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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.
281

Diagnosing L2 English Learners’ Listening comprehension abilities with Scripted and Unscripted Listening Texts

Carney, Nathaniel January 2018 (has links)
L2 listening research has moved toward a focus on understanding the process of listening. However, there are still few detailed studies of L2 listening that reveal learners’ comprehension processes when listening to scripted and unscripted listening texts. Studies in which such processing has been discussed have lacked detailed diagnoses of how bottom-up and top-down processing interactively affect listeners’ comprehension. This study was designed to show how listeners’ process and comprehend texts, with a focus on how their bottom-up and top-down processing either assist or impede their comprehension. In this study, a group of 30 L1 Japanese university English language learners’ listening abilities were diagnosed. The 30 participants were at three listening proficiency levels—high, mid, and low—based on TOEIC listening proficiency scores. The diagnostic procedure involved participants listening to two scripted and two unscripted listening texts and then reporting what they comprehended through three tasks—L1 oral recalls, L2 repetitions, and verbal reports. Other data was also collected in the study to relate the comprehension of listening texts to other important listening-related variables including listening proficiency, lexical knowledge, listening anxiety, study abroad experience, short-term phonological memory, and working memory. The main finding of the study was that miscomprehension of listening texts was invariably multi-causal, with a combination of both bottom-up and top-down factors leading to comprehension difficulty. Although not a new finding, the study offered more detail than current research about how bottom-up and top-down processing occur interactively. Regarding the overall difficulty of the listening texts, unscripted texts were more difficult to comprehend than scripted texts, and high-proficiency participants had fewer listening difficulties overall than mid- and low-proficiency participants. Quantitative and qualitative results revealed common processing difficulties among all participants due to L1-related phonological decoding issues (e.g., /l/ vs. /r/), connected speech, unknown lexis, and a lack of familiarity with unscripted speech hesitation phenomena (e.g., um, like). Qualitative transcript examples showed how top-down knowledge influenced misinterpretations of words and phrases interactively with bottom-up information, making inaccurate understandings of listening difficult to overcome. In addition to revealing participants’ difficulties and the severity of their comprehension difficulties, the diagnostic procedure showed common strengths—key words and phrases understood well by participants. High-frequency vocabulary and shorter utterances were both shown to be comprehended well. Finally, quantitative results in the study revealed relationships of participants’ listening comprehension with other important listening related variables. Listening proficiency and listening anxiety had strong relationships with listening comprehension of the listening texts. Working memory and short-term phonological memory had no relationship with listening text comprehension. Finally, study abroad experience showed a relationship with comprehension, but with many caveats, and listening vocabulary knowledge was not related with comprehension, but again, with numerous caveats to consider. Based on the results, theoretical and pedagogical implications were posed. Theoretical implications from the study relate to the understanding of four concerns in L2 listening research. Mainly, data in the study will aid researchers’ understanding of how L2 English listeners process speech interactively (i.e., with bottom-up and top-down information) for comprehension, how L2 English listeners experience connected speech, how L2 listeners deal with unknown lexis, and how L2 listeners experience difficulties with features of unscripted speech. Pedagogical implications of the study include the need for increased teacher and learner awareness of the complexity of L2 listening, the need to have learners to track their own listening development, and the need for teachers to expose learners to unscripted listening texts and make them familiar with features of unscripted speech. Finally, suggestions for further research are posed, including conducting diagnostics assessments of L2 listening with listeners of different L1s and with more varied proficiency levels, using different diagnostic procedures to examine L2 listening comprehension, and using more instruments to understand listening-related variables’ relationships with L2 listening comprehension. / Teaching & Learning
282

