converters identified.Ha habido una tremenda evolución en la tecnología de circuitos integrados en las últimas décadas. Con el escalado de transistores de metal-óxido-semiconductor (CMOS), se han hecho posibles chips más rápidos, con menos consumo de energía y más complejos con menos área y esto ha posibilitado la existencia de los aparatos electrónicos que vemos en la actualidad. La creciente demanda de portabilidad implica que el consumo de energía es un indicador clave en el diseño analógico y digital. Mientras que el consumo de potencia dinámica disminuye cuadráticamente con la disminución de la tensión de fuente de alimentación, la potencia de fugas presenta una limitación debido a la pendiente sub-umbral inverso (sub-threshold slope, SS). Una reducción de la tensión de alimentación implica una consecuente reducción de tensión umbral a fin de mantener las prestaciones que, dado el SS fijo, causa un aumento exponencial de la corriente de fuga. Esto plantea una limitación en la reducción de consumo de energía que es inherente a los transistores convencionales basados en inyección de portadores termoiónicos (MOSFETS y FinFETs). En transistores termoiónicos la SS a temperatura ambiente está limitado a 60 mV / dec. Para eludir la limitación SS de transistores convencionales se requieren dispositivos con mecanismos diferentes de inyección de portadores. El transistor túnel de efecto campo (TFET) se presenta como la tecnología más prometedora debido a su mecanismo de inyección de portadores no térmico basado en el efecto Band-To-Band Tunneling (BTBT). Los TFETs se conocen como dispositivos de alta pendiente sub-umbral (SS <60 mV / dec a temperatura ambiente). Han sido ya demostradas ganancias de corriente elevadas (ION / IOFF> 10 ^ 5) en operación de baja tensión (sub-0,25 V) y una corriente de fugas extremadamente bajo, colocando los TFETs como serios candidatos para aplicaciones de circuitos eficientes de ultra-baja potencia y energía. Los TFETs se han explorado sobre todo en circuitos digitales y aplicaciones. En esta tesis, el uso de TFETs se explora como una tecnología alternativa también para circuitos de potencia y de conversión de tensión ultra-bajas, adecuada para fuentes de energía del ambiente, usualmente muy limitadas en magnitud. Debido a que los TFETs están diseñados como diodos p-i-n en polarización inversa (hay diferente tipo de dopaje en las regiones fuente / drenador), sus características eléctricas particulares en condiciones de polarización inversa requieren cambios en las topologías de circuito convencionales. En la tesis, rectificadores, bombas de carga y circuitos de gestión de la energía (PMC) con TFETs se diseñan y analizan, realizando una evaluación de su rendimiento con la propuesta de nuevas topologías que extienden el rango de tensión y potencia de operación en comparación con tecnologías y topologías de circuitos actuales. Se proponen PMCs basados en TFET para fuentes de RF y DC y se identifican las limitaciones (con soluciones) de la utilización de TFETs en convertidores elevadores convencionales basados en inductores.
Hi ha hagut una tremenda evolució en la tecnologia de circuits integrats en les últimes dècades. Amb l'escalat de transistors de metall-òxid-semiconductor (CMOS), s'han fet possibles xips més ràpids, amb menys consum d'energia i més complexos amb menys àrea i això ha possibilitat l'existència dels aparells electrònics que veiem en l'actualitat. La creixent demanda de portabilitat implica que el consum d'energia és un indicador clau en el disseny analògic i digital. Mentre que el consum de potència dinàmica disminueix quadràticament amb la disminució de la tensió de font d'alimentació, la potència de fuites presenta una limitació a causa del pendent sub-llindar invers (sub-threshold slope, SS). Una reducció de la tensió d'alimentació implica una conseqüent reducció de tensió llindar a fi de mantenir les prestacions que, donat el SS fix, causa un augment exponencial del corrent de fuita. Això planteja una limitació en la reducció de consum d'energia que és inherent als transistors convencionals basats en injecció de portadors termoiònics (MOSFETS i FinFETs). En transistors termoiònics la SS a temperatura ambient està limitat a 60 mV / dec. Per eludir la limitació SS de transistors convencionals es requereixen dispositius amb mecanismes diferents d'injecció de portadors. El transistor túnel d'efecte camp (TFET) es presenta com la tecnologia més prometedora a causa del seu mecanisme d'injecció de portadors no tèrmic basat en l'efecte Band-To-Band Tunneling (BTBT). Els TFETs es coneixen com a dispositius d'alt pendent sots-llindar (SS <60 mV / dec a temperatura ambient). Han estat ja demostrats guanys de corrent gran (ION / IOFF> 10 ^ 5) en operació de baixa tensió (sub-0,25 V) i un corrent de fuites extremadament baix, col·locant els TFETs com a seriosos candidats per a aplicacions de circuits eficients d'ultra-baixa potència i energia. Els TFETs s'han explorat sobretot en circuits digitals i aplicacions. En aquesta tesi, l'ús de TFETs s'explora com una tecnologia alternativa també per a circuits de potència i de conversió de tensió ultra-baixes, adequada per a fonts d'energia de l'ambient, usualment molt limitades en magnitud. Degut a que els TFETs estan dissenyats com díodes p-i-n en polarització inversa (hi ha diferent tipus de dopatge en les regions font / drenador), les seves característiques elèctriques particulars en condicions de polarització inversa requereixen canvis en les topologies de circuit convencionals. En la tesi, rectificadors, bombes de càrrega i circuits de gestió de l'energia (PMC) amb TFETs es dissenyen i analitzen, realitzant una avaluació del seu rendiment amb la proposta de noves topologies que estenen el rang de tensió i potència d'operació en comparació amb tecnologies i topologies de circuits actuals. Es proposen PMCs basats en TFET per fonts de RF i DC i s'identifiquen les limitacions (amb solucions) de la utilització de TFETs en convertidors elevadors convencionals basats en inductors.
5
Meng, Ping [Verfasser]. "Solid-solid recuperation to improve the energy efficiency of tunnel kilns / Ping Meng." Magdeburg : Universitätsbibliothek Magdeburg, 2011. http://d-nb.info/101134260X/34.
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6
Wang, Jialin. "Building integrated wind energy." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/building-integrated-wind-energy(81978798-e68a-4189-87b0-4159b280b6e9).html.
Повний текст джерелаАнотація:
In considering methods of reducing the emission of carbon dioxide; there is a growing interest for use of wind power at domestic building in U.K. But the technology of wind turbines development in building environment is more complicated than in open areas. Small wind turbines in suburban areas have been reported as having unsatisfactory energy output, but it is not clear whether this is due to insufficient wind resource or low turbine efficiency. The aim of this research is to discover whether the wind resource in suburban areas is large enough for small wind turbines to produce a useful energy output.Historical wind data and manufacturers' turbine characteristics were used to estimate the hourly wind speed and energy output for different U.K. cities, terrain zones and turbines. It was found that for turbines at 10 m height in suburban areas and depending on city, the annual wind energy conversion efficiency ranged from about 20 to 40%, while the number of turbines required to produce the annual average electricity consumption of a UK dwelling ranged from about 6 for the smallest turbine (5.3 m² rotor area) to about 1 for the largest (35.26 m² rotor area).This analysis was based on average conditions, but the wind speed near buildings can vary considerably from one point to another. In order to predict the performance of wind turbines more accurately, the atmospheric boundary layer (ABL) of suburban areas was simulated in both CFD and wind tunnel models, and models of groups of semi-detached and terraced houses were set in this ABL. It was found that at 10 m height in the area of the houses, the turbulence intensity was too high for satisfactory operation of wind turbines (19 to 35%) while the mean velocity at different points ranged from 86 to 108% of the 10m reference velocity. At 30m height the turbulence intensity was satisfactory (less than 19 %), while the mean velocity ranged from 92 to 103 % of the 30 m reference velocity. It is concluded that for wind turbines in suburban areas, at 10 m height the wind speed is too low and the turbulence is too high for satisfactory performance, while at 30 m height the wind speed is much higher and the turbulence is low enough.
7
Desmond, Cian. "The consideration of forestry effects in wind energy resource assessment." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16169.
Повний текст джерелаАнотація:
Research focused on the reduction of uncertainties when considering the wind resource in the vicinity of forestry. This thesis examined the use of high density laser scanning technology to capture the structure of forest canopies along with the measurement of thermal effects using sonic anemometry. Methodologies were then developed to include these high quality data in Computational Fluid Dynamics software in order to allow the complex nature of forestry flows to be considered analytically.
8
Wang, Fa. "Wind Farm Control for Optimal Power Generation and Fatigue Reduction: Strategies and Experimentation in Wind Tunnel." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491350425071592.
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Campos-Arriaga, Liliana. "Wind energy in the built environment : a design analysis using CFD and wind tunnel modelling approach." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10806/.
Повний текст джерелаАнотація:
Renewable energies are a critical element for reducing greenhouse gases emissions and achieving a sustainable development. Until recently, building integration of renewable sources was focused on solar technologies. Nevertheless,building integrated wind turbines can and must be part of the solution to the global energy challenge. This research investigated the potential of integrating small vertical wind turbines between medium-rise buildings. Wind velocities were measured around 7 fifteenstorey towers. The measurements were carried out for nine different configurations,using a boundary layer wind tunnel and computational fluid dynamics (CFD) simulations. Computed and measured results showed reasonable agreement. The differences were more apparent at ground level. It was established that building orientation and the separation between buildings defines to a great extent the wind environment around buildings. It was found that a distance between buildings of 15 metres and an orientation of θ=260˚ produced the higher augmentation factors. This configuration produced up to 17,812kWh in a typical Nottingham UK year, using six vertical wind turbines of 2.5kW each. Results suggested that the use of CFD as a visualisation tool is extremely useful at design stages in projects involving the integration of wind turbines. Nevertheless, the results of CFD simulations are highly dependent on the type of roughness modification applied to the wall functions, the choice of the turbulence model and the modelling of the inlet wind velocity profile. Because servicing buildings accounts for around half of the UK’s total energy consumption, the need to reduce the consumption of fossil fuels is central to good building design. That is why the architectural practice must respond professionally by delivering buildings that successfully integrate wind energy technologies, which can only be achieved if the designer actively engages with the environmental design principles and improves his understanding of building physics.
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Barassa, Jonathan, and Rickard Nordlöf. "Numerical Study on Air Demand of Free Surface Flows in a Discharge Tunnel." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414989.
