95 research outputs found

    The dream of imitating our Sun: The hopes and prospects for unlimited energy

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    Master's thesis in Mathematics and physicsThis paper follows the historical development of the fusion research, with an ultimate goal to make a fusion power plant. Starting in the 1950`s, the different methods, setbacks and breakthroughs are explained. Fusion occurs in plasma, and initially the knowledge of hot plasma was limited. Several instabilities and other leakages of the plasma to the walls were early identified, leading to a greater task than first assumed. Reasons why the tokamak machine are the preferred setup amongst many possible ways of confining the hot plasma are given. Results from the greatest tokamaks yet, JET, TFTR and JT-60U, are outlined and discussed. The next step towards a fusion power plant is ITER, a bigger and more powerful machine that are being built in France. The specifications and objectives of ITER are given, together with a discussion on the scientific meaning of the expected results. At the end, an overview of different power plant designs will show how the future of fusion depends on what results ITER gives

    Addressing stability issues in mediated complex contract negotiations for constraint-based, non-monotonic utility spaces

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    Negotiating contracts with multiple interdependent issues may yield non- monotonic, highly uncorrelated preference spaces for the participating agents. These scenarios are specially challenging because the complexity of the agents’ utility functions makes traditional negotiation mechanisms not applicable. There is a number of recent research lines addressing complex negotiations in uncorrelated utility spaces. However, most of them focus on overcoming the problems imposed by the complexity of the scenario, without analyzing the potential consequences of the strategic behavior of the negotiating agents in the models they propose. Analyzing the dynamics of the negotiation process when agents with different strategies interact is necessary to apply these models to real, competitive environments. Specially problematic are high price of anarchy situations, which imply that individual rationality drives the agents towards strategies which yield low individual and social welfares. In scenarios involving highly uncorrelated utility spaces, “low social welfare” usually means that the negotiations fail, and therefore high price of anarchy situations should be avoided in the negotiation mechanisms. In our previous work, we proposed an auction-based negotiation model designed for negotiations about complex contracts when highly uncorrelated, constraint-based utility spaces are involved. This paper performs a strategy analysis of this model, revealing that the approach raises stability concerns, leading to situations with a high (or even infinite) price of anarchy. In addition, a set of techniques to solve this problem are proposed, and an experimental evaluation is performed to validate the adequacy of the proposed approaches to improve the strategic stability of the negotiation process. Finally, incentive-compatibility of the model is studied.Spain. Ministerio de Educación y Ciencia (grant TIN2008-06739-C04-04

    Neuroinformatics in Functional Neuroimaging

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    This Ph.D. thesis proposes methods for information retrieval in functional neuroimaging through automatic computerized authority identification, and searching and cleaning in a neuroscience database. Authorities are found through cocitation analysis of the citation pattern among scientific articles. Based on data from a single scientific journal it is shown that multivariate analyses are able to determine group structure that is interpretable as particular “known ” subgroups in functional neuroimaging. Methods for text analysis are suggested that use a combination of content and links, in the form of the terms in scientific documents and scientific citations, respectively. These included context sensitive author ranking and automatic labeling of axes and groups in connection with multivariate analyses of link data. Talairach foci from the BrainMap ℱ database are modeled with conditional probability density models useful for exploratory functional volumes modeling. A further application is shown with conditional outlier detection where abnormal entries in the BrainMap ℱ database are spotted using kernel density modeling and the redundancy between anatomical labels and spatial Talairach coordinates. This represents a combination of simple term and spatial modeling. The specific outliers that were found in the BrainMap ℱ database constituted among others: Entry errors, errors in the article and unusual terminology

    Microelectromechanical Systems and Devices

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    The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

    Vision 21: Interdisciplinary Science and Engineering in the Era of Cyberspace

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    The symposium Vision-21: Interdisciplinary Science and Engineering in the Era of Cyberspace was held at the NASA Lewis Research Center on March 30-31, 1993. The purpose of the symposium was to simulate interdisciplinary thinking in the sciences and technologies which will be required for exploration and development of space over the next thousand years. The keynote speakers were Hans Moravec, Vernor Vinge, Carol Stoker, and Myron Krueger. The proceedings consist of transcripts of the invited talks and the panel discussion by the invited speakers, summaries of workshop sessions, and contributed papers by the attendees

    An empirical examination of interdisciplinary collaboration within the practice of localisation and development of international software