Malmö’s cultural sound zone: how city marketing compares to lived realities

Goodrich, Julie January 2024 (has links)
This thesis examines the marketing of Malmö’s kulturljudzon (cultural sound zone) in the context of recent neoliberal planning practices in the city, with a focus on how the experiences of do-it-yourself (DIY) cultural actors compare to the kulturljudzon’s promotion and how they navigate relationships with municipal and economic representatives. Culture’s heightened role in current urban planning processes globally has transformed how participants in the cultural scenes of cities experience their environments, making it necessary to understand the ways that this has occurred in Malmö. Two qualitative methods, a functional documentary analysis of public texts about the kulturljudzon and a thematic qualitative text analysis of interviews with cultural actors, a property owner, and municipal employees are utilized to explore the manner in which the kulturljudzon has been marketed, how this marketing compares and differs to perspectives found within Malmö’s music scene, and the lived realities of DIY musicians and organizers in connection to the kulturljudzon. The analysis has revealed that the kulturljudzon has been presented as being a result of collaborative, participatory, and bottom-up planning processes, at times where culture and business are said to have shared interests, and promoted as a means for the city to grow its attractiveness. Additionally, once interviews were incorporated, DIY cultural actors expressed their limitations in the kulturljudzon, such as the pressure to produce profit from their work, their difficulties in finding and keeping rental spaces, and the feeling that the municipality cared about the symbolism of the kulturljudzon and what it meant for the city’s economy more than the substance of the culture within it. Interviews with a property owner and municipal employees deepened this discussion by providing insight as to the roles that different types of values play in their decision-making, their relationships to culture and cultural actors, and their goals for the kulturljudzon, its surrounding neighborhood, and Malmö as a whole. The data revealed sharp differences in power and alignments of stakeholders in this area, with the municipality and property manager combining their interests more readily than either were able to align with the cultural actors interviewed. The results of this study have implications for future research that prioritizes perspectives from urban DIY music scene members and cultural actors in understanding urban transformations, as this research can highlight shortcomings and misguidedness in planning processes. Further, this study exemplifies a need for planning officials to educate themselves on DIY cultural practices if they wish to create truly informed and participatory policies that promote all levels of cultural production and expression in their cities.
283

Étude intracrânienne sur les mécanismes cérébraux permettant la reconnaissance d’objets