Повний текст джерелаАнотація:
Aeration issued through a ventilation shaft is an important measure to prevent cavitation and large gauge pressure in flood discharge tunnels. In order to dimension the ventilation shaft appropriately, itis necessary to have a good understanding of the air-water flow in the tunnel. In this study, the multiphase flow through a discharge tunnel was simulated in the computational fluid dynamics (CFD) software ANSYS Fluent. Since the flow was separated, the simulation setup used the volume of fluid (VOF) multiphase model, that could track the water surface. Furthermore, the so called RNG k-epsilon turbulence model was used. The CFD model was validated with measured data provided from two open channel experiments carried out on a scaled model at Sichuan University. To ensure mesh independence, grid convergence index (GCI)studies were performed for the two validating cases. After the validation, a top wall and a ventilation shaft was added to the CFD model. The flow was then simulated for four different shaft designs and four different water inlet velocities. The air demand and air supply for the various scenarios could thereby be calculated. The results of this study were also compared with previous research on multiphase flow through tunnels with similar design. It was concluded that the air flow downstream in the tunnel converged for the two larger designs. It was also concluded that the air demand in the tunnel was satisfied for the larger ventilation shafts. A smaller study on cavitation was made and the risk was considered non-existent for all the simulated cases.
11
Ying, Pei. "Aerodynamic analysis of a novel wind turbine for an omni-flow wind energy system." Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17355.
Повний текст джерелаАнотація:
The purpose of this research is to propose a novel wind turbine for an omni-flow wind energy system and investigate its aerodynamic performance. The geometry of the novel wind turbine is based upon the impulse turbine technology which has been successful in wave energy. In this study, both numerical and experimental studies were conducted to evaluate the aerodynamic features of this wind turbine. The numerical method was validated by a comparison between numerical and experimental results over a range of tip speed ratios. Results obtained from experiments and simulations indicate that the proposed wind turbine can be employed. Additionally, on the basis of the analyses performed, this new wind turbine has the potential for having a good startup feature, which means that this wind turbine can be suitable for applications in an urban environment. As an important component, the stator of this wind turbine can increase the passing flow velocity by 20%. Meanwhile, the passing flow direction also can be optimised by the stator. Aerodynamics of the wind turbine was analysed under the non-uniform flow condition, because the flow is non-uniform inside the omni-flow wind energy system. It was found that the maximum power coefficient of such a turbine under the non-uniform flow condition is lower than that under the uniform flow condition. Due to the non-uniform flow, the blades experience different flow velocities, and as a consequence, undergo different aerodynamic loads during one operation cycle. Thus the generated torque and thrust on a blade are subjected to frequent and periodical changes. Influences of the geometrical parameters on the aerodynamic characteristics of this wind turbine were investigated. From the initial study, it was found that changes of hub-to-tip ratios, numbers of blades, aerofoils and numbers of guide vanes, can significantly affect the II power performance. Additionally, the wind turbine obtained high values of maximum torque coefficients with changing geometrical parameters.
12
Conan, Boris. "Wind resource accessment in complex terrain by wind tunnel modelling." Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00843645.
Повний текст джерелаАнотація:
To benefit from strong winds, an increasing number of wind turbines are placed in complex terrains. But complex terrains means complex flows and difficult wind resource assessment. This study proposed to use wind tunnel modelling to evaluate the wind in a complex topography. The goal of this study is to evaluate the possibilities of wind resources assessment by wind tunnel modelling and to quantify the important modelling parameters. The lower part of the atmosphere, the atmospheric boundary layer (ABL) is defined by a velocity and a turbulence gradient. The ABL is reproduced in the wind tunnel by placing obstacles and roughness elements of different size representative to the type of terrain desired. The flow produced in the wind tunnel is validated against field data and a wise choice of the obstacles is discussed to reproduce the desired wind profile. The right reproduction of the inflow conditions is found to be the most important parameter to reproduce. The choice of the area to reproduce around a site in usually difficult to make in order to keep a low scaling factor and to account for the surrounding topography. A series of tests on simplified hills helps the experimentalist in this choice by enlightening the longitudinal and vertical extension of the wake downstream different hills shapes. Finally, two complex topographies are studied in two wind tunnels, the Bolund hill in Denmark and the Alaiz mountain in Spain. The results are giving good results, 5 to 10 %, for predicting the wind speed but more scatter is observed for the modelling of the turbulence, up to 100 %. The laboratory simulation of atmospheric flows proves to be a demanding but reliable tool for the prediction of the mean wind speed in complex terrain.
13
Martin, Michel. "Étude expérimentale de bolomètres rapides à jonctions tunnel métal normal-isolant-supraconducteur." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0206.
Повний текст джерелаАнотація:
Nous etudions des bolometres bases sur des jonctions tunnel metal normal - isolant - supraconducteur en vue de leur application a la mesure d'energie d'ions retrodiffuses. La fabrication et l'etude de tels bolometres est montre en detail. On s'attache particulierement a l'influence des parametres physiques sur la mesure de temperature.
14
Liu, Jheng-Sin. "Advanced Energy-Efficient Devices for Ultra-Low Voltage System: Materials-to-Circuits." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/81858.
Повний текст джерелаАнотація:
The overall energy consumption of portable devices has been projected to triple over the next decade, growing to match the total power generated by the European Union and Canada by 2025. The rise of the internet-of-things (IoT) and ubiquitous and embedded computing has resulted in an exponential increase in such devices, wherein projections estimate that 50 billion smart devices will be connected and online by 2020. In order to alleviate the associated stresses placed on power generation and distribution networks, a holistic approach must be taken to conserve energy usage in electronic devices from the component to the circuit level. An effective approach to reduce power dissipation has been a continual reduction in operating voltage, thereby quadratically down-scaling active power dissipation. However, as state-of-the-art silicon (Si) complimentary metal-oxide-semiconductor (CMOS) field-effect transistors (FETs) enter sub-threshold operation in the ultra-low supply voltage regime, their drive current is noticeable degraded. Therefore, new energy-efficient MOSFETs and circuit architectures must be introduced. In this work, tunnel FETs (TFETs), which operate leveraging quantum mechanical tunneling, are investigated. A comprehensive investigation detailing electronic materials, to novel TFET device designs, to memory and logic digital circuits based upon those TFETs is provided in this work. Combined, these advances offer a computing platform that could save considerable energy and reduce power consumption in next-generation, ultra-low voltage applications.Ph. D.
15
Semakala, Chanel, and Emre Cömert. "En jämförande studie mellan diesel- och eldrivna tunneldrivningsmaskiner för masshantering i tunnel." Thesis, KTH, Byggteknik och design, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-253778.
Повний текст джерелаАнотація:
The construction industry is facing a reality where the dependency on fossil fuels needs to cease and be replaced by options that are more climate friendly. One such option is the electrification that has not made a breakthrough in the construction industry yet and therefore needs to be examined. In this thesis an investigation is made by two different systems of wheel loaders and trucks. One system that conducts machines run by electricity and another one where the system is powered by diesel. The investigation is based on goal formulation which serves as the basis for answering these questions. The machines were examined in such as to obtain results that illustrate which system of machines that are profitable with regards to time, energy consumption, carbon dioxide emissions and total costs. This thesis has also as an intent to identify any advantages and disadvantages of each transport method. This is done in order to lend structure to any further research conducted in the future. To be able to compare and examine the properties of the machines, these machines were applied to a tunneling project. The project that was received was the metro station Hagalunds industriområde. The planned expansion of the subway will lead to a new metro line between Arenastaden and Odenplan, where Hagalunds industriområde will become an intermediate station. In order to truly optimize our efforts and carry out the calculations, the focus was placed on a partial stretch of 1 000 meters with respect to the main tunnel and working tunnel. The result obtained shows that the electric wheel loader leads to less time, carbon dioxide emissions and better energy efficiency than the diesel-powered wheel loader. On the other hand, the disadvantage is that the purchase cost of the electric wheel loader leads to greater total costs. These investments may be necessary to break the dependence on fossil fuels. When comparing the trucks, the result showed that the electric truck is a better alternative from an environmental perspective and total costs. While the diesel-powered truck saves on both time and energy. The reason why the total cost of the diesel-powered truck differs greatly from the electricpowered truck is the rental costs. If the diesel-powered truck was instead purchased, the total cost difference could be reduced.Bygg- och anläggningssektorn står inför en verklighet där beroendet av fossila bränslen behöver brytas och ersättas med miljövänligare alternativ. Ett sådant alternativ är elektrifieringen som inte riktigt har slagit igenom för anläggningssektorn och därför behöver undersökas. I detta examensarbete undersöks två olika system av hjullastare och lastbilar. Ett system där maskinerna drivs med el och ett annat system med maskiner som drivs på diesel. Undersökningen hade målformuleringen som utgångspunkt för att besvara frågeställningarna. Maskinerna granskades för att erhålla ett resultat som visar vilket system av maskiner som är lönsammare att använda med avseende på tidsåtgång, energiförbrukning, koldioxidutsläpp samt totala kostnader. Examensarbetet har även som syfte att redogöra eventuella för-och nackdelar för respektive transportmetod. Detta för att ge ytterligare underlag till vidare forskning. För att kunna jämföra och undersöka maskinernas egenskaper applicerades dessa maskiner på ett tunneldrivningsprojekt. Projektet som erhölls var tunnelbanestationen Hagalunds industriområde. Den planerade utbyggnaden av tunnelbanan kommer att leda till en ny tunnelbanelinje mellan Arenastaden och Odenplan, där Hagalunds industriområde kommer bli en mellanliggande station. För att avgränsa arbetet och genomföra beräkningarna lades fokus på en delsträcka om 1 000 meter med avseende på huvudtunnel och arbetstunnel. Resultatet som erhölls visar att den eldrivna hjullastaren leder till mindre tidsåtgång, koldioxidutsläpp och bättre energieffektivitet än den dieseldrivna hjullastaren. Däremot är nackdelen att inköpskostnaden för den eldrivna hjullastaren leder till större totala kostnader. Dessa investeringar kan vara nödvändiga att vidta för att beroendet av fossila bränslen ska brytas. Vid jämförelse av lastbilarna visade resultatet att den eldrivna lastbilen är ett bättre alternativ ur miljöperspektiv och totala kostnader. Medan den dieseldrivna lastbilen sparar på både tid och energi. Anledningen till att totala kostnaden för dieseldrivna lastbilen skiljer sig mycket från den eldrivna lastbilen är hyreskostnaderna. Om den dieseldrivna lastbilen istället köptes in, kunde den totala kostnadsskillnaden reduceras.
