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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.
291

Investigation and growth of nickel coatings for electrical contact applications

Fawakhiri, Maria January 2009 (has links)
Nickel based coatings were deposited on copper substrates by two different sputtering techniques from a nickel alloy based target. The substrates used were commercially available copper based substrates for low duty electrical contacts. The coatings were analyzed and evaluated as copper diffusion barriers for electrical contact applications. In addition two types of commercially available electroplated nickel coatings (referred to as type A electroplated coatings and type B electroplated coatings) were characterized for comparison. The Technique I sputtered coatings were deposited using three different substrate bias voltages and two different working gas pressures. The Technique II coatings were deposited using two different substrate bias voltages and two different working gas pressures. All sputtered coatings were deposited at a temperature of 200° C. The quality of the barriers was investigated by analyzing their composition, microstructure, stress, mechanical properties , and surface roughness. The results show that sputtered coatings have polycrystalline structures while the two plated films had (200) orientation and (111) orientation. Both plated coatings contained impurities that originate from chemicals used in the plating baths. The surface of the sputtered coatings reflects the substrate surface, while the electroplated samples on the same substrate (type A coatings) show a smooth mirror like surface and the type B electroplated coatings show a rough surface. Technique II sputtered coatings showed the highest hardness in the amount of 13 GPa, followed by electroplated type A coatings with a hardness of about 9 GPa while the Technique I coatings showed hardness of 6-8 GPa. All sputtered coatings exhibited compressive stress while the electroplated type A coatings exhibited tensile stress of almost twice the magnitude. In this study it is shown that sputtered nickel based coatings sputtered nickel based coatings are a promising more environmental friendly alternative to electroplated nickel coatings.
292

Schlieren imaging of microrocket jets

Lekholm, Ville January 2009 (has links)
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.
293

Clinical evaluation of atlas based segmentation for radiotherapy of prostate tumours

Granberg, Christoffer January 2011 (has links)
Abstract   Background Semi-automated segmentation using deformable registration of atlases consisting of pre-segmented patient images can facilitate the tedious task of delineating structures and organs in patients subjected to radiotherapy planning. However, a generic atlas based on a single patient may not function well enough due to the anatomical variation between patients. Fusion of segmentation proposals from multiple atlases has the potential to provide a better segmentation due to a more complete representation of the anatomical variation. Purpose The main goal of the present study was to investigate potential operator timesavings from use of atlas-based segmentation compared to manual segmentation of patients with prostate cancer. It was also anticipated that, and evaluated if, the use of semi-automated segmentation workflows would reduce the operator dependent variations in delineation. Materials and Methods A commercial atlas-based segmentation software (VelocityAI from Nucletron AB) was used with several atlases of consistently, protocol based, delineated CT images to create multiple-atlas segmentation proposals through deformable registration. The atlas that was considered most representative was selected to construct single generic atlas segmentation proposals. For fusion of the multiple-atlas segmentations an in-house developed algorithm, which includes information of local registration success was used in a MATLAB-environment[1]. The algorithm used weighted distance map calculations where weights represent probabilities of improving the segmentation results. Based on results from Sjöberg and Ahnesjö the probabilities were estimated using the cross correlation image similarity measure evaluated over a region within a certain distance from the segmentation. 10 patients were included in the study. Each patient was delineated three times, (a) manually by the radiation oncologist, (b) with a generic single-atlas segmentation and (c) with a fusion of multiple-atlas segmentations. For the methods (b) and (c) the radiation oncologist corrected the proposed segmentations blindly without using the result from method (a) as reference. The total number of atlases used for case (c) was 15. The operator time spent by the radiation oncologist was recorded separately for each method. In addition a grading was used to score how helpful the segmentation proposals were for the delineations. The Dice Similarity Coefficient, the Hausdorff distance and the segmented volumes were used to evaluate the similarity between the delineated structures and organs. Results An average time reduction of 26% was found when the radiation oncologist corrected the multiple atlas-based segmentation proposals as compared to manual segmentations. Due to more accurate segmentations and more time saved, segmentation with fused multiple-atlases (c) was superior to the generic single-atlas (b) method, which showed a time reduction of 17%. Hints of an affected intra- and inter-operator variability were seen. Conclusions Atlas-based segmentation saves time for the radiation oncologist but the segmentation proposals always need editing to be approved for dose planning. The atlases, the fusion of these and the software implementation needs to be improved for optimal results and to extend the clinically usefulness.
294