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    Acceptance on international markets is an important selling proposition for software products and a key to new markets. The adaptation of software products for specific markets is called software localisation. Practitioner reports and research suggests that activities of developers and translators do not mesh seamlessly, leading to problems such as disproportionate cost, lack of quality, and delayed product release. Yet, there is little research on localisation as a comprehensive activity and its human factors. This thesis examines how software localisation is handled in practice, how the localisation process is integrated into development, and how software developers and localisers work individually and collaboratively on international software. The research aims to understand how localisation issues around the above-mentioned classifications of cost, quality and time issues are caused. Qualitative and quantitative data is gathered through semi-structured interviews and an online survey. The interviews focused on the individual experiences of localisation and development professionals in a range of relevant roles. The online survey measured cultural competence, attitude towards and self-efficacy in localisation, and properties of localisation projects. Interviews were conducted and analysed following Straussian Grounded Theory. The survey was statistically analysed to test a number of hypotheses regarding differences between localisers and developers, as well as relationships between project properties and software quality. Results suggest gaps in knowledge, procedure and motivation between developers and translators, as well as a lack of cross-disciplinary knowledge and coordination. Further, a grounded theory of interdisciplinary collaboration in software localisation explains how collaboration strategies and conflicts reciprocally affect each other and are affected by external influences. A number of statistically significant differences between developers and localisers and the relevance of certain project properties to localisation were confirmed. The findings give new insights into interdisciplinary issues in the development of international software and suggest new ways to handle interdisciplinary collaboration in general

    Development of analytical techniques for studies on dispersion of actinides in the environment and characterization of environmental radioactive particles

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    Radioactive particles from three locations were investigated for elemental composition, oxidation states of matrix elements, and origin. Instrumental techniques applied to the task were scanning electron microscopy, X-ray and gamma-ray spectrometry, secondary ion mass spectrometry, and synchrotron radiation based microanalytical techniques comprising X-ray fluorescence spectrometry, X-ray fluorescence tomography, and X-ray absorption near-edge structure spectroscopy. Uranium-containing low activity particles collected from Irish Sea sediments were characterized in terms of composition and distribution of matrix elements and the oxidation states of uranium. Indications of the origin were obtained from the intensity ratios and the presence of thorium, uranium, and plutonium. Uranium in the particles was found to exist mostly as U(IV). Studies on plutonium particles from Runit Island (Marshall Islands) soil indicated that the samples were weapon fuel fragments originating from two separate detonations: a safety test and a low-yield test. The plutonium in the particles was found to be of similar age. The distribution and oxidation states of uranium and plutonium in the matrix of weapon fuel particles from Thule (Greenland) sediments were investigated. The variations in intensity ratios observed with different techniques indicated more than one origin. Uranium in particle matrixes was mostly U(IV), but plutonium existed in some particles mainly as Pu(IV), and in others mainly as oxidized Pu(VI). The results demonstrated that the various techniques were effectively applied in the characterization of environmental radioactive particles. An on-line method was developed for separating americium from environmental samples. The procedure utilizes extraction chromatography to separate americium from light lanthanides, and cation exchange to concentrate americium before the final separation in an ion chromatography column. The separated radiochemically pure americium fraction is measured by alpha spectrometry. The method was tested with certified sediment and soil samples and found to be applicable for the analysis of environmental samples containing a wide range of Am-241 activity. Proceeding from the on-line method developed for americium, a method was also developed for separating plutonium and americium. Plutonium is reduced to Pu(III), and separated together with Am(III) throughout the procedure. Pu(III) and Am(III) are eluted from the ion chromatography column as anionic dipicolinate and oxalate complexes, respectively, and measured by alpha spectrometry.Huomattava osa ympÀristöön kulkeutuvasta radioaktiivisuudesta on liittyneenÀ hiukkasiin siten ettÀ suurin osa aktiivisuudesta on keskittynyt lukumÀÀrÀltÀÀn harvaan joukkoon suurikokoisia hiukkasia. Huolimatta siitÀ, ettÀ radioaktiivisia pÀÀstöjÀ tuottaneet onnettomuudet ovat varsin kartoitettuja, on radioaktiivisten hiukkasten kÀyttÀytymisessÀ luonnossa vielÀ paljon selvitettÀvÀÀ. TÀmÀn vuoksi radioaktiivisten hiukkasten analysointi ja karakterisointi ympÀristönÀytettÀ analysoitaessa on perusteltua. Erilaisten analyyttisten menetelmien kehittyminen sekÀ synkrotronisÀteilylÀhteiden lisÀÀntynyt kÀyttömahdollisuus ovat laajentaneet potentiaalia tutkia non-destruktiivisesti (rakennetta tuhoamatta) ympÀristössÀ esiintyviÀ radioaktiivisia hiukkasia. TÀmÀ edesauttaa tietÀmystÀ hiukkasten historiasta, nykytilasta, sekÀ fysikaalis-kemiallisesta kÀyttÀytymisestÀ ympÀristössÀ. Analysoitaessa plutoniumia ja americiumia sisÀltÀviÀ hiukkasia radiokemiallisesti on yleensÀ tarpeellista erottaa nÀmÀ alkuaineet toisistaan ennen niiden mittaamista. Uusien erotusmenetelmien kehittÀmisessÀ sovelletaan mm. kromatografisia menetelmiÀ, jolloin saavutetaan perinteisiin radiokemiallisiin menetelmiin verrattuna etuja kuten ajansÀÀstö, erotustehokkuuden paraneminen, ja automatisoinnin mahdollisuus. VÀitöstyössÀ havainnollistettiin non-destruktiivisten analyyttisten ja mikroanalyyttisten menetelmien menestyksekÀs kÀyttö ympÀristössÀ esiintyvien radioaktiivisten hiukkasten karakterisoinnissa. MenetelmÀt tuottivat informaatiota joka liittyy hiukkasten radioaktiivisuuteen, fysikaaliseen ja kemialliseen koostumukseen, isotooppisuhteisiin, ja rakenteen alkuaineiden hapetustiloihin. Saatujen tietojen avulla on mahdollista arvioida ominaisuuksia liittyen hiukkasten alkuperÀÀn ja niiden kÀyttÀytymiseen ympÀristössÀ. VÀitöstyö pitÀÀ myös sisÀllÀÀn kahden radiokemiallisen on-line -tyyppisen erotusmenetelmÀn kehittÀmisen. Toinen menetelmistÀ kehitettiin americiumin erottamiseen ja mittaamiseen ympÀristönÀytteestÀ. MenetelmÀ testattiin kÀyttÀen standardisoituja nÀytteitÀ, ja sen havaittiin soveltuvan hyvin eritasoisen americiumpitoisuuden omaaville nÀytteille. Toisessa menetelmÀssÀ erotettiin plutonium ja americium merkkiaineliuoksesta kÀyttÀen samoja kromatografisia on-line -ratkaisuja kuin americiumille kehitetyssÀ menetelmÀssÀ

    MODEL, FRAMEWORK, AND PLATFORM OF HEALTH PERSUASIVE SOCIAL NETWORK

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    Persuasive technology (PT) has the potential to support individuals to perform self-management and social support as a part of health behavior change. This has led a few researchers in the intersection of the areas of health behavior change and software engineering to apply behavior change and persuasion theories to software development practices, enabling them to create innovative design principles and development-evaluation frameworks. Unfortunately these are too general for designing and evaluating health PT. Therefore, this dissertation proposes a model, framework, and platform of PT specifically designed for health intervention. The model and framework inform what, why, and how conceptually the suggested and required health behavior change strategies should be transformed into system features; and the platform explains how technically the transformation should be done. The platform includes functional requirements and provides most of the basic and standard computer code to develop the system features of such PT. The model, framework, and platform were designed to work with various health behavior change programs. Nevertheless, in this dissertation, they support health behavior change for physical activity. As an implementation of and tool to evaluate the model, framework, and platform, a technology called Persuasive Social Network for Physical Activity (PersonA) is introduced. PersonA is a combination of automatic input of physical activity data, a smart phone, and social networking. Two systems (SocioPedometer and PAMS) as leverages of PersonA have been developed and evaluated. The model, framework, and platform were evaluated based on the results of SocioPedometer’s usability testing and 4-week trials (n=14) and on PAMS’s usability testing (n=5). The results suggest that the systems were usable and accessible and that users were satisfied and enjoyed using it. Additional evaluations to the model and framework were conducted with the main purpose of eliciting users’ preferences with respect to the characteristics and system features proposed in the model and framework. They rated most of the characteristics as extremely important (average 4.27 of a 5.00 maximum) and most of the system features as very important (average of 4.09). The platform allowed the two systems to be easily developed by customizing the data input and information presented

    Models and Analysis of Vocal Emissions for Biomedical Applications

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    The International Workshop on Models and Analysis of Vocal Emissions for Biomedical Applications (MAVEBA) came into being in 1999 from the particularly felt need of sharing know-how, objectives and results between areas that until then seemed quite distinct such as bioengineering, medicine and singing. MAVEBA deals with all aspects concerning the study of the human voice with applications ranging from the neonate to the adult and elderly. Over the years the initial issues have grown and spread also in other aspects of research such as occupational voice disorders, neurology, rehabilitation, image and video analysis. MAVEBA takes place every two years always in Firenze, Italy. This edition celebrates twenty years of uninterrupted and succesfully research in the field of voice analysis

    Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers

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    Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method
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