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Ohm, Thorsten. "Effet tunnel quantique de l'aimantation dans un aimant moleculaire, Fe8." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10187.
Повний текст джерелаАнотація:
Nous avons étudié les retournements d'aimantation par effet tunnel quantique dans des aimants moléculaires. Nos expériences montrent clairement l'effet tunnel quantique dans l'aimant moléculaire Fe8. Ce système se compose d'un ensemble d'aimants nanoscopiques identiques et orientes parallèlement. Chacune des molécules porte un spin s = 10. Les mesures de relaxation sont faites en utilisant des magnétomètres à squid aux performances uniques. Ces magnétomètres permettent des mesures de haute sensibilité en champ fort, jusqu'a 8 tesla, et aux très basses températures (>50 mK). A haute température le système Fe8 se comporte comme un système superparamagnetique qui relaxe par activation thermique au-dessus d'une barrière de 24 K. Au-dessous de 0,4 K la relaxation est indépendante de la température ce qui est le signe d'un effet tunnel quantique du spin moléculaire à travers la barrière. Le temps de relaxation varie fortement avec le champ externe et montre des effets résonants. Dans le régime quantique la courbe de relaxation est non-exponentielle et bien décrite par une exponentielle étirée. Le début de la courbe de relaxation suit une loi en racine carrée du temps. Nous montrons que le champ dipolaire entre les molécules a une forte influence sur la relaxation mais le champ dipolaire n'agit pas comme une force : il permet ou empêche l'effet tunnel quantique dans une molécule. Nous présentons un modelé phénoménologique simple qui explique pourquoi la courbe de relaxation ressemble à une exponentielle étirée. Dans ce modèle nous supposons que chaque molécule a une résonance très étroite et que la distribution du champ local évolue pendant la relaxation. De plus, nous présentons un calcul numérique sur l'évolution de la distribution du champ local. Un calcul de Monte-Carlo avec des distributions réalistes montre lui aussi l'existence de corrélations inhabituelles en accord qualitatif avec nos observations.
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Perraud, Simon. "Etude de puits quantiques semiconducteurs par microscopie et spectroscopie à effet tunnel". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00606632.
Повний текст джерелаАнотація:
Des puits quantiques à base d'hétérostructures In0.53 Ga0.47 As/In0.52 Al0.48 As, fabriqués par épitaxie par jets moléculaires sur substrats InP(111)A, sont étudiés par microscopie et spectroscopie à effet tunnel à basse température et sous ultra-vide. La première partie est consacrée à une étude de la surface épitaxiée (111)A de In0.53 Ga0.47 As de type n. Il est découvert que le niveau de Fermi de surface est positionné dans la bande de conduction, à proximité du niveau de Fermi de volume, et peut être partiellement contrôlé en variant la concentration d'impuretés de type n dans le volume. Ce résultat est confirmé en déterminant la relation de dispersion de la bande de conduction en surface. Un tel dépiégeage partiel du niveau de Fermi de surface indique que la densité d'états de surface accepteurs est faible. Il est proposé que ces états proviennent de défauts ponctuels natifs localisés à la surface. La deuxième partie, basée sur les résultats obtenus dans la première partie, est consacrée à une étude de puits quantiques In0.53 Ga0.47 As de surface, déposés sur des barrières In0.52 Al0.48 As selon la direction (111)A. Les mesures sont conduites sur la surface épitaxiée (111)A du puits quantique In0.53 Ga0.47 As, de manière à pouvoir sonder à l'échelle du nanomètre la distribution de densité locale d'états électroniques dans le plan du puits quantique. Il est confirmé que des sous-bandes électroniques sont formées dans le puits quantique, et que la concentration d'électrons dans le puits peut être contrôlée du fait du dépiégeage partiel du niveau de Fermi de surface. Il est découvert qu'un phénomène de percolation d'états localisés survient dans la queue de chaque sous-bande, ce qui indique la présence d'un potentiel désordonné dans le puits quantique. Les seuils de percolation sont déterminés en utilisant un modèle semi-classique. L'origine du potentiel désordonné est attribuée à une distribution aléatoire des défauts ponctuels natifs à la surface du puits quantique. Il est également découvert qu'un état lié apparaît au bas de chaque sous-bande à proximité d'un défaut ponctuel natif de type donneur. L'énergie de liaison et le rayon de Bohr des états liés peuvent être directement déterminés. De plus, il est démontré que l'énergie de liaison et le rayon de Bohr sont fonctions de l'épaisseur du puits quantique, en accord quantitatif avec des calculs variationnels d'impuretés dans le modèle de l'atome d'hydrogène.
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Di, Nicola Federico. "Energy harvesting from piezoelectric devices embedded in a 3D printed wing." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9705/.
Повний текст джерелаАнотація:
This thesis work has been carried out at Clarkson University in Potsdam NY, USA and involved the design of a low elongation wing, consisting of parts made by polylactide (PLA) using the fused deposition model (FDM) technology of Rapid Prototyping, then assembled together in a thin aluminum spar. The aim of the research is to evaluate the feasibility of collecting electrical energy by converting mechanical energy from the vibration of the wing flutter. With this aim piezoelectric stripes were glued in the inner part of the wing, as well as on the aluminum spar, as monomorphic configuration.
During the phases of the project, particular attention was given to the geometry and the materials used, in order to trigger the flutter for low flow velocity.
The CAD software SolidWorks® was used for the design of the wing and then the drawings were sent to the Clarkson machine shop in order to to produce the parts required by the wing assembly.
FEM simulations were performed, using software MSC NASTRAN/PATRAN®, to evaluate the stiffness of the whole wing as well as the natural vibration modes of the structure. These data, in a first approximation, were used to predict the flutter speed.
Finally, experimental tests in the Clarkson wind tunnel facility were carried out in order to validate the results obtained from FEM analysis. The power collected by the piezoelectrics under flutter condition was addressed by tuning the resistors downstream the electronic circuit of the piezoelectrics.
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Celesin, Michael Enoch. "Application and Characterization of Self-Assembled Monolayers In Hybrid Electronic Systems." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4875.
Повний текст джерелаАнотація:
In this study, we explore ultra-thin insulators of organic and inorganic composition and their potential role as high-speed rectifiers. Typical applications for these structures include IR sensing, chemical detection, high speed logic circuits, and MEMS enhancements. While there are many elements in the functional group required to create a rectifying antenna (rectenna), the primary thrust of this work is on the rectifier element itself.
To achieve these research goals, a very good understanding of quantum tunneling was required to model the underlying phenomenon of charge conduction. The development of a multi-variable optimization routine for tunneling prediction was required. MATLAB was selected as the programming language for this application because of its flexibility and relative ease of use for simulation purposes. Modeling of physical processes, control of electromechanical systems, and simulation of ion implantation were also to be undertaken.
To advance the process science, a lithographic mask set was made which utilized the information gleaned from the theoretical simulations and initial basic experiments to create a number of diode test structures. This came to include the creation of generations of mask sets--each optimizing various parameters including testability, alignment, contact area, device density, and process ease. Following this work, a complete toolset for the creation of "soft" contact top metals was required and needed to be developed. Ultra-flat substrates were needed to improve device reliability and measurement consistency.
The final phase of research included measurement and characterization of the resultant structures. Basic DC electrical characterization of the organic monolayers would be accomplished using metal probes. Statistical studies of reliability and process yield could then easily be carried out. The rectification ratio (ratio of forward over reverse current at a given voltage magnitude) was found to be a reliable indicator of diode performance in the low frequency ranges. This would mean writing additional code in MATLAB to assist in the automatic analysis for the acquired IV curves. Progression to AC / RF measurements of tunneling performance was to be accomplished using relatively low frequencies (below 100 MHz). Finally, the organic films themselves would be studied for consistency, impedance characteristics, incidence of defects, and thickness by a variety of metrology techniques.
This project resulted in a number of advances to the state-of-the-art in nanofabrication using organic monolayers. A very detailed review of the state of alkanethiol research was presented and submitted for publication. A single pot technique was developed to softly deposit metal nanoparticles onto a charged surface with a high degree of control. A temporary contact method using pure, sub-cooled gallium liquid metal was used to probe organic monolayers and plot IV curves with better understanding of surface states than before. An inkjet printer solution was devised for top contact printing which involved the development and production of a work-up free insulator ink which is water soluble and printable to resolutions of about 25 um. Localized selective chemical crosslinking was found to reduce printed ink solubility following deposition. Future work will likely include additional exploration of crosslinkable Langmuir-Blodgett films as MIM insulators. Stability and testing will hinge on the fabrication of enclosures or packages for environmental isolation.
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Du, Yingkang. "An Orthogonal Savonius-type Wind Turbine: Design and Experiments." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1459510710.
Повний текст джерела
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OLIVIERI, STEFANO. "Elastically-bounded flapping plates for flow-induced energy harvesting." Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/999997.
Повний текст джерелаАнотація:
This work concerns a novel concept for energy harvesting (EH) from fluid flows, based on the aeroelastic flutter of elastically-bounded plates immersed in laminar flow. The resulting flapping motions are investigated in order to support the development of centimetric-size EH devices exploiting low wind velocities, with potential application in the autonomous powering of low-power wireless sensor networks used, e.g., for remote environmental monitoring. The problem is studied combining three-dimensional direct numerical simulations exploiting a state-of-the-art immersed boundary method, wind-tunnel experiments on prototypal EH devices, and a reduced-order phenomenological model based on a set of ordinary differential equations. Three key features of the aeroelastic system are investigated: (i) we identify the critical condition for self-sustained flapping using a simple balance between characteristic timescales involved in the problem; (ii) we explore postcritical regimes characterized by regular limit-cycle oscillations, highlighting how to maximize their amplitude and/or frequency and in turns the potential energy extraction; (iii) we consider arrays of multiple devices, revealing for certain arrangements a constructive interference effect that leads to significant performance improvements. These findings lead to an improved characterization of the system and can be useful for the optimal design of EH devices. Moreover, we outline future research directions with the ultimate goal of realizing high-performance networks of numerous harvesters in real-world environmental conditions.
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Swift, Angela Marion. "The development of a cryogenic phonon detector, based on the coupling of superconducting tunnel junctions to indium antimonide crystals : with applications in X-, #gamma#- and #beta#-ray spectroscopy antimonide." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294274.
Повний текст джерела
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Garré, Saulo de Oliveira. "Avaliação experimental do desempenho aerodinâmico de pequenas turbinas eólicas confeccionadas em prototipagem 3D." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/132643.