Clinical evaluation of atlas-based segmentation for radiotherapy of head and neck tumours

Lundmark, Martin January 2011 (has links)
Background Semi-automated segmentation using deformable registration of atlases consisting of pre-segmented patient images can facilitate the tedious task of delineating structures and organs in patients subjected to radiotherapy planning. However, a generic atlas based on a single patient may not function well enough due to the anatomical variation between patients. Fusion of segmentation proposals from multiple atlases has the potential to provide a better segmentation due to a more complete representation of the anatomical variation. Purpose The main goal of the study was to investigate potential operator timesaving from editing of atlas-based segmentation compared to manual segmentation for head & neck cancer. Materials and Methods A commercial atlas-based segmentation software (VelocityAI from Nucletron AB) was used together with several expert generated and protocol-based atlases of delineated CT images to create multiple atlas segmentations through deformable registration. The atlas that was considered most universal was selected to construct single atlas segmentation proposals. For fusion of the multiple atlas segmentations an in-house developed algorithm, including information of local registration success was used in a MATLAB-environment1. The algorithm uses weighted distance map calculations where weights represent probabilities of improving the segmentation results. Based on previous results1 the probabilities were estimated using the cross correlation image similarity measure evaluated over a region within a certain distance from the segmentation. Ten patients were incorporated in the study. Each patient was delineated three times, (a) manually by the radiation oncologist, (b) with a single atlas segmentation and (c) with a fusion of multiple atlas segmentations. For the methods (b) and (c) the radiation oncologist corrected the proposed segmentations blindly without using the result from method (a) as reference. For case (c) a total number of 11 atlas segmentations were used. The time spent for segmenting or editing the segmentation proposals by the radiation oncologist was recorded separately for each method and each individual ROI. In addition a grading was used to score how helpful the candidate segmentation proposals were for the structure delineations. The Dice Similarity Coefficient, the Hausdorff distance and the volume were used to evaluate the similarity between the delineated structures. Results The results show a time reduction in the order of 40% when the radiation oncologist only has to correct the multiple atlas-based segmentation proposal compared to manual segmentation. When using single atlas the corresponding figure is 21%. Conclusions Using atlas-based segmentation can reduce the time needed for delineation in the head and neck area of patients admitted for radiotherapy. 1C. Sjöberg and A. Ahnesjö, Evaluation of atlas-based segmentation using probabilistic weighted distance maps, Manuscript, Uppsala University, 2011 / Bakgrund Atlasbaserad, semiautomatisk segmentering skulle kunna användas för att underlätta den för onkologen tidskrävande uppgiften med att manuellt segmentera strukturer och organ i patienter vid behandlingsplanering inför strålbehandling. Tidigare segmenterade atlaspatienter ger med hjälp av deformeringsalgoritmer segmenteringsförslag för strukturer i den aktuella patienten. Dessa kan sedan kontrolleras och editeras av onkologen med en tidsbesparing gentemot manuell segmentering som följd. En atlas som baserats på en enstaka individ (singelatlas) kan dock ha begränsningar när det gäller att täcka de anatomiska variationer som finns mellan olika patienter. Därför har metoder med fusionering av multipla segmenteringsförslag från en databas bestående av ett antal sedan tidigare segmenterade patienter (fusionerad multipelatlas) potential att ge ett bättre segmenteringsresultat. Syfte Huvudsyftet med arbetet var att undersöka de möjliga tidsbesparingar för onkologen som kan åstadkommas när editering av atlasbaserad segmentering används vid planering inför strålbehandling i huvud- och halsområdet istället för manuell segmentering Material och metoder En kommersiell, atlasbaserad segmenteringsprogramvara (VelocityAI från Nucletron AB) användes i studien. Genom att låta en erfaren onkolog segmentera ett antal CT-studier (11 st) enligt ett vedertaget protokoll skapades en databas av atlaser som sedan, via deformerbara registreringar, kunde generera lika många segmenteringsförslag för en nytillkommen patient. Den enskilda atlas som ansågs mest representativ valdes till att framställa segmenteringsförslaget för metoden med singelatlas. Till metoden med fusionerade multipla atlaser användes en lokalt utvecklad MATLAB-algoritm baserad på viktade    distansmappar. Vikterna representerar sannolikheten för förbättrat segmenteringsresultat och baseras på tidigare resultat1 där sannolikheterna bestämts utifrån en beräkning av likheterna mellan bilderna i ett visst område från den specifika segmenteringen. Tio patienter har inkluderats i studien. Varje patient segmenterades tre gånger, (a) manuellt, (b) med singelatlas och (c) med fusionerade multipla atlaser. För metoderna (b) och (c) editerades sedan segmenteringsförslagen av onkologen utan att denne fick använda resultatet från metod (a) som referens. För fallet med fusionerade multipla atlaser, (c), användes databasen med 11 atlaser. Tiden onkologen behövde för segmentering respektive editering av segmenteringsförslaget uppmättes i varje enskilt fall för jämförelse. Onkologen fick även göra en bedömning av hur hjälpsamt segmenteringsförslaget var i samband med editeringen. För utvärdering av resultaten användes Dice’s similaritetskoefficient, Hausdorff’s distansmått samt strukturernas volym. Resultat Resultaten visar på att en tidsbesparing i storleksordningen 40 % är rimlig när onkologen editerar förslag från fusioneringen av multipla atlassegmenteringar i jämförelse med manuell segmentering. Vid användning av singelatlas är motsvarande siffra 21 %. Slutsatser Användandet av atlasbaserad segmentering kan reducera tidsåtgången för segmentering av patienter inför strålbehandling i huvud-halsområdet. 1C. Sjöberg and A. Ahnesjö, Evaluation of atlas-based segmentation using probabilistic weighted distance maps, Manuscript, Uppsala University, 2011
295

