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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

Inkjet and Screen Printed Electrochemical Organic Electronics

Mannerbro, Richard, Ranlöf, Martin January 2007 (has links)
<p>Linköpings Universitet och Acreo AB i Norrköping bedriver ett forskningssamarbete rörande organisk elektrokemisk elektronik och det man kallar papperselektronik. Målet på Acreo är att kunna trycka denna typ av elektronik med snabba trycktekniker så som offset- eller flexotryck. Idag görs de flesta demonstratorer och prototyper, baserade på denna typ av elektrokemisk elektronik, med manuella och subtraktiva mönstringsmetoder. Det skulle vara intressant att hitta fler verktyg och automatiserade tekniker som kan underlätta detta arbete. Målet med detta examensarbete har varit att utvärdera vilken potential bläckstråleteknik respektive screentryck har som tillverkningsmetoder för organiska elektrokemiska elektroniksystem samt att jämföra de båda teknikernas för- och nackdelar. Vad gäller bläckstråletekniken, så ingick även i uppgiften att modifiera en bläckstråleskrivare avsedd för kontor/hemmabruk för att möjliggöra tryckning av de två grundläggande materialen inom organisk elektrokemisk elektronik - den konjugerade polymeren PEDOT och en elektrolyt.</p><p>I denna uppsats rapporteras om hur en procedur för produktion av elektrokemisk elektronik har utvecklats. Världens första elektrokemiska transistor som producerats helt med bläckstråleteknik presenteras tillsammans med fullt fungerande implementeringar i logiska kretsar. Karaktärisering av filmer, komponenter och kretsar som producerats med bläckstråle- och screentrycksteknik har legat till grund för den utvärdering och jämförelse som har gjorts av teknikerna. Resultaten ser lovande ut och kan motivera vidare utveckling av bläckstrålesystem för produktion av prototyper och mindre serier. En kombination av de båda nämnda teknikerna är också ett tänkbart alternativ för småskalig tillverkning.</p> / <p>Linköping University and the research institute Acreo AB in Norrköping are in collaboration conducting research on organic electrochemical electronic devices. Acreo is pushing the development of high-speed reel-to-reel printing of this type of electronics. Today, most demonstrators and prototypes are made using manual, subtractive patterning methods. More tools, simplifying this work, are of interest. The purpose of this thesis work was to evaluate the potential of both inkjet and screen printing as manufacturing tools of electrochemical devices and to conduct a comparative study of these two additive patterning technologies. The work on inkjet printing included the modification of a commercially available desktop inkjet printer in order to print the conjugated polymer PEDOT and an electrolyte solution - these are the two basic components of organic electrochemical devices. For screen printing, existing equipment at Acreo AB was employed for device production.</p><p>In this report the successful development of a simple system and procedure for the inkjet printing of organic electrochemical devices is described. The first all-inkjet printed electrochemical transistor (ECT) and fully functional implementations of these ECTs in printed electrochemical logical circuits are presented.</p><p>The characterization of inkjet and screen printed devices has, along with an evaluation of how suitable the two printing procedures are for prototype production, been the foundation of the comparison of the two printing technologies.</p><p>The results are promising and should encourage further effort to develop a more complete and easily controlled inkjet system for this application. At this stage of development, a combination of the two technologies seems like an efficient approach.</p>
252

Nanoindentation in situ a Transmission Electron Microscope

Johnson, Lars January 2007 (has links)
<p>The technique of Nanoindentation <em>in situ</em> Transmission Electron Microscope has been implemented on a Philips CM20. Indentations have been performed on Si and Sapphire (<em>α-Al</em><em>2</em><em>O</em><em>3</em>) cut from wafers; Cr/Sc multilayers and <em>Ti</em><em>3</em><em>SiC</em><em>2</em> thin films. Different sample geometries and preparation methods have been evaluated. Both conventional ion and Focused Ion Beam milling were used, with different ways of protecting the sample during milling. Observations were made of bending and fracture of samples, dislocation nucleation and dislocation movement. Basal slip was observed upon unloading in Sapphire. Dislocation movement constricted along the basal planes were observed in <em>Ti</em><em>3</em><em>SiC</em><em>2</em>. Post indentation electron microscopy revealed kink formation in <em>Ti</em><em>3</em><em>SiC</em><em>2</em> and layer rotation and slip across layers in Cr/Sc multilayer stacks. Limitations of the technique are presented and discussed.</p>
253