Повний текст джерелаАнотація:
Este trabalho apresenta a avaliação experimental em túnel aerodinâmico de características de dois aerogeradores de pequeno porte com cinco pás. Para isso, utilizando-se prototipagem 3D, construíram-se dois modelos em escala reduzida, os quais foram avaliados primeiramente utilizando-se Pás Ótimas de Betz e depois Pás Ótimas de Betz Modificadas. Antes de se avaliar o equipamento determinou-se a distribuição de velocidades na seção transversal do túnel com o auxílio de um tubo de Pitot. Com o perfil de velocidades do túnel conhecido, determina-se o torque estático do protótipo com o uso de um torquímetro digital acoplado ao eixo do equipamento, que registrou todas as leituras para as faixas de velocidade de 1 m/s até 9,88 m/s. Também com o torquímetro avalia-se a influência da posição angular das pás no torque medido. Para tanto, elas são projetadas móveis no hub, o que possibilitou variar sua angulação em relação ao escoamento, mudando assim o ângulo de ataque e, por conseguinte o torque produzido. Empregou-se um foto tacômetro para medir a rotação do modelo em giro livre. Com os dados obtidos, determina-se a curva de torque estático e a curva de RPM em função da velocidade incidente. Através da determinação experimental do perfil de velocidade incidente e do perfil de velocidade na esteira aerodinâmica de cada turbina é avaliada a variação da quantidade de movimento do escoamento e determinada a potência extraída pelos rotores em rotação livre. Este estudo visa contribuir com o projeto de um aerogerador real, prevendo as características aerodinâmicas que o equipamento apresentará se construído com o presente layout. Com os dados analisados se faz uma previsão para as curvas de potência dos protótipos. Os resultados experimentais de torque e potência demonstram boa aproximação com os resultados obtidos por avaliação analítica pelo método do elemento de pá. A prototipagem 3D administrada se mostrou eficaz traduzindo realismo e excelente custo-benefício. A turbina construída com Pás Ótimas de Betz apresentou torque estático 17,8% superior à construída com as Pás Modificadas e extraiu 22% a mais de potência do escoamento de ar.This paper presents the experimental evaluation in wind tunnel of two small wind turbines features five blades. Therefore, using 3D prototyping, two models were built on a reduced scale, which were first evaluated using Optimal Blade Betz and Optimal Blade Betz Modified. Prior to evaluating the distribution machine at speeds determined in the tunnel cross-section with the aid of a Pitot tube. With the known tunnel velocity profile, determines the static torque of the prototype with the use of a digital torquimeter coupled to the machine axis, which recorded all the readings for the speed range of 1 m/s to 9,88 m/s. Also with the torquimeter evaluates the influence of the angular position of the blades in the measured torque. Therefore, it is mobile designed in the hub, allowing vary their angle in the outflow, thereby changing the angle of attack and therefore the torque produced. Employed a photo tachometer for measuring the rotation of the model in free spin. With the data, determines the static torque curve and RPM curve as a function of incident speed. Through experimental determination of the incident velocity profile and the velocity profile in the aerodynamic wake of each turbine is evaluated the variation of the amount of movement of the flow and determined the power extracted by the rotor in free rotation. This study aims to contribute to the design of a real wind turbine informing the aerodynamic characteristics of the equipment shall be constructed with this layout. With the data analyzed to make a prediction for the prototype power curves. The experimental results demonstrate torque and power good approximation to the results obtained by evaluation by analytical element of the paddle method. The turbine constructed with Optimal Betz Blades presented static torque 17,8% higher than constructed with the Modified Blades and extracted 22% more power air outflow.
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Sharma, Saumya. "Design, Fabrication and Characterization of MIM Diodes and Frequency Selective Thermal Emitters for Solar Energy Harvesting and Detection Devices." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5579.
Повний текст джерелаАнотація:
Energy harvesting using rectennas for infrared radiation continues to be a challenge due to the lack of fast switching diodes capable of rectification at THz frequencies. Metal insulator metal diodes which may be used at 30 THz must show adequate nonlinearity for small signal rectification such as 30 mV. In a rectenna assembly, the voltage signal received as an output from a single nanoantenna can be as small as ~30µV. Thus, only a hybrid array of nanoantennas can be sufficient to provide a signal in the ~30mV range for the diode to be able to rectify around 30THz. A metal-insulator-metal diode with highly nonlinear I-V characteristics is required in order for such small signal rectification to be possible. Such diode fabrication was found to be faced with two major fabrication challenges. The first one being the lack of a precisely controlled deposition process to allow a pinhole free insulator deposition less than 3nm in thickness. Another major challenge is the deposition of a top metal contact on the underlying insulating thin film. As a part of this research study, most of the MIM diodes were fabricated using Langmuir Blodgett monolayers deposited on a thin Ni film that was sputter coated on a silicon wafer. UV induced polymerization of the Langmuir Blodgett thin film was used to allow intermolecular crosslinking. A metal top contact was sputtered onto the underlying Langmuir Blodgett film assembly. In addition to material characterization of all the individual films using IR, UV-VIS spectroscopy, electron microscopy and atomic force microscopy, the I-V characteristics, resistance, current density, rectification ratio and responsivity with respect to the bias voltage were also measured for the electrical characterization of these MIM diodes.
Further improvement in the diode rectification ratio and responsivity was obtained with Langmuir Blodgett films grown by the use of horizontally oriented organic molecules, due to a smaller tunneling distance that could be achieved in this case. These long chain polymeric molecules exhibit a two-dimensional molecular assembly thereby reducing the tunneling distance between the metal electrodes on either side of the insulating layer. Rectification ratios as high as 450:1 at ±200mV were obtained for an MIM diode configuration of Ni-LB films of Arachidic Acid films-(Au/Pd).
The bandwidth of the incident radiation that can be used by this rectenna assembly is limited to 9.5% of 30THz or ±1.5THz from the center frequency based on the antenna designs which were proposed for this research. This bandwidth constraint has led to research in the field of frequency selective emitters capable of providing a narrowband emission around 30THz.
Several grating structures were fabricated in the form of Ni-Si periodic arrays, in a cleanroom environment using photolithography, sputtering and deep reactive ion etching. These frequency selective samples were characterized with the help of focusing optics, monochromators and HgCdTe detectors. The results obtained from the emission spectra were utilized to calibrate a simulation model with Computer Simulation Technology (CST) which uses numerous robust solving techniques, such as the finite element method, in order to obtain the optical parameters for the model. Thereafter, a thorough analysis of the different dimensional and material parameters was performed, to understand their dependence on the emissivity of the selective emitter.
Further research on the frequency selectivity of the periodic nano-disk or nano-hole array led to the temperature dependence of the simulated spectra, because the material parameters, such as refractive index or drude model collision frequency, vary with temperature. Thus, the design of frequency selective absorbers/emitters was found to be significantly affected with temperature range of operation of these structures.
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Zakaria, Mohamed Yehia. "Unsteady Nonlinear Aerodynamic Modeling and Applications." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/79909.
Повний текст джерелаАнотація:
Unsteady aerodynamic modeling is indispensable in the design process of rotary air vehicles, flapping flight and agile unmanned aerial vehicles. Undesirable vibrations can cause high-frequency variations in motion variables whose effects cannot be well predicted using quasi-steady aerodynamics. Furthermore, one may exploit the lift enhancement that can be generated through an unsteady motion for optimum design of flapping vehicles. Additionally, undesirable phenomena like the flutter of fixed wings and ensuing limit cycle oscillations can be exploited for harvesting energy. In this dissertation, we focus on modeling the unsteady nonlinear aerodynamic response and present various applications where unsteady aerodynamics are very relevant.
The dissertation starts with experiments for measuring unsteady loads on an NACA-0012 airfoil undergoing a plunging motion under various operating conditions. We supplement these measurements with flow visualization to obtain better insight into phenomena causing enhanced lift. For the model, we present the frequency response function for the airfoil at various angles of attack. Experiments were performed at reduced frequencies between 0.1 and 0.95 and angles of attack up to 65 degrees. Then, we formulate an optimization problem to unify the transfer function coefficients for each regime independently to obtain one model that represents the global dynamics. An optimization-based finite-dimensional (fourth-order) approximation for the frequency responses is developed. Converting these models to state-space form and writing the entries of the matrices as polynomials in the mean angle of attack, a unified unsteady model was developed. In the second set of experiments, we measured the unsteady plunging forces on the same airfoil at zero forward velocity. The aim is to investigate variations of the added forces associated with the oscillation frequency of the wing section for various angles of attack. Data of the measured forces are presented and compared with predicted forces from potential flow approximations. The results show a significant departure from those estimates, especially at high frequencies indicating that viscous effects play a major role in determining these forces.
In the second part of this dissertation, we consider different applications where unsteady loads and nonlinear effects play an important role. We perform a multi-objective aerodynamic optimization problem of the wing kinematics and planform shape of a Pterosaur replica ornithopter. The objective functions included minimization of the required cycle-averaged aerodynamic power and maximization of the propulsive efficiency. The results show that there is an optimum kinematic parameter as well as planform shape to fulfill the two objectives. Furthermore, the effects of preset angle of attack, wind speed and load resistance on the levels of harvested power from a composite beam bonded with the piezoelectric patch are determined experimentally. The results point to a complex relation between the aerodynamic loading and its impact on the static deflection and amplitudes of the limit cycle oscillations as well as the level of power harvested. This is followed by testing of a centimeter scale micro wind turbine that has been proposed to power small devices and to work as a micro energy harvester. The experimental measurements are compared to predicted values from a numerical model.
The methods developed in this dissertation provide a systematic approach to identifying unsteady aerodynamic models from numerical or experimental data that may work within different regimes. The resulting reduced-order models are expressed in a state-space form, and they are, therefore, both simple and efficient. These models are low-dimensional linear systems of ordinary differential equations so that they are compatible with modern flight dynamic models. The specific form of the obtained added force model, which defines the added forces as a function of plunging velocity and drag forces, guarantees that the resulting model is accurate over a range of high frequencies. Moreover, presented applications give a sense of the broad range of application of unsteady aerodynamics.Ph. D.
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Zhang, Xu. "Analysis and optimisation of a novel wind turbine." Thesis, University of Hertfordshire, 2014. http://hdl.handle.net/2299/13897.