Bertrand, Josie-Anne 06 1900 (has links)
La reconnaissance d’objets est une tâche complexe au cours de laquelle le cerveau doit assembler de manière cohérente tous les éléments d’un objet accessible à l’œil afin de le reconnaître. La construction d’une représentation corticale de l’objet se fait selon un processus appelé « bottom-up », impliquant notamment les régions occipitales et temporales. Un mécanisme « top-down » au niveau des régions pariétales et frontales, facilite la reconnaissance en suggérant des identités potentielles de l’objet à reconnaître. Cependant, le mode de fonctionnement de ces mécanismes est peu connu. Plusieurs études ont démontré une activité gamma induite au moment de la perception cohérente de stimuli, lui conférant ainsi un rôle important dans la reconnaissance d’objets. Cependant, ces études ont utilisé des techniques d’enregistrement peu précises ainsi que des stimuli répétitifs. La première étude de cette thèse vise à décrire la dynamique spatio-temporelle de l’activité gamma induite à l’aide de l’électroencéphalographie intracrânienne, une technique qui possède des résolutions spatiales et temporelles des plus précises. Une tâche d’images fragmentées a été conçue dans le but de décrire l’activité gamma induite selon différents niveaux de reconnaissance, tout en évitant la répétition de stimuli déjà reconnus. Afin de mieux circonscrire les mécanismes « top-down », la tâche a été répétée après un délai de 24 heures. Les résultats démontrent une puissante activité gamma induite au moment de la reconnaissance dans les régions « bottom-up ». Quant aux mécanismes « top-down », l’activité était plus importante aux régions occipitopariétales. Après 24 heures, l’activité était davantage puissante aux régions frontales, suggérant une adaptation des procédés « top-down » selon les demandes de la tâche. Très peu d’études se sont intéressées au rythme alpha dans la reconnaissance d’objets, malgré qu’il soit bien reconnu pour son rôle dans l’attention, la mémoire et la communication des régions neuronales distantes. La seconde étude de cette thèse vise donc à décrire plus précisément l’implication du rythme alpha dans la reconnaissance d’objets en utilisant les techniques et tâches identiques à la première étude. Les analyses révèlent une puissante activité alpha se propageant des régions postérieures aux régions antérieures, non spécifique à la reconnaissance. Une synchronisation de la phase de l’alpha était, quant à elle, observable qu’au moment de la reconnaissance. Après 24 heures, un patron similaire était observable, mais l’amplitude de l’activité augmentait au niveau frontal et les synchronies de la phase étaient davantage distribuées. Le rythme alpha semble donc refléter des processus attentionnels et communicationnels dans la reconnaissance d’objets. En conclusion, cette thèse a permis de décrire avec précision la dynamique spatio-temporelle de l’activité gamma induite et du rythme alpha ainsi que d’en apprendre davantage sur les rôles potentiels que ces deux rythmes occupent dans la reconnaissance d’objets. / Recognizing objects is a complex task requiring the brain to assemble visual information in such a way that coherent perception can happen. Building a visual cerebral representation is done through a bottom-up process, involving mainly occipital and temporal areas. A top-down mechanism from parietal and frontal areas, is thought to facilitate recognition by taking into account expectations and generating possible candidates. However, the precise mechanisms by which all these processes are done are still unclear. Studies investigating induced gamma response were able to link this activity to coherent perception of objects, suggesting a significant role of this activity in object recognition. However, these studies used imprecise recording techniques and stimuli repetition. The first study of this thesis aimed at describing with more precision the induced gamma activity using intracranial encephalography and a fragmented images paradigm in which only new stimuli are presented. Moreover, the task was presented again 24 hours later to circumscribe top-down mechanisms. Results show that the induced gamma activity is highest at recognition in regions involved in bottom-up processes. Top-down mechanism involved occipito-parietal areas when images were presented for the first time. When images were presented again 24 hours later, frontal areas mediated top-down facilitation, suggesting that top-down mechanisms vary according to task demand. Alpha rhythm has been less clearly related to visual perception, but is nevertheless well known to be involved in attention, memory and long-distance brain communication. The second study of this thesis investigated the role of alpha rhythm in object recognition, using the same technique and task as in the first study. Time-frequency analysis revealed a strong alpha activity unspecific to recognition, which was propagating from posterior to anterior regions. Phase coherence analysis, however, showed significant phase synchronisation specific to recognition. A similar pattern of alpha activity was found 24 hours later. However, the activity was stronger in frontal regions and the phase synchronisation was more distributed. Alpha rhythm is thus thought to be involved in attentional and communicational mechanisms of object recognition. In conclusion, this thesis was able to describe the precise spatio-temporal dynamics of induced gamma and alpha activity and suggest potential roles of these rhythms in response to object recognition.
284

Estratégia atencional para busca visual e reconhecimento invariante de objetos baseada na integração de características bottom-up e top-down / Attentional strategy for visual search and invariant object recognition based on bottom-up and top-down feature integration