Evaluation of the radiation protection at the new radiotherapy treatment department at the University Hospital of Umeå

Andersson, Sara January 2010 (has links)
<p>At the University Hospital of Umeå, NUS, a new radiation treatment department is being built. The purpose of this master thesis is to evaluate the actual radiation protection outside three out of five treatment rooms in the building, including two Varian and one Siemens accelerator, and to verify that the radiation limits for the staff and the general public, stated by the Swedish Radiation Safety Authority, are obeyed.</p><p>The evaluation of the radiation protection shielding is made through measurements. The nominal photon beam energies 6 and 15 MV (dose rates up to 500 MU/min) can be used, which means that both photons and neutrons will contribute to the effective dose. For the photon measurements, two different GM counters have been used and for the neutron measurements a Neutron detector with a polyethylene moderator and a <sup>3</sup>He recoil proton counter tube was applied. The thesis also includes a literature study of the photon and neutron energy spectra outside the treatment rooms in order to check that the measurement equipments are suitable to use.</p><p>The measured doses of the radiation shielding are below the radiation limits per week and year but the measurements indicate too high values per hour, i.e. momentary dose rate, at the height of isocenter of the primary walls and at the gap under the door for all three accelerators. The rooms with the Varian accelerators also show too high values per hour at the secondary wall where the door is attached. However, the limiting value per hour is only a recommendation and no extra reinforcement in therefore required. Nevertheless, one should avoid placing a workplace, for example a writing desk, close to the secondary and primary walls.</p>
254

Optical measuring system using a camera and laser fan-out for narrow mounting on a miniaturized submarine

Berglund, Martin January 2009 (has links)
<p>The aim was to develop, manufacture and evaluate diffractive lenses, or diffractive optical elements (DOE), for use in correlation with a camera to add perspective in pictures. The application is a miniaturized submarine developed in order to perform distant exploration and analysis in harsh and narrow environments. The idea is to project a laser pattern upon the observed structure and thereby add geometrical information to pictures acquired with an onboard CMOS camera. The design of the DOE-structures was simulated using the optimal rotational angle method (ORA). A set of prototype DOEs were realized using a series of microelectromechanical system (MEMS) processes, including photolithography, deposition and deep reactive-ion etching (DRIE). The projected patterns produced by the manufactured DOEs were found to agree with the simulated patterns except for the case where the DOE feature size was too small for the available process technology to handle. A post-processing software solution was developed to extract information from the pictures, called Laser Camera Measurement (LCM). The software returns the x, y and z coordinate of each laser spot in a picture and provides the ability to measure a live video stream from the camera. The accuracy of the measurement is dependent of the distance to the object. Some of the patterns showed very promising results, giving a 3-D resolution of ~0.6 cm, in each dot, at a distance of 1 m from the camera. Lengths can be resolved up til 3 m distance from the submarine.</p> / <p>Tillämpningen finns i en miniatyriserad ubåt framtagen för utforskning och analys av svåråtkomliga och trånga håligheter. Målet var att designa, tillverka och utvärdera en diffraktiv lins (DOE) för användning tillsammans med en kamera för att skapa perspektiv i bilder. Idén var att projicera ett lasermönster på objektet och därmed lägga till geometrisk information till bilderna tagna med CMOS kameran. Utformningen av DOE-strukturerna simulerades med the optimal rotational angle method (ORA). En uppsättning av prototyp DOE-linser tillverkades med hjälp av en serie mikrostrukturteknikprocesser, bland annat fotolitografi, deponering och plasmaetsning. Mönster projicerade med de tillverkade DOE-linserna stämde väl överens med önskade mönster, med undantag för de DOEs där strukturstorleken underskred processens begränsningar. En programvara, kallad Laser Camera Measurement (LCM), utvecklades för att extrahera information från bilderna. Programvaran returnerar x, y, och z koordinaterna för varje laserpunkt i en bild och ger möjlighet att mäta i en kontinuerlig videoström från kameran.  Mätosäkerheten är beroende av avståndet till objektet. Vissa mönster gav mycket lovande resultat, med en 3-D upplösning på ~0.6 cm, i varje punkt, på ett avstånd av 1 m från kameran. Längder kan upplösas upp till 3 m från kameran där ett så kallat far-field uppstår.</p> / DADU
255

Schlieren imaging of microrocket jets

Lekholm, Ville January 2009 (has links)
<p>In this report, microrockets from the company NanoSpace were studied using schlieren imaging techniques. The rocket chips are manufactured using MEMS technology, which requires compromises regarding the shape of the nozzle. The rocket chips are 22x22x0.85 mm, manufactured from laminated silicon. The nozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit. A semi in-line schlieren apparatus was designed, set up, and aligned. A small vacuum chamber was constructed, and a series of tests was conducted in order to qualitatively evaluate the consequences of these compromises, and other performance issues. It was found that the existing 1 kW quartz-tungsten-halogen lamp was sufficient as a light source, standard photographic equipment served well as an imaging device, and a 400 mm, f/7.9 achromatic doublet as schlieren lens, resolved enough detail in the exhaust gas to perform the studies. At maximum magnification, the viewing area was 7 by 4.5 mm, captured at 14 Mpixel, or about 1.5 µm/pixel. Several different rocket chips were studied, with helium, nitrogen and xenon as propellant gases. Feed pressure ranged from 0.5 bar to 3.5 bar, and the rockets were studied at atmospheric pressure and in vacuum, and with and without heaters activated. Through these studies, verification and visualization of the basic functionality of the rockets were possible. At atmospheric pressure, slipping of the exhaust was observed, due to the severe overexpansion of the nozzle. In vacuum, the nozzle was underexpanded, and the flow was seen to be supersonic. There was a measurable change in the exhaust with the heaters activated. It was also shown that the method can be used to detect leaks, which makes it a valuable aid in quality control of the components.</p>
256

Control of marine current energy conversion system

Nyhlén, Erik January 2010 (has links)
<p>This thesis involves the development of a system for control of a marine current energy conversion system. The control system is developed on the principles of load control, i.e. it aims to control the rotational speed of the turbine by controlling the power extracted from the generator. The system operates by feedback of the generator DC-voltage and current as well as the speed of the water current passing through the turbine. An IGBT-transistor controlled by an AVR-microcontroller executes control of the generator and hence the turbine. A digitally implemented PID-controller serves as the fundamental automatic control regime. The control system can be operated from a PC-application connected to the microcontroller through a serial wire connection. From the graphical user interface ofthe PC-application the system operator can set the system control parameters and monitor the state of the generator and turbine. The control system can be set to keep the turbine operating at a desired tip speed ratio, rotational speed or generator voltage. Further, for purposes of indoor testing of the control system a separate system, a motor control system, was developed as a part of this thesis work. The purpose of the motor control system is to enable simulating the behavior of a turbine with a motor driving the generator instead of an actual turbine. The motor control system operates by control of an ACS800 variable frequency drive that is connected to the motor. The motor control system allows its operator to feed in data describing the variations in water speed over time as well as data describing how the simulated turbine's power coefficient depends on its tip speed ratio. From this data the motor control system continuously calculates the torque that should be put on the generator axis by the motor. Results from test runs of the system show that the performance of the system is good. The system responds quickly to changes in the control parameters. Also the system manages to keep the specified control parameter quite well even during rapid changes in the water speed.</p>
257

Communal Polyethylene Biogas Systems : Experiences from on-farm research in rural West Java

Stoddard, Isak January 2010 (has links)
<p>In Lembang, a farming community on western Java, family-sized, plug-flow, polyethylene biogas systems fed with cow dung, are being used as an integrated solution to issues related to energy, agriculture and waste management. Through simple, on-farm research and observation, a number of key problems have been addressed and improvements made to the design. Due to the large supply of cow dung in the area, and the potential to spread the benefits of the technology beyond the homes of dairy farmers, the feasibility of developing a communal, polyethylene biogas system for several households, has been investigated. Experiments on small model-digesters were combined with observations of full-scale biogas systems in use. Measurement equipment and techniques were constructed and developed, in order to measure biogas production and other relevant process parameters. Results indicate that a communal system can be an appropriate choice, but only under a certain set of circumstances.</p>
258

Electric Power Generation and Storage Using a High Voltage Approach

Bolund, Björn January 2006 (has links)
<p>Production and consumption of electricity have grown enormously during the last century. No mater what the primary source of energy is, almost all generation of electricity comes from conversion of a rotational movement in a generator. The aim of this thesis is to see how high voltage technology influence production and storage of electricity. Power flow in the generators used to convert mechanical movement to electric energy is analyzed using Poynting‘s vector. The impact of new generator technology for efficient extraction of hydroelectric power is shown. Simulation of a large permanent magnet turbo generator is presented. A flywheel storage system for electric vehicles utilizing high voltage technology is also presented. In pulsed power applications, a cheap method for intermediate storage of energy during milliseconds, which enables an inductive primary storage is presented and experimentally tested.</p>
259

Windows of Opportunities : The Glazed Area and its Impact on the Energy Balance of Buildings

Persson, Mari-Louise January 2006 (has links)
<p>The impact of window area on the energy balance of a building was investigated by simulations in DEROB-LTH. The glazed area was varied in three types of buildings with different types of glazing and for several climates.</p><p>One low energy house was compared to a less insulated house but identical in size and layout. Three different types of glazing were used; uncoated double glazing, double glazing with one low-e coated pane and triple glazing with two low-e coated panes. Climates with variations in solar radiation, mean temperature, altitude and latitude were chosen.</p><p>The results show that if energy efficient window alternatives are chosen the flexibility of choosing the glazed area and orientation is higher. Choosing a larger area facing south resulted in a higher heating demand for uncoated double glazing in the standard house. An increased area also resulted in an increased peak load for heating for all the simulated cases. Choosing the energy efficient glazing type gave a decrease in heating demand for increased south facing glazed area in the standard house. In the low energy house the difference in heating demand between different areas was smaller than for the standard house. </p><p>An office module with two types of switchable glazing and one solar control glazing unit was used in three different climates; Stockholm, Brussels and Rome. Larger window areas increase the cooling demand but if glazing types with lower solar transmittance are used, the difference in cooling demand between different window areas decreases. An extremely large window area, however, increases the peak load both for cooling and for heating and should therefore be avoided. Energy can be saved by using switchable windows instead of solar control or in particular standard glazing.</p>
260

Optical Studies of Periodic Microstructures in Polar Materials

Högström, Herman January 2006 (has links)
<p>The optical properties of matter are determined by the coupling of the incident electromagnetic radiation to oscillators within the material. The oscillators can be electrons, ions or molecules. Close to a resonance the dielectric function exhibits strong dispersion and may be negative. A negative dielectric function gives rise to a complex wave vector which is associated with no allowed states for photons, i.e. high extinction and bulk reflectance, as well as the possibility to support surface waves. </p><p>It is possible to manufacture a dielectric material that generates a complex wave vector. Such materials are called photonic crystals and they may exhibit a frequency range without allowed states for photons, i.e. an energy gap. A photonic crystal has a periodically varying dielectric function and the lattice constant is of the same order of magnitude as the wavelengths of the gap. </p><p>In this thesis, two optical phenomena causing a complex wave vector are combined. Polar materials, which have lattice resonance in the thermal infrared causing strong dispersion, are studied in combination with a periodic structure. The periodicity introduced is achieved using another material, but also by structuring of the polar material. One, two and three dimensional structures are considered. The polar materials used are silicon dioxide and silicon carbide. It is shown, both by calculations and experiments that the two optical phenomena can co-exist and interact, both constructively and destructively. A possible application for the combination of the two phenomena is discussed: Selective emittance in the thermal infrared. It is also shown that a polar material can be periodically structured by a focused ion beam in such way that it excites surface waves.</p>

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