Повний текст джерелаАнотація:
The technologies of urban wind turbines have been rapidly developed in recent years, but urban wind turbines have not found a wide application due to the limitations of their designs. The power output of urban wind turbine is significantly affected by urban terrain, which can cause low speed flow with frequent change of its direction. Thus, there is a need for a new wind turbine to meet the requirements of an urban wind turbine. In this study, a novel wind turbine for urban areas was designed and developed. The investigations of the novel urban wind turbine were carried out by using computational fluid dynamic (CFD) simulations and wind tunnel tests. The results from the investigation have shown that the novel wind turbine has a great potential to harvest wind energy in urban areas. A detailed study of effects of each parameter on wind energy concentration of the novel wind turbine was carried out with CFD simulations. According to the simulation results, the shroud structure of the novel wind turbine was modified and the dimensions of the final structure were identified. It was determined that the capability of wind energy concentration of the novel wind turbine shroud has been significantly improved through the structure optimisations. Furthermore, guide vane and impulse turbine were implemented in the novel wind turbine. The flow characteristics through the guide vane was studied and discussed. It was found that the wind flow characteristics can be properly modified by implementing guide vane and the structure of impulse turbine was suitable to be implemented in the novel wind turbine due to the flow characteristic through the guide vane.
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Rüdiger, Jörg. "Feasability of a laterally emitting thin film electroluminescence device as an application specific integrated display." Thesis, Nottingham Trent University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341266.
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Alfadil, Mohammad Omar. "Design Tool for a Ground-Coupled Ventilation System." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100604.
Повний текст джерелаАнотація:
Ground-coupled ventilation (GCV) is a system that exchanges heat with the soil. Because ground temperatures are relatively higher during the cold season and lower during the hot season, the system takes advantage of this natural phenomenon. This research focused on designing a ground-coupled ventilation system evaluation tool of many factors that affect system performance. The tool predicts the performance of GCV system design based on the GCV system design parameters including the location of the system, pipe length, pipe depth, pipe diameter, soil type, number of pipes, volume flow rate, and bypass system. The tool uses regression equations created from many GCV system design simulation data using Autodesk Computational Fluid Dynamics software. As a result, this tool helps users choose the most suitable GCV system design by comparing multiple GCV systems' design performances and allows them to save time, money, and effort.Doctor of Philosophy
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Olsson, Styrbjörn, and Simon Candler. "Payback periods for photovoltaics integrated in nonbuilding structures." Thesis, KTH, Byggteknik och design, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-253817.
Повний текст джерелаАнотація:
In order to provide Sweden and other countries across the globe with energy in a long-term and sustainable manner that accounts for our global environmental goals, we need to adopt more sources of renewable energy. Solar panels and other forms of solar power is one of these renewable energy sources that has a lot of potential and the technology has become increasingly more common in Sweden and other parts of the world in the latest decades. Everyone from private individuals to companies and authorities are increasingly making investments in the technology. With the help of our supervisors and after extensive literature studies we aim to increase the knowledge about solar panels and their economic aspects by calculating and presenting payback periods for solar panels implemented in nonbuilding structures. In conjunction with this we also aim to present a basic theoretical background about solar panels and their global impact to further the understanding of the technology even more. On behalf of, and in collaboration with Trafikverket we have examined the payback periods of four solar panel installations in connection to four of the authority´s nonbuilding structures. Three of these solar installations are applied on technical buildings that are scattered alongside the railway system across the country. The solar panels provide local electricity to the electrical components within the building. The fourth solar installation is connected to a road tunnel where it provides local electricity to the lights within the tunnel. The conducted calculations have resulted in a payback period for each respective solar installation measured in years based on various relevant factors that influence their energy production. Our hope is that this can clarify the economic aspects of the solar panels and be of help in potential future investments in solar power by Trafikverket. The conclusion is that the solar panel installation connected to the road tunnel has the shortest payback period by far and also has great potential to be economically lucrative by generating future revenue. The tree solar installations connected to the technical buildings each have a significantly longer payback period but are still expected to be paid back eventually. However they are not expected to generate a mentionable yield, if any.För att vi ska kunna förse Sverige och resterande delar av världen med energi på ett långsiktigt och hållbart sätt som tar hänsyn till de globala miljömålen krävs det att vi börjar använda mer förnyelsebara energikällor. Solceller och solenergi är en av dessa energikällor som har stor potential och tekniken har under de senaste decennierna blivit allt vanligare både i Sverige och i andra delar av världen. Allt från privatpersoner till företag och myndigheter gör i större och större utsträckning investeringar i tekniken. Med hjälp av litteraturstudier samt stöd från handledare syftar denna avhandling till att öka kunskapen om solceller och deras ekonomiska aspekter genom att beräkna och presentera återbetalningstider för solceller implementerade i anläggningskonstruktioner. I samband med detta kommer en grundläggande teoretisk bakgrund om solceller samt deras globala påverkan att presenteras för att öka förståelsen för ämnet ytterligare. På uppdrag av och i samarbete med Trafikverket har återbetalningstiden för fyra solcellsinstallationer i anslutning till myndighetens anläggningar undersökts. Tre av dessa är teknikhus längs med järnvägen utspridda i olika delar av landet där solcellsinstallationen bidrar med elektricitet till de tekniska komponenterna i huset. Den fjärde installationen ligger i anslutning till en vägtunnel där solcellsinstallationen bidrar med elektricitet till belysningen i tunneln. Resultatet av beräkningarna har gett en återbetalningstid i år för respektive installation baserat på diverse relevanta parametrar som påverkar elproduktionen. Vår förhoppning är att detta kan klargöra de ekonomiska aspekterna av solcellerna samt underlätta för Trafikverket att ta beslut om framtida potentiella solcellsinvesteringar i anslutning till deras anläggningar. Slutsatsen är att solcellsinstallationen i anslutning till vägnätet har den överlägset kortaste återbetalningstiden samt även god potential att bli ekonomiskt lukrativ. De tre installationerna i anslutning till teknikhusen har betydligt längre återbetalningstid och anses så småningom bli återbetalda men utan någon nämnvärd avkastning, om ens någon.
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Kichkie, Nabil. "Comportement dynamique en lacet d'une eolienne a axe horizontal." Paris, ENSAM, 1987. http://www.theses.fr/1987ENAM0007.
Повний текст джерелаАнотація:
Determination de l'influence des parametres geometriques et aerodynamiques sur le comportement dynamique de la machine grace a la resolution du systeme d'equations differentielles qui caracterise le mouvement d'oscillation. Essais en soufflerie sur une maquette a l'echelle 1/3,5 permettant de determiner les couples de rappel ainsi que le coefficient de puissance et le comportement en lacet. Transposition des resultats de la maquette au prototype par l'application des lois de la similitude
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Ebenhoch, Raphael. "Simplified modeling of wind-farm flows." Thesis, KTH, Strömningsfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177309.
Повний текст джерелаАнотація:
Abstact: In order to address the wind-industry's need for a new generation of more advanced wake models, which accurately quantify the mean flow characteristics within a reasonably CPU-time, the two-dimensional analytical approach by Belcher et al. (2003) has been extended to a three-dimensional wake model. Hereby, the boundary-layer approximation of the Navier-Stokes equations has been linearized around an undisturbed baseflow, assuming that the wind turbines provoke a small perturbation of the velocity field. The conducted linearization of the well established actuator-disc theory brought valuable additional insights that could be used to understand the behavior (as well as the limitations) of a model based on linear methods. Hereby, one of the results was that an adjustment of the thrust coecient is necessary in order to get the same wake-velocity field within the used linear framework. In this thesis, two different datasets from experiments conducted in two different wind-tunnel facilities were used in order to validate the proposed model against wind-farm and single-turbine cases. The developed model is, in contrary to current engineering wake models, able to account for effects occurring in the upstream flow region. The measurement, as well as the simulations, show that the presence of a wind farm affects the approaching flow even far upstream of the first turbine row, which is not considered in current industrial guidelines. Despite the model assumptions, several velocity statistics above wind farms have been properly estimated, providing insight about the transfer of momentum inside the turbine rows. Overall, a promising preliminary version of a wake model is introduced, which can be extended arbitrarily depending on the regarded purpose.
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Ciccone, Brianne N. "Modeling of Evaporative Losses in Industrial Pasteurization." Youngstown State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1339587036.
Повний текст джерела
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Abrahamsen, Ida Sinnes. "Wind tunnel model testing of offshore platforms." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18627.
Повний текст джерелаАнотація:
The purpose of this thesis is to highlight some of the areas of interest when it comes to wind tunnel experimenting of offshore platforms regarding stability concerns such as critical angles and wind overturning moment. Some important factors include design of tower geometry, the effect of surface roughness on drag, methods of calculating blockage corrections of wall interference and the generation of an atmospheric boundary layer to resemble full-scale conditions. Data obtained from wind tunnel experiments with two different models have been compared and discussed according to the areas of interest as mentioned above. Testing of platforms was done at NTNU with a six-component balance, measuring forces of drag, side and lift and moment of pitch, roll and yaw with increments of 10° the whole 360° to account for wind coming from all directions. Two geometries were tested for the tower members, one with a circular cross-section which was smaller than scale and another with a square cross-section in correct scale. There was noticeable change in both global forces and moments. Blockage corrections caused by wall interference were researched from different sources and reviewed, and it was apparent that it is still an area with lots of uncertainty. Consensus was that and area ratio of maximum 0.10 should be abided in any case and that the simplified method of Pope is widely used. An atmospheric boundary layer was simulated at NTNU using trial-and-error and the validity of this was confirmed by comparing experimental data with theoretical data regarding the velocity profile, turbulence intensity and energy spectrum. For the experiments of surface roughness on an individual circular cylinder and the corresponding change in drag, a simple three-component balance was used. The cylinder represents the platform legs. Two types of surface roughness were tested, first a plain wooden surface and then with a layer of coarse sand applied to the whole surface. It was seen that the rougher surface provoked an earlier transition to a turbulent boundary layer, causing an earlier drop in drag which is a better fit to estimated full-scale characteristics.Finally, the element that contributes most to the inaccuracy of the experiments is shown to be the difficulty of geometric similarity. Further investigation is needed.
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Finley, Ray Edward 1956. "DESIGN OF TUNNELS IN ROCK USING STRAIN ENERGY AND LIMIT STATE CONCEPTS." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275491.
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Neumann, Marcus A. "Le groupement méthyle-sonde de l'énergie potentielle." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10073.
Повний текст джерелаАнотація:
La dynamique de rotation de groupements methyle a basse temperature est utilisee pour sonder la surface d'energie potentielle dans differents cristaux moleculaires. Trois types d'observables caracterisent le potentiel de rotation : l'eclatement tunnel, les excitations de torsion et l'orientation du groupement methyle. La dynamique de rotation est etudiee experimentalement par la diffusion inelastique de neutrons et la spectroscopie raman. Des structures cristallines sont obtenues par diffraction de neutrons sur poudre. Le modele de la particule isolee presente une bonne approximation pour la description du mouvement quantique des groupements methyle. A partir des structures cristallines, les potentiels de rotation sont calcules par differentes methodes de calcul de l'energie potentielle, et les observables sont determinees par la solution numerique de l'equation de schrodinger. Le meilleur accord entre calcul et experience est obtenu par la methode de la fonctionnelle de densite. Des deviations du modele de la particule isolee sont expliquees par le couplage rotation-precession et le couplage entre rotateurs methyle. Des phenomenes de couplage sont etudies en detail dans la 4-methyle pyridine, le durene et un clathrate d'hoffman. Le couplage entre groupements methyle est pris en compte par la solution numerique de l'equation de schrodinger de plusieurs rotateurs methyle couples. Une section a part est consacree au transfert de protons dans l'acide benzoique.
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Rambaud, Christophe. "Etude, par spectroscopie optique, de la délocalisation quantique de protons dans des cristaux d'acide benzoi͏̈que." Grenoble 1, 1989. http://www.theses.fr/1989GRE10103.
Повний текст джерелаАнотація:
Les transitions optiques des molecules de thioindigo dopant des cristaux d'acide benzoique, sont sensibles au transfert des protons par effet tunnel le long des liaisons hydrogene intradimeres de la matrice. Mesure dans le cas d'un acide carboxylique des niveaux d'energie des protons delocalises et de l'element de matrice d'effet tunnel. Sensibilite du systeme a transfert de protons aux contraintes internes et externes. Deduction des vitesses de relaxation des protons delocalises, comparaison avec des calculs theoriques indiquant l'importance des processus a plusieurs phonons dans cette relaxation. Utilisation de l'effet d'un champ electrique pour influencer la delocalisation des protons
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Widell, Kristina Norne. "Energy efficiency of freezing tunnels : towards an optimal operation of compressors and air fans." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16431.
Повний текст джерелаАнотація:
Fish is one of Norway’s main exports, and can be shipped fresh, frozen or dried. This thesis examines the freezing of fish in batch tunnels and ways to increase the energy efficiency of this process. A fish freezing plant on the west coast of Norway was used as a baseline case and measurements were made of the freezing system. Different aspects of this system were simulated, mainly using MATLAB. The focus was on the compressors and the freezing tunnels of an industrial refrigeration system. The compressors and the freezing tunnel fans are the largest consumers of electricity, but they are often not operated at the highest efficiency. An analysis of the compressor operation showed that it was far from optimal, with several compressors often operating at part-load simultaneously. These were screw compressors regulated by slide valves, which provide easy capacity control, but also have low energy efficiency. The refrigeration system had several different sized compressors, and the results showed that it was possible to run the system with only one compressor at part-load operation. The total coefficient of performance was improved by as much as 29% for a low production period. A further analysis showed that installing a variable speed drive on one compressor would also improve energy efficiency and make capacity regulation straightforward. The freezing system included five batch freezing tunnels, each of which had a freezing capacity of more than 100 tonnes of pelagic fish. A typical freezing period lasted typically 20 h and decreased the fish temperature to -18◦C or below. The main task was to develop a computer program that could simulate the freezing process and the refrigeration system and locate opportunities for improvement. The air velocities inside the freezing tunnel varied with location, which were pinpointed using the computational fluid dynamics software program Airpak. These velocities were used in freezing time calculations. It was shown that a guide blade installed in the air flow at a critical location improved the air velocity distribution compared with no guide blade. Without the guide blade, the freezing times of the products were between 16 h and 32 h, but with a guide blade they were between 17h and 21 h, a span of only 4 h. These freezing times were calculated with a modified Plank’s equation. A numerical model was programmed in MATLAB and it was used to simulate the temperatures of the products. The model was a two-dimensional finite difference approximation of the heat conduction equation. The simulation results were compared to measured temperatures, to validate the model. The measured temperatures were also used for validation of another simulation program, programmed in Modelica. The final stage of this research involved testing different alternatives for reduced fan operation. The program for the product model was extended with models for calculating the energy consumption of the air fans and the compressors and using Airpak-simulated velocities. The air fan speed was reduced to 83%, 67%, 50% and 33% of full air fan speed. This was tested at 5 different points during the freezing period, to see how the freezing times were affected. Full air speed during the freezing period resulted in a total freezing time of 20 h. A reduction in air fan speed to 33% after 8 h resulted in an increase in total freezing time of 10 hours (47% longer) but reduced energy consumption to 73.8% of the baseline case. An alternative with only 4 h longer freezing time resulted in an energy consumption of 80.5% of the baseline case. It was assumed that the fans had variable speed drives. The effect of reduced air inlet temperature was also tested and the results show that this can reduce freezing times. The effect on the total energy consumption was not large and also depends on the rest of the refrigeration system. Issues raised by this thesis are relevant for future research. It is suggested that the main simulation program is expanded by incorporating more detailed models of the refrigeration system. Dynamic operation of the air fans is also a possibility, for example to gradually reduce fan speed with decreasing product heat load.
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Faure, Frédéric. "Approche géométrique de la limite semi-classique par les états cohérents et mécanique quantique sur le tore." Grenoble 1, 1993. http://www.theses.fr/1993GRE10188.
Повний текст джерелаАнотація:
Cette these est consacree a des problemes lies a l'etude de la limite semi-classique en mecanique quantique. Le premier chapitre presente une formulation geometrique qui est equivalente au principe variationnel. Elle consiste a concevoir la dynamique classique comme une projection orthogonale de la dynamique quantique sur la famille des etats coherents. L'angle de la projection nous renseigne sur la validite de l'approximation obtenue. Ces resultats sont illustres par un exemple numerique. Le deuxieme chapitre s'attache a la mecanique quantique sur le tore en tant qu'espace de phase, et en particulier a l'etude des degenerescences dans le spectre de modeles du type harper, ou harper pulse qui manifestent du chaos classique. Ce type de modeles trouve ses applications essentiellement en physique du solide, notamment pour l'effet hall quantique. Cette etude se fait d'une part a l'aide de l'indice de chern qui caracterise de facon topologique la localisation des fonctions d'ondes lorsque des conditions de periodicite sont changees, et d'autre part par la distribution de husimi permet de representer un etat quantique dans l'espace de phase. Nous discutons le role joue par les etats associes a une separatrice, par l'effet tunnel et par la nature chaotique de la dynamique
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Gonzalez, Campos Jose Alberto. "Design and Experimentation of Darrieus Vertical Axis Wind Turbines." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1594690510943748.
Повний текст джерела
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Vilela, Mauro Francisco. "Energie photovoltaïque solaire multispectrale : épitaxie de cellule GaAs de haute performance et de diode tunnel GaAs." Grenoble INPG, 1992. http://www.theses.fr/1992INPG0011.
Повний текст джерелаАнотація:
Ce travail s'insere dans le cadre general de la conversion photovoltaique multispectrale de l'energie solaire a tres haut rendement. Le projet implique quatre cellules elaborees a partir de materiaux semiconducteurs iii-v de differentes largeurs de bande interdite (gap) gaas; (al,ga)as; (ga,in)as; (ga,in)(p,as), chaque cellule pouvant etre ainsi adaptee a des bandes spectrales differentes du rayonnement solaire. Un rendement de l'ordre de 40% peut ainsi etre obtenu grace a la mise en serie optique de ces quatre cellules. La presente etude porte plus particulierement sur la cellule gaas, cur du projet quadrispectral du lpses. Une cellule avec un rendement am1 de 26% est obtenue par epitaxie en phase vapeur par pyrolyse d'organometalliques (epvom), une modification de la structure traditionnelle est aussi proposee. Des resultats de cellules gaas sur substrats de substitution (ge et si) sont donnes et une etude de la diode tunnel gaas a ete entreprise en vue d'augmenter la stabilite thermique du composant, l'application etant l'obtention d'un tandem monolithique gaas/(al,ga)as. Enfin, l'etude detaillee du comportement (diffusion, effet memoire) de trois dopants utilises en epvom (te, sn et zn) a ete effectuee
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Rasch, André. "Utvärdering av Ngenic Tune : Smart styrning av värmesystem i småhus." Thesis, Högskolan Dalarna, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:du-25524.
Повний текст джерелаАнотація:
In 2016, the global energy consumption was represented to 20 % by buildings, where energy use supplied heating, cooling, lightning and water heating. For the following years until 2040, global energy consumption is expected to grow 48 %, which in turn make demand for energy efficient measures. For the years of 2030 as well 2050, the EU-commission have set up climate goals to reduce global greenhouse gas emissions. Along with this were presented strategies for meeting future climate goals, where one strategy is about increasing overall energy efficiency, which includes buildings. One way of increasing building energy efficiency is through implementation of smart heating control, a cost-effective solution which through a retrofitting measure may reduce building energy consumption. For this paper, a smart thermostat named Ngenic Tune was implemented into a selection of single family houses in Borlänge district heating network. The purpose was to study improvements in thermal comfort and reduction of return temperature from domestic substations. Through a combined survey-interview study of Ngenic Tune users, the study revealed promising potentials for large scale implementation of the technology. The smart thermostat also showed tendency of lowering the return temperature.
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Qiu, Donghai. "Theoretical and experimental study of tuned nonlinear energy sink : application to passive vibration control." Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0029/document.
Повний текст джерелаАнотація:
: Les travaux présentés dans cette thèse traitent du contrôle de systèmes dynamiques soumis à des excitations harmoniques et transitoires en utilisant des absorbeurs de type Nonlinear Energy Sink (NES). Plusieurs aspects ont été développés : la conception et la réalisation d'un nouveau design pour le NES cubique, l'étude de la location et du transfert irréversible d'énergie sur un NES bistable et le développement d'un critère de conception pour un NES à Vibro-Impact (VI). Dans un premier temps, un critère de conception est proposé pour le NES à raideur cubique. Le design proposé est basé sur des ressorts coniques ou des ressorts à pas variable. Un mécanisme à raideur négative est aussi introduit pour supprimer la partie linéaire et avoir une raideur cubique pure. Dans un deuxième temps, le concept du NES est validé expérimentalement par des essais statiques et des essais dynamiques. Une analyse de sensibilité est aussi menée sur la longueur des ressorts précontraints, elle dénote parfois un état bistable de l'oscillateur. Ensuite, le NES bistable ainsi obtenu est étudié plus en détail. Ce type d'absorbeur s'avère être très robuste pour différents types d’excitation. Des études expérimentales sont aussi menées afin d'explorer le comportement dynamique. Enfin, un critère de conception est proposé pour le NES à Vibro-Impact. Des calculs analytiques détaillés sont proposés pour contrôler les vibrations sous différentes excitations. L'étude expérimentale montre une bonne cohérence avec les résultats théoriquesThe work presented in this thesis deals with the passive control of dynamics systems subjected to harmonic and transient excitations using a Nonlinear Energy Sink (NES). Several research aspects have been developed: design theory and experimental study of a novel NES, efficient Targeted Energy Transfer (TET) of bistable NES and design criteria for optimally tuned Vibro-Impact (VI) NES. Firstly, a design criterion intended to provide optimal nonlinear stiffness is proposed. Then a novel design of NES system yielding cubic stiffness with conical springs or variable pitch springs and negative stiffness mechanism is developed. Secondly, the experimental procedures for static and dynamic test are presented and applied to validate the concept of NES system. Then a sensitivity analysis is performed with respect to the pre-compressed length of springs. Thirdly, the optimal design of the above device with negative stiffness (termed as bistable NES) is studied. This type of NES is proved to work robustly for different types of excitation, and experimental study of semi-active control are explored. Finally, design criteria for optimally tuned VI NES are studied. Detailed analytical calculations of clearance to control the vibration under different excitations are proposed. A good correspondence between theoretical and experimental results is observed
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Hobbs, William Bradford. "Piezoelectric energy harvesting: vortex induced vibrations in plants, soap films, and arrays of cylinders." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33811.
Повний текст джерелаАнотація:
The goal of this project was to develop a wind generator that utilizes the collective oscillating motion of multiple piezoelectric devices. These devices would be an alternative to rotating turbine designs for low power generation, for use in applications such as remote power generation. A series of inexpensive devices were developed that harvested energy from vortex shedding, both as independent and cooperative devices. The behavior of single devices was studied, but more interestingly, the way that multiple devices arranged together can increase power output was studied. It was shown that individual devices could harvest more energy if they were placed as specific positions relative to the vortices shed by devices upstream. Through investigating the behavior of these devices, fundamental principles of the phenomenon of vortex induced vibrations were explored. Methods were developed to measure the amplitude and frequency of these vibrations in a wind tunnel, through high speed video and correlations that were found between oscillation and power output from the piezoelectric transducers. Similarly, vortex induced vibrations were explored in an approximation of a two dimensional system in a flowing soap film.
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Caceres, Huambo Baltazar Nicolas. "Simulação e otimização de um secador industrial de tunel para frutas." [s.n.], 2002. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256434.
Повний текст джерелаАнотація:
Orientador: Florencia Cecilia MenegalliTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-01T22:24:36Z (GMT). No. of bitstreams: 1 CaceresHuambo_BaltazarNicolas_D.pdf: 28723626 bytes, checksum: 03dc6196782a5dd6ded014989951adac (MD5) Previous issue date: 2002
Resumo: o objetivo do presente estudo foi desenvolver um modelo matemático para um secador industrial de túnel para fi'utas, simulá-Ia e otimizar sua operação considerando a qualidade do produto como restrição principal na formulação do problema de otimização. Os secadores operam em forma semi-contínua e têm carrinhos e bandejas. O período de cada ciclo é determinado fazendo cumprir as especificações da umidade inicial e final do produto, de forma que cada carrinho com um número determinado de bandejas com fruta úmida seja alimentado em ciclos ao túnel enquanto outro que atingiu a umidade final é retirado do outro extremo do túnel. As configurações consideradas no estudo foram concorrente e contracorrente. O modelo que foi desenvolvido a partir dos balanços simultâneos de calor e massa para a fase sólida e gasosa, tanto para as bandejas (carrinhos) quanto para o túnel, é simples e apropriado para efeitos de otimização onde o tempo computacional é muito importante. O modelo foi aplicado para simular a secagem de uva Itália usando dados experimentais da cinética de secagem, ajustando-se os parâmetros de acordo aos requerimentos das equações do modelo. Os códigos de simulação e otimização foram desenvolvidosem FORTRAN 90 de Microsoft Fortran PowerStation. A não linearidade das equações do modelo e da restrição de qualidade da fruta, representada pela degradação de ácido ascórbico, conduziram ao desenvolvimento de um algoritmo para a solução do problema de otimização cuja função objetivo foi minimizar o consumo de energia por unidade de sólido seco, tempo do ciclo e temperatura máxima atingida pela fruta. Os resultados mostram as condições de operação ótimas para um número fixo de carrinhos no túnel e indicam que a configuração contracorrente é mais eficiente quando se avalia os requerimentos de calor por kg de sólido seco para uma degradação de ácido ascórbico aproximadamente constante. Igualmente, que se reduz o consumo de energia em ambas configurações quando comparado aos valores simulados sem otimizar.
Abstract: The non linearity of the equations of the model and the quality of the fruit, represented by the ascorbic acid degradation, leaded to develop an algorithm for the solution of the optimization problem which objective function was to minimize the energy consumption, cycle time and maximum temperature achieved by the fruit. Results show the optimal operation conditions for a fixed number of trucks in the tunnel and indicate that countercurrent configuration is more efficient when heat requirements per kg of dry solids is evaluated for approximately constant ascorbic acid degradation. Furthermore, energy consumption for both configurations is reduced when compared to non optimized simulation results.
Doutorado
Doutor em Engenharia de Alimentos
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Pierre, Mathieu. "Transport mono-électronique et détection de dopants uniques dans des transistors silicium." Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00540644.
Повний текст джерелаАнотація:
Cette thèse présente une étude du transport électronique à basse température dans des transistors à effet de champ nanométriques en silicium sur isolant. Leur comportement électrique dépend notamment de la constitution des jonctions entre les réservoirs et le canal, qui est déterminée lors de la fabrication par l'utilisation d'espaceurs de part et d'autre de la grille. Cette différence de comportement est exacerbée à basse température. Dans des transistors très courts, de longueur de grille typique égale à 30 nm, compte tenu de la diffusion des dopants lors du recuit d'activation, il est possible d'obtenir sous la grille un unique donneur bien couplé aux deux réservoirs. Sa présence est révélée par de l'effet tunnel résonant à travers les niveaux d'énergie associés à ses orbitales, observé à basse température à des tensions de grille inférieures au seuil du transistor. L'estimation de l'énergie d'ionisation de ce donneur donne une valeur supérieure à la valeur attendue pour un donneur dans du silicium massif, ce qui est attribué à l'effet du confinement diélectrique du donneur. À l'inverse, il est possible de définir des résistances d'accès au canal suffisantes pour y confiner les électrons. Un transistor se comporte alors comme un transistor mono-électronique à basse température, dont l'îlot est situé sous la grille. Ce moyen de créer un transistor mono-électronique est étendu à des systèmes d'îlots couplés, en déposant plusieurs grilles entre la source et le drain. Plusieurs comportements sont obtenus selon l'écart entre les grilles et la longueur des espaceurs. Ces systèmes sont utilisés pour réaliser le transfert d'un électron unique.
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Bílek, Jan. "Aerospace - Futuristický kokpit moderního letounu." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2010. http://www.nusl.cz/ntk/nusl-237164.
Повний текст джерелаАнотація:
This work describes the visualization design of the flight related quantities in a cockpit of a modern light sport aircraft. It focuses on the utilization of the state of the art trends in flight data displays and introduces the innovative implementation of the aircraft's energy state smart clues that reduce pilots' workload. The initial part of the work presents a research into the flight, engine and navigation data presentation on analog instruments, followed by their illustrative depiction in glass cockpits. Within the framework of this thesis, Microsoft Flight Simulator has been used as a source of the flight related data. Final advances in the display design were introduced through the implementation of the synthetic vision system and a visualization of the virtual tunnel in the sky.
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Marian, Laurentiu. "The tuned mass damper inerter for passive vibration control and energy harvesting in dynamically excited structural systems." Thesis, City University London, 2016. http://openaccess.city.ac.uk/14884/.
Повний текст джерелаАнотація:
A novel passive vibration control configuration, namely the Tuned-Mass-Damper-Inerter (TMDI) is proposed in this work. The TMDI combines the “inerter”, a mechanical two-terminal flywheel device developing resisting forces proportional to the relative acceleration of its terminals, with the well-known and widely used in various passive vibration control applications Tuned-Mass-damper (TMD). Introduced as a generalization of the TMD, the TMDI takes advantage of the “mass amplification effect” of the inerter to achieve enhanced performance compared to the classical TMD. For linear harmonically excited primary systems, analytical closed-form expressions are derived for optimal TMDI design/tuning parameters using the well-established and widely applied for the case of the classical TMD semi-empirical fixed-point theory. It is shown that for the same attached mass the TMDI system is more effective than the classical TMD to suppress vibrations close to the natural frequency of the uncontrolled primary system, while it is more robust to de-tuning effects. Moreover, it is analytically shown that optimally designed TMDI outperforms the classical TMD in minimizing the displacement variance of undamped linear single-degree-of-freedom (SDOF) white-noise excited primary systems. For this particular case, optimal TMDI parameters are derived in closed-form as functions of the additional oscillating mass and the inerter constant. Furthermore, pertinent numerical data are furnished, derived by means of a numerical optimization procedure, for classically damped mechanical cascaded chain-like primary systems base excited by stationary colored noise. This exemplifies the effectiveness of the TMDI over the classical TMD to suppress the fundamental mode of vibration for linear MDOF structures. It is concluded that the incorporation of the inerter in the proposed TMDI configuration can either replace part of the TMD vibrating mass to achieve lightweight passive vibration control solutions, or improve the performance of the classical TMD for a given TMD mass. The TMDI is further applied for passive vibration control of seismically excited building structures. An input non-stationary stochastic process compatible with the elastic design spectrum of the European aseismic code provisions (EC8) is assumed. The effectiveness of the proposed TMDI configuration over the classical TMD is assessed by performing response history analyses for an ensemble of EC8 spectrum compatible field recorded strong ground motions. The optimally tuned TMDI solution achieves considerable reduction of the peak average top floor displacement and peak average top floor accelerations of the considered primary structures compared to the one achieved by the optimally designed classical TMD, assuming the same additional mass in both cases. Furthermore, the TMDI configuration achieves significant reduction in the maximum displacement of the additional oscillating mass. In this study, the primary structures are assumed to behave linearly in alignment with current trends in performance based requirements for minimally damaged structures protected by passive control devices. Furthermore, optimally designed TMDI is applied for vibration suppression and energy harvesting via an electromagnetic device which transforms the mechanical kinetic energy into electrical energy. Unlike the case of traditional energy harvesting enabled TMD systems, the amount of available energy to be harvested by the herein proposed TMDI-based harvester is leveraged by changing the intensity of the mass amplification effect of the inerter, through mechanical gearing, without changing the weight of the TMDI system. Therefore, the inclusion of the inerter adds a “degree of freedom” or a design parameter to the classical TMD-based harvesters allowing to control the trade-off between vibration suppression and energy harvesting in a more flexible manner. Overall, the herein reported numerical data and analytical work provide evidence that the TMDI offers a novel promising solution for passive vibration control and energy harvesting. Most importantly, it opens several new research paths involving numerical/parametric work, as well as, prototyping, experimental testing and field deployment.
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Oliveira, Mariana Schmidt de. "Análise de pás para aerogeradores de eixo horizontal aplicados à geração de microenergia." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/163768.
Повний текст джерелаАнотація:
A geração de energia elétrica por meio de aerogeradores de microporte vem ganhando espaço em várias partes do mundo; porém, estudos que descrevem e analisam este artefato, ainda são restritos se comparados a aerogeradores de médio e grande porte. Países como China e Estados Unidos, por exemplo, buscam cada vez mais estudar a microgeração de energia eólica, servindo como motivação para que exista maior número de estudos neste campo, também aqui no país. Neste sentido, a presente pesquisa apresenta análise de perfis NACA com diferentes ângulos de passo visando a microgeração de energia eólica. Para tanto realizou-se levantamento das velocidades de vento na parte superior de um prédio localizado no centro de Porto Alegre durante 5 dias e os perfis aerodinâmicos foram testados no programa computacional Q-Blade. Selecionou-se 3 perfis NACA (0012, 6409, 1412), 3 ângulos de passo (15º, 30° e 45º) e 5 velocidades de vento (de 1m/s à 5 m/s). Os modelos analisados foram obtidos através de impressão 3D. Foram então realizados ensaios aerodinâmicos utilizando o túnel de vento nos quais foram medidos o número de rotação por minuto (RPM), a velocidade de vento da partida da hélice, a tensão, corrente e a potência elétrica, geradas para diferentes configurações de ensaio. O trabalho contribui no sentido de auxiliar projetos que envolvam design e tecnologia que visem à melhoria da funcionalidade prática de microgeradores eólicos de eixo horizontal para as diversas aplicações possíveis. Os resultados apontam que o ângulo de passo de 45º apresenta os maiores índices de rotação, tensão, corrente e potência elétrica para todos os perfis NACA analisados, sendo o perfil NACA 0012 o de maior destaque em relação a esses mesmos parâmetros.Electric power generation by small scale wind turbines has been gaining space in several parts of the world, however, studies that describe and analyze this artefact, are still more restrict in comparison to medium and large scale wind turbines. Countries such as China and the United States, for example, are increasingly seek to study wind power microgeneration, working as a motivator in order to increase the number of studies in the field, even here in the country. In this matter, the present research presents an analysis of NACA profiles with different pitch angles seeking wind energy microgeneration. In order to do so, it was gathered the wind speed of the top portion of a building located in central Porto Alegre during 5 days and the aerodynamic profiles were tested in the computer program Q-Blade. 3 NACA profiles (0012, 6409, 1412), 3 pitch angles (15º, 30° e 45º) and 5 wind velocities (1m/s to 5 m/s) were selected. The analyzed models were obtained through 3D printing. Aerodynamical tests were performed using the Wind tunnel and were observed the number of rotation per minute (RPM), the wind speed start of the propeller, electric tension, current and power generated for different test configurations. The work contributes to assisting projects that involves design and technology aimed at improving the practical functionality of horizontal axis wind generators for the various possible applications. The results indicate that the 45º pitch angle presents the highest rates of rotation, electric tension, current and power for all the NACA profiles analyzed, with the NACA 0012 profile being the most prominent in relation to these same parameters.
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Salaya, Sánchez Germán Ignacio. "Estudio experimental de la estela de un aerogenerador de tres aspas." Tesis, Universidad de Chile, 2013. http://www.repositorio.uchile.cl/handle/2250/116011.
Повний текст джерелаАнотація:
Ingeniero Civil MecánicoLa creciente utilización de sistemas de generación de energía renovable ha provocado un aumento importante en la investigación y desarrollo de estas tecnologías. Particularmente, el campo de la generación mediante energía eólica es uno de los más importantes hoy en día. Un factor determinante en la capacidad de generación a través de energía eólica es la eficiencia de las turbinas. Es común en estas máquinas encontrar eficiencias en torno al 45\%, Entre los factores que determinan la eficiencia están los aspectos geométricos y aerodinámicos de la turbina, y la estela turbulenta generada por las palas y el rotor. Esta ultima en particular es determinante tanto en la eficiencia individual de aerogeneradores como en la eficiencia global en el caso de parcelas eólicas, debido a la interferencia entre distintas turbinas. Se sabe que la gran mayoría de las pérdidas de eficiencia de las turbinas eólicas se deben a turbulencias generadas por las palas del rotor, por lo que la minimización de estas es el objetivo principal de los diseñadores hoy en día. Estos aspectos motivaron este trabajo de título, en el cual estudiamos experimentalmente el funcionamiento de una turbina eólica al interior de un túnel de viento mediante anemometría de hilo caliente. Se diseñó y construyó un modelo a escala de un aerogenerador y se instaló dentro del túnel de viento del laboratorio LEAF-NL, de la Universidad de Chile Se midió la potencia de la turbina como función de la velocidad de flujo del túnel de viento en un rango de velocidades de flujo de entre 0.5 y 3 [m/s] (TSR o tip speed ratio de 1.1 a 5.3), lo que entrega como resultado la curva característica de los aerogeneradores (curva S). A través un sistema de posicionamiento motorizado en 2D se midió el campo de velocidades en distintos planos transversales de la estela. Para esto se utilizó un anemómetro de hilo caliente operado de manera síncrona con la posición angular instantánea del rotor de la turbina, con el objetivo de realizar una detección coherente de la velocidad en la estela con la posición angular del rotor. De esta manera se obtuvo el campo de velocidades medio y fluctuante asociado a la posición de las palas de aerogenerador. La medición sincronizada de los promedios temporales de velocidad permite identificar la influencia de cada de cada pala en la estela y además identificar la distribución de intensidad turbulenta. Finalmente se generaron mapas de velocidad en distintos planos de corte transversal a la estela, con lo que adicionalmente se logró evaluar la expansión de la estela y poder obtener un parámetro de razón de áreas, dicho parámetro permite calcular con éxito los coeficientes de potencia y empuje (Cp y Ct), los cuales coinciden con los valores reales medidos.
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Vasseur, Guillaume. "Étude par ARPES et STS des propriétés éléctroniques de réseaux métalliques et organiques nanostructurés." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0151/document.
Повний текст джерелаАнотація:
Dans ce travail nous démontrons, au travers de deux études, l'intérêt fondamental du couplage des techniques de photoémission résolue en angle (ARPES) et de spectroscopie tunnel (STS) dans l'analyse des propriétés électroniques d'interfaces nanostructurées. Dans la première partie, nous présentons une méthodologie permettant de déduire le potentiel de surface induit par la reconstruction triangulaire d'une monocouche d'Ag/Cu(111). Cette méthode est basée sur la mesure des gaps caractérisant la structure de bande de l'état de Shockley du système aux points de haute symétrie de la zone de Brillouin. L'évaporation d'adatomes de potassium permet d'augmenter le nombre de gaps accessibles en photoémission en décalant les bandes vers les états occupés. Dans un modèle d'électrons presque libres, leur amplitude nous donne accès aux premières composantes de Fourier du potentiel. La reconstruction de ce dernier dans l'espace direct nous permet ensuite de calculer la densité d'états locale que nous comparons aux mesures de conductance STS. La seconde partie est consacrée à l'étude de la croissance et des propriétés électroniques des molécules de 1,4-dibromobenzène (DBB) et 1,4-diiodobenzène (DIB) évaporées sur Cu(110). Leur dépôt à température ambiante sur la surface entraîne la déshalogénation des molécules et la formation de phases organométalliques. A 200°C, le système polymérise pour former des chaînes unidimensionnelles de poly(p-phénylène) parfaitement alignées. Les mesures ARPES révèlent l'existence d'une bande pi unidimensionnelle d'états HOMOs dispersant sous le niveau de Fermi. En STS, nous observons également, pour des petites chaînes, le confinement des états LUMOs dans la partie inoccupée du spectre. Le déconfinement de ces états pour les grandes chaînes conduit à la formation d'une bande continue croisant le niveau de Fermi, conférant au polymère un caractère métallique 1D. Le gap HOMO-LUMO est alors mesuré à 1.15 eVIn this work, through two different studies, we demonstrate the fundamental interest in the coupling of angle resolved photoemission (ARPES) and scanning tunneling spectroscopy (STS) to investigate the electronic properties of nanostructured interfaces. In the first part we present a methodology to determine the surface potential of the triangular reconstructed one monolayer of Ag/Cu(111) interface from ARPES. This method is based on the measurement of the Shockley state band structure’s gaps at the high symmetry points of the Brillouin zone. Deposition of potassium adatoms allows us to shift the surface state towards higher binding energies in order to increase the number of accessible gaps in photoemission. From the magnitude of these gaps we deduce the two first Fourier components of the potential felt by electrons using the nearly free electron model. Then we reconstruct it and calculate the local density of states in order to compare it with the conductance maps probed by STS. In the second part we report the study of the growth and the electronic properties of the two molecules 1,4-dibromobenzene (DBB) and 1,4-diiodobenzene (DIB) evaporated on Cu(110). For room temperature deposition, we first observe their deshalogenation and the formation of an intermediate organometallic phase. Then, above 200°C, the system polymerizes into a long-range ordered array of one dimensional poly(p-phenylene) polymer. ARPES intensity maps allowed us to identify a one dimensional graphene-like strongly dispersive pi-band below the Fermi energy. By STS we also observed LUMOs confined states for small chains over the Fermi level. The loss of confinement for long chains induces the formation of a continuous dispersive band which crosses the Fermi energy, conferring a 1D metallic character to the polymer. The HOMO-LUMO gap is found to be 1.15 eV