Neves, Evelina Maria de Almeida 30 June 2000 (has links)
Uma das tarefas básicas dos mecanismos atencionais é decidir qual a localização dentro do campo visual, em que devemos prestar atenção primeiro. Um objeto que contenha características distintas, tais como orientação, forma, cor, tamanho, brilho, textura, etc. diferentes, pode atrair a atenção de uma maneira \"bottom-up\". A informação \"top-down\" baseia-se no conhecimento prévio e tem uma grande influência nas localizações atendidas. Inspirado nos mecanismos da Atenção Visual Humana, embora sem a pretensão de simulá-la, este trabalho prevê o desenvolvimento de uma nova metodologia que integra os dois tipos de informações: \"bottom-up\" e \"top-down\". Características \"bottom-up\" são geradas a partir de Momentos e essas informações são utilizadas em mapas de saliência, enquanto que um conhecimento prévio é utilizado para gerar pistas \"top-down\". Neste trabalho, desenvolveu-se uma metodologia específica para a busca e o reconhecimento visual em cenas com múltiplos objetos, utilizando para isso uma rede \"fuzzy\" contendo três subsistemas \"fuzzy\". Dada uma imagem de entrada, o objetivo consiste em se detectar regiões que possam conter informações mais significativas, a fim de que se possa guiar e restringir processamentos mais complexos. A inclusão de mecanismos de atenção (seleção de uma região de interesse dentro da imagem) é de fundamental importância pois os resultados obtidos pelo método podem ser usados para controlar a aquisição da imagem de uma maneira dinâmica. O modelo proposto está estruturado em três estágios principais: O primeiro estágio consiste em se segmentar os objetos e extrair características globais dos mesmos baseadas principalmente na teoria dos momentos, tais como tamanho, orientação, formato e distância e também média de nível de cinza. Por intermédio da comparação de um objeto com os outros presentes na cena, características \"bottom-up\" de conspicuidade são usadas para guiar a atenção ao objeto mais diferente. Por intermédio do uso da lógica \"fuzzy\" é possível inferir com grande flexibilidade algumas regras de decisão baseadas nos princípios de percepção visual tais como as leis Gestalt. O segundo estágio consiste de um subsistema \"fuzzy top-down\" que combina diferentes características de acordo com a relevância das mesmas em diferentes tarefas. Finalmente, o terceiro estágio consiste de um subsistema \"fuzzy\" que integra as informações obtidas dos subsistemas anteriores e fornece um índice geral de saliência, e indica a provável localização do objeto a ser reconhecido. A nova abordagem foi testada com objetos geométricos levando-se em consideração as características que atraem a atenção dos serem humanos / One of the basic tasks assigned to the human attentional mechanisms is to decide which location in the visual field we must pay attention first. An object containing distinctive features (such as different orientation, shape, color, size, shine, texture, etc.) can attract attention in a bottom-up way. Top-down information is based on the previous knowledge and has a large influence on the attended locations. Inspired on human visual attention mechanisms, although it doesn\'t want simulate it, this work presents a new methodology to integrate two different kind of information: bottom-up and top-down. Bottom-up features are obtained from Moment Theory and this information is used in salience maps, while a previous knowledge is used to create top-down hints. In this work, an specific methodology to visual search and recognition was developed to be applied to scenes containing multiple objects by a fuzzy net with three fuzzy subsystems. The aim of this methodology is to detect regions that may contain the most significant information, in order to guide and to restrict most complex processing. The inclusion of attentional mechanisms (the selection of a region of interest in the image) is fundamental and can be used to control the image acquisition in a dynamic way. The proposed model is structured in three main stages. The first stage segments the objects and extracts global features of them, based on the Moment Theory such as size, orientation, shape and distance and gray level average. By comparing one object with the other ones present in the scene, bottom-up features of conspicuity are used to guide the attention to the most different object. The Fuzzy Logic allows us to infer with great flexibility some of decision rules based on the visual perception principles such as the Gestalt Laws. The second stage is a top-down fuzzy subsystem that combines different features according to the relevance of them in different tasks. Finally, the third stage is a fuzzy subsystem that integrates the information obtained from the previous sub-systems and gives us a general salience index. The new methodology was tested in geometrical objects considering the feature that attracts attention to human beings
285

"Det är inte bara folkvalda politiker som utövar offentlig makt" : En jämförande studie gällande främjande av integration i fem kommuner i Stockholms län / "It is not just elected representatives that exercise public power" : A comparative study of integration in five municipalities in Stockholm County

Degard, Emelie, Abdulla, Maya January 2009 (has links)
<p>Based on different integration policies, we aim to examine how five municipalities in Stockholm County are working to promote integration at a local level with focus on voter participation and to some extent, representativeness among foreign-born. Statistics provided by SCB shows that foreign-born tends to vote to a lesser extent than those born in Sweden. Further, we aim to examine the implementation of two policy documents established at a national level concerning integration in contrast to policy documents established at a local level in each different municipality. Further, we aim to examine summaries of actions taken in response to the local integration programs, as well as personal interviews. Each municipality will be considered separately, but we thus seek to make a comparative study. The study will be based on a qualitative approach. The implementation process of both central and local policy decisions concerning the promotion of integration will also be discussed in terms of two existing theories of implementation, based on two different perspectives. The result shows that interaction between different participants, such as local officials and politicians, is of importance for the implementation process. All of the studied municipalities have taken some actions in order to implement their goals concerning integration.</p>
286