VO2 films as active infrared shutters

Johansson, Daniel January 2006 (has links)
An active optical shutter for infrared light (3-5 μm) has been designed, exploiting the phase transition in thermochromic vanadium dioxide (VO2). A spin coating processing route for VO2 films has been adapted to manufacture reproducible depositions onto sapphire (Al2O3) substrates. The VO2 films have been characterized by X-ray powder diffraction (XRPD) and infrared spectroscopy (FTIR), showing 55 % transmittance in the open mode and 0.1 % in the closed mode. The VO2 film temperature determines the operating mode of the shutter, and a resistive circuit of gold was deposited on top of the film for heating purposes. Switching times from the open to the closed mode down to 15 ms have been measured. This work is a part of a comprehensive project at the Swedish Defence Research Agency (FOI), aiming to improve active components for protection against lasers. The shutter within this work is at this stage an early prototype, and needs further development and complementary systems such as a control unit to be implemented in an optical system.
296

Secure Text Communication for the Tiger XS

Hertz, David January 2006 (has links)
The option of communicating via SMS messages can be considered available in all GSM networks. It therefore constitutes a almost universally available method for mobile communication. The Tiger XS, a device for secure communication manufactured by Sectra, is equipped with an encrypted text message transmission system. As the text message service of this device is becoming increasingly popular and as options to connect the Tiger XS to computers or to a keyboard are being researched, the text message service is in need of upgrade. This thesis proposes amendments to the existing protocol structure. It thoroughly examines a number of options for source coding of small text messages and makes recommendations as to implementation of such features. It also suggests security enhancements and introduces a novel form of stegangraphy.
297

Inkjet and Screen Printed Electrochemical Organic Electronics

Mannerbro, Richard, Ranlöf, Martin January 2007 (has links)
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. 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. / 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. 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. 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. 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.
298

Control System for Electromagnetic Environmental Testing of Electronics with Reverberation Chamber

Olofsson, Erik, Jakobsson, Jonny January 2009 (has links)
A reverberation chamber is a highly conductive cavity in which it is possible to generatehigh electromagnetic elds that can be considered statistically homogeneous. Reverberationchambers have existed as a resource for electromagnetic compatibility (EMC) testing formore than 30 years. Working to promote international co-operation on standardization, severalorganizations have published various EMC standards. At Combitech AB in Linkopinghave a chamber that is commercially used for dierent types of measurements. To makethe chamber more attractive and versatile it is within their interest to get a system whichis compatible with the latest standards. The project aimed to develop a control system forthe reverberation chamber at Combitech and to equip it with functionality enabling it tomake measurements according to current EMC standards. Using the programming softwareAgilent VEE a program was developed to communicate with the supporting equipment andmanage test routines. Within the program software lies functionality directly associate withmode stirring and mode tuning procedures for standards DO-160F and MIL-STD. Duringmeasurements the program has abilities for skipping frequencies, pause/continue the currentsweep, executing preset events and adding commented markers to the plot window. Someother usable functionality implemented is project save/load, help section, directory selectionand data export abilities. The system holds functionality enabling measurements accordingto the standards in question, though future work will be needed to be able to carry througha proper and correct measurement routine.
299

Analys och modellering av magnetisk minsvepning för marina ändamål / Analysis and modelling of magnetic mine sweep for naval purposes

Lindin, Andreas January 2007 (has links)
<p>I detta examensarbete har en metod för att utvärdera magnetiska minsvep utvecklats. Som beräkningsmodell används en SAM, Självgående Akustisk-magnetisk Minsvepare utvecklad av Kockums AB, ThyssenKrupp Marine Systems. I arbetet skapas en magnetisk modell för en SAM som beskriver sambandet mellan det alstrade magnetfältet och de utställda strömmarna. Vidare analyseras två olika metoder, multipolutveckling i prolata sfäroidala koordinater samt en uppsättning av dipoler, för att skapa en koncis modell över den magnetiska signatur som skapas av ett fartyg. Denna modell kan sedan användas för att optimera strömutstyrningen så att det genererade magnetfältet på ett så bra sätt som möjligt efterliknar det givna fartyget. Arbetet avslutas med att ta fram utvärderingsalgoritmer för tre olika typer av magnetiska minor.</p> / <p>In this Master's dissertation, a method to evaluate magnetic mine sweep is developed. As a calculation model, a Self-propelled Acoustic Magnetic Mine Sweep (SAM), developed by Kockums AB, ThyssenKrupp Marine Systems, is used. A model that describes the generated magnetic flux density from a SAM as a function of the feed current is developed. Furthermore, two methods to model the magnetic signature from a ship are employed; multipole expansion in prolate spheroidal coordinates and an array of magnetic point dipoles. Using these models makes it possible to optimise the feed current so that the magnetic flux density from a SAM is as similar to the ship’s signature as possible. Finally, algorithms to evaluate a mine sweep with respect to three different types of naval mines are developed.</p>
300

Analys och modellering av magnetisk minsvepning för marina ändamål / Analysis and modelling of magnetic mine sweep for naval purposes

Lindin, Andreas January 2007 (has links)
I detta examensarbete har en metod för att utvärdera magnetiska minsvep utvecklats. Som beräkningsmodell används en SAM, Självgående Akustisk-magnetisk Minsvepare utvecklad av Kockums AB, ThyssenKrupp Marine Systems. I arbetet skapas en magnetisk modell för en SAM som beskriver sambandet mellan det alstrade magnetfältet och de utställda strömmarna. Vidare analyseras två olika metoder, multipolutveckling i prolata sfäroidala koordinater samt en uppsättning av dipoler, för att skapa en koncis modell över den magnetiska signatur som skapas av ett fartyg. Denna modell kan sedan användas för att optimera strömutstyrningen så att det genererade magnetfältet på ett så bra sätt som möjligt efterliknar det givna fartyget. Arbetet avslutas med att ta fram utvärderingsalgoritmer för tre olika typer av magnetiska minor. / In this Master's dissertation, a method to evaluate magnetic mine sweep is developed. As a calculation model, a Self-propelled Acoustic Magnetic Mine Sweep (SAM), developed by Kockums AB, ThyssenKrupp Marine Systems, is used. A model that describes the generated magnetic flux density from a SAM as a function of the feed current is developed. Furthermore, two methods to model the magnetic signature from a ship are employed; multipole expansion in prolate spheroidal coordinates and an array of magnetic point dipoles. Using these models makes it possible to optimise the feed current so that the magnetic flux density from a SAM is as similar to the ship’s signature as possible. Finally, algorithms to evaluate a mine sweep with respect to three different types of naval mines are developed.

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