Το μοντέλο των σκληρών και μαλακών οξέων και βάσεων ως εργαλείο στη χημεία των μοριακών ετερομεταλλικών μαγνητών / The principle of hard and soft acids and bases as a tool in the chemistry of molecular heterometallic magnets

Λαδά, Ζωή 09 October 2014 (has links)
Τα ομομεταλικά σύμπλοκα που περιέχουν αποκλειστικά 3d μεταλλοϊόντα, καθώς και τα ετερομεταλλικά σύμπλοκα 3d/4f μεταλλοϊόντων αποτελούν σήμερα πόλο έλξης για τους ανόργανους χημικούς, λόγω των σημαντικών μαγνητικών, οπτικών και καταλυτικών τους ιδιοτήτων. Η χημεία των πολυπυρηνικών συμπλόκων (πλειάδων) των μετάλλων μετάπτωσης της 1ης Σειράς αποτελεί σήμερα ερευνητικό πεδίο αιχμής, καθώς προκύπτει από την αλληλοεπικάλυψη των επιστημών της Χημείας, της Βιολογίας και της Φυσικής, βρίσκοντας εφαρμογές σε τομείς όπως η Βιοανόργανη Χημεία, η Χημεία των Μοριακών Υλικών και η Νανοτεχνολογία. Ιδιαίτερο ενδιαφέρον παρουσιάζουν οι μαγνητικές ιδιότητες των μοριακών πλειάδων μετά την ανακάλυψη του φαινομένου του Μονομοριακού Μαγνητισμού. Μαγνήτες Μοναδικού Μορίου, ΜΜΜ (Single Molecule Magnets, SMMs) είναι μοριακές πλειάδες οι οποίες μπορούν να διατηρούν το μαγνητικό προσανατολισμό τους, απουσία ενός μαγνητικού πεδίου, κάτω από μια συγκεκριμένη θερμοκρασία. Οι ΜΜΜ αντιπροσωπεύουν τη μικρότερη συσκευή αποθήκευσης πληροφοριών με ποικιλία δυνητικών εφαρμογών. Πολλοί ΜΜΜ των 3d μετάλλων έχουν υψηλό ολικό σπιν στη θεμελιώδη κατάσταση, αλλά υστερούν σημαντικά στο θέμα της μαγνητικής ανισοτροπίας, όπως αυτή αντικατοπτρίζεται στη μικρή τιμή της παραμέτρου σχάσης μηδενικού πεδίου D. Τα λανθανίδια διαδραματίζουν έναν ιδιαίτερο ρόλο στο Μαγνητισμό, εξαιτίας της μεγάλης μαγνητικής ροπής τους, και στις περισσότερες των περιπτώσεων, λόγω της τεράστιας μαγνητικής τους ανισοτροπίας. Στην τρισθενή τους όμως οξειδωτική κατάσταση, που είναι και η πιο σταθερή, παρουσιάζουν το μειονέκτημα της πολύ ασθενούς αλληλεπίδρασης ανταλλαγής μεταξύ των μεταλλοϊόντων, ως αποτέλεσμα της αποτελεσματικής προάσπισης των ασυζεύκτων ηλεκτρονίων των 4f τροχιακών. Το γεγονός αυτό οδήγησε στη διερεύνηση συστημάτων που συνδυάζουν 4f ιόντα με άλλα παραμαγνητικά είδη, όπως οργανικές ρίζες ή 3d ιόντα. Έτσι, η ταυτόχρονη ύπαρξη των τρισθενών λανθανιδίων (LnIII) και 3d μεταλλοϊόντων μπορεί να βελτιώσει το Μονομοριακό Μαγνητισμό των πλειάδων ένταξης οδηγώντας σε μαγνητικές ιδιότητες διαφορετικές από αυτές των 3d πλειάδων. Η Διπλωματική Εργασία μας στα πλαίσια του Μεταπτυχιακού Διπλώματος Ειδίκευσης «Αναλυτική Χημεία και Νανοτεχνολογία» αφορά τη χημεία των πλειάδων των 3d/4f- μεταλλοϊόντων. Στις προσπάθειές μας να συνθέσουμε ετερομεταλλικές πλειάδες Co ή Cu/LnΙΙΙ με υποκαταστάτες οξίμες (2-πυρίδυλο οξίμες, 2,4-πεντανιοδιόνη διοξίμη) και τη δι-2-πυρίδυλο κετόνη και τα παράγωγά της, απομονώσαμε και χαρακτηρίσαμε οικογένειες συμπλόκων μεταβάλλοντας κάθε φορά παραμέτρους της αντίδρασης, όπως τη φύση του οργανικού υποκαταστάτη, τον διαλύτη της αντίδρασης, την πηγή των μεταλλοϊόντων, τη θερμοκρασία, την πίεση, κ.α. Ως συνθετική πορεία χρησιμοποιήσαμε την “bottom-up” προσέγγιση. Η στρατηγική “bottom-up” χρησιμοποιεί τις χημικές ιδιότητες των διακριτών μορίων για να προκαλέσει: Α) Αυτο-οργάνωση ή αυτο-συναρμολόγηση σε μια χρήσιμη διαμόρφωση. Β) Οργάνωση σε συγκεκριμένη θέση. Η στρατηγική αυτή χρησιμοποιείται για τις έννοιες της μοριακής αυτο-οργάνωσης ή/και της μοριακής αναγνώρισης. Σε ευρύτερο επίπεδο, δηλαδή η “bottom-up” τεχνική δυνητικά μπορεί να παράγει παράλληλες συσκευές με πολύ φθηνότερους τρόπους σε σχέση με την “top-down” μέθοδο που χρησιμοποιείται ευρέως στη σύνθεση τεχνολογικού ενδιαφέροντος συσκευών. Η μοριακή αυτή προσέγγιση ξεκινά με χρήση πηγών ανεξάρτητων ατόμων ή μικρών μορίων για τη σύνθεση μεγάλων μοριακών νανοδομών με επιθυμητές και στοχευμένες ιδιότητες, με αποτέλεσμα να αναπτύσσεται το πεδίο της Ναντεχνολογίας. Δύο γενικές προσεγγίσεις για τη σύνθεση συμπλόκων Co ή Cu/LnIII είναι: η στρατηγική που βασίζεται στη χρησιμοποίηση «μεταλλικών συμπλόκων ως υποκαταστατών» και η στρατηγική που βασίζεται στην «απλή ανάμιξη των συστατικών». Στην παρούσα Διπλωματική Εργασία εφαρμόζεται η δεύτερη κατά σειρά προσέγγιση για την παρασκευή των παρακάτω συμπλόκων ενώσεων: [CoIII {(py)C(Η)NO}2{(py)C(Η)NOH}](ClO4) [CoIII2DyIII{(py)C(Η)NO}6(H2O)(DMF)](ClO4)3.3.2H2O [CoIII2GdIII{(py)C(Η)NO}6(H2O)(DMF)](ClO4)3.3.2H2O [CoIII2DyIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIII2GdIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIII2SmIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIII2TbIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIIIDyIII{(py)C(Ph)NO}3(NO3)3] [CoIIIEuIII{(py)C(Ph)NO}3(NO3)3] [CoIIISmIII{(py)C(Ph)NO}3(NO3)3].0.3MeOH [CoIIITbIII{(py)C(Ph)NO}3(NO3)3].0.3MeOH [CoIIIGdIII{(py)C(Ph)NO}3(NO3)3].0.3MeOH [CoIII2Na{(py)C(Η)NO}6].(OMe) [CoIII2DyIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2GdIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2TbIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2PrIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2YIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [Cu2(diba)4(κινοξαλίνη)]n [Cu3Dy2{(py)2CO2}{(py)2CO(OMe)}3{(py)2CO(OEt)}(NO3)4(H2O)2](ClO4)(OH) [Cu6{(py)2CO(OMe)}6(NO3)2](ClO4)4 [Cu3{(py)2C(OMe)(OH)}2{(py)2C(OMe)O}2(ClO4)2] (ClO4)2 .2MeOH [Cu{(py)2C(OH){CH2COCH3)}2](NO3)2.2H2O Οι δομές των συμπλόκων προσδιορίσθηκαν με Κρυσταλλογραφία Ακτίνων Χ Μονοκρυστάλλου. Σε επιλεγμένα σύμπλοκα από αυτά που συνθέσαμε μελετώνται οι μαγνητικές τους ιδιότητες. Τα σύμπλοκα χαρακτηρίστηκαν με φυσικές και φασματοσκοπικές τεχνικές. Τα δεδομένα μελετήθηκαν σε σχέση με τις γνωστές δομές των συμπλόκων και των τρόπων ένταξης των υποκαταστατών. / Homometallic complexes which contain exclusively 3d metal ions and heterometallic complexes with 3d/4f metal ions attract, nowdays, the intense interest of inorganic chemists, due to their important magnetic, optical and catalytical properties. The chemistry of polynuclear complexes (clusters) of the 1st row transition metals is a cutting-edge research area, since combines the sciences of Chemistry, Biology and Physics with applications in the fields of Bioinorganic Chemistry, Chemistry of Molecular Materials and Nanotechnology. After the discovery of the phenomenon of Single Molecule Magntesism, the magnetic properties of molecular clusters are a growning research field. Single Molecule Magnets (SMMs) are molecular clusters which can retain their magnetic orientation, in the absence of a magnetic field, below a certain temperature. SMMs represent the smallest information storage devices with multiple potential applications. Many SMMs of 3d metals exhibit high total spin in the ground state, but their disadvantage is the low value of Zero Field Splitting (ZFS) parameter, D. Lanthanides play an important role in Magnetism, due to their large spin and in most cases huge magnetic anisotropy. In their trivalent oxidation state, which is the most stable, they have the disadvantage of the very weak exchange interactions between the metal ions, as a result of the efficient shielding of unpaired 4f electrons. This fact has led to the investigation of systems combining 4f-metal ions with other paramagnetic species, such as organic radicals or 3d-metal ions. Thus, the simultaneous presence of trivalent lanthanides (LnIII) and 3d metal ions can improve the Single Molecule Magnetism behavior of coordination clusters leading to magnetic properties different from those of 3d clusters. Our Diploma Work in the context of the M.Sc. in “Analytical Chemistry and Nanotechnology” concerns the chemistry of 3d/4f clusters. In our efforts to synthesize heterometallic clusters of Co or Cu/LnIII with oximes (2-pyridyl oximes, 2,4-pentanedione dioxime) and di-2-pyridyl ketone as ligands, we have isolated and characterized new families of complexes, studying various reaction parameters, such as the nature of the organic ligand, the solvent of the reaction, the source of the metal ions, the temperature, the pressure etc. As synthetic route, we have used the “bottom-up” approach. The “bottom-up” approach uses the chemical properties of discrete molecules in order to cause: a) Self-organization or Self-assembly in an interesting configuration. b) Assembly with a specific stereochemistry. This strategy is used for the concepts of molecular self-organization and/or molecular recognition. Hence in a broader sense, the “bottom-up” approach can produce potential applications in devices with cheaper ways in relation to the “top-down” approach which is used widely for the synthesis of devices with technological interest. This molecular approach begins with the use of independent sources of atoms or small molecules for the synthesis of large molecular nanostructures with preferential and targeted properties, developing though the field of Nanotechnology. Two general synthetic approaches for the synthesis of Co or Cu/LnIII complexes are: the strategy which is based on the use of “metal complexes as ligands” and the strategy based on the “simple mixing of components”. In this Diploma Work we have used the second approach for the synthesis of the below mentioned complexes: [CoIII {(py)C(Η)NO}2{(py)C(Η)NOH}](ClO4) [CoIII2DyIII{(py)C(Η)NO}6(H2O)(DMF)](ClO4)3.3.2H2O [CoIII2GdIII{(py)C(Η)NO}6(H2O)(DMF)](ClO4)3.3.2H2O [CoIII2DyIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIII2GdIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIII2SmIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIII2TbIII{(py)C(Η)NO}6(H2O)(MeOH)](ClO4)3.3.2H2O [CoIIIDyIII{(py)C(Ph)NO}3(NO3)3] [CoIIIEuIII{(py)C(Ph)NO}3(NO3)3] [CoIIISmIII{(py)C(Ph)NO}3(NO3)3].0.3MeOH [CoIIITbIII{(py)C(Ph)NO}3(NO3)3].0.3MeOH [CoIIIGdIII{(py)C(Ph)NO}3(NO3)3].0.3MeOH [CoIII2Na{(py)C(Η)NO}6].(OMe) [CoIII2DyIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2GdIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2TbIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2PrIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [CoIII2YIII2{(py)C(Η)NO}4(piv)4(NO3)4].2MeCN [Cu2(diba)4(quinoxaline)]n [Cu3Dy2{(py)2CO2}{(py)2CO(OMe)}3{(py)2CO(OEt)}(NO3)4(H2O)2](ClO4)(OH) [Cu6{(py)2CO(OMe)}6(NO3)2](ClO4)4 [Cu3{(py)2C(OMe)(OH)}2{(py)2C(OMe)O}2(ClO4)2] (ClO4)2 .2MeOH [Cu{(py)2C(OH){(CH2COCH3)}2](NO3)2.2H2O The structures of the complexes have been solved with Single Crystal X-ray Crystallography. The magnetic properties of selected compounds are investigated. The complexes have been characterized by several physical and spectroscopic techniques. The data are discussed in terms of the known structures of the complexes and the coordination modes of the ligands.
287

Effects of land-use intensity in grasslands on diversity, life-history traits and multitrophic interactions / Auswrikungen der Landnutzungsintensität in Grünländern auf Diversität,

Börschig, Carmen 07 March 2012 (has links)
No description available.
288

Étude intracrânienne sur les mécanismes cérébraux permettant la reconnaissance d’objets

Bertrand, Josie-Anne 06 1900 (has links)
La reconnaissance d’objets est une tâche complexe au cours de laquelle le cerveau doit assembler de manière cohérente tous les éléments d’un objet accessible à l’œil afin de le reconnaître. La construction d’une représentation corticale de l’objet se fait selon un processus appelé « bottom-up », impliquant notamment les régions occipitales et temporales. Un mécanisme « top-down » au niveau des régions pariétales et frontales, facilite la reconnaissance en suggérant des identités potentielles de l’objet à reconnaître. Cependant, le mode de fonctionnement de ces mécanismes est peu connu. Plusieurs études ont démontré une activité gamma induite au moment de la perception cohérente de stimuli, lui conférant ainsi un rôle important dans la reconnaissance d’objets. Cependant, ces études ont utilisé des techniques d’enregistrement peu précises ainsi que des stimuli répétitifs. La première étude de cette thèse vise à décrire la dynamique spatio-temporelle de l’activité gamma induite à l’aide de l’électroencéphalographie intracrânienne, une technique qui possède des résolutions spatiales et temporelles des plus précises. Une tâche d’images fragmentées a été conçue dans le but de décrire l’activité gamma induite selon différents niveaux de reconnaissance, tout en évitant la répétition de stimuli déjà reconnus. Afin de mieux circonscrire les mécanismes « top-down », la tâche a été répétée après un délai de 24 heures. Les résultats démontrent une puissante activité gamma induite au moment de la reconnaissance dans les régions « bottom-up ». Quant aux mécanismes « top-down », l’activité était plus importante aux régions occipitopariétales. Après 24 heures, l’activité était davantage puissante aux régions frontales, suggérant une adaptation des procédés « top-down » selon les demandes de la tâche. Très peu d’études se sont intéressées au rythme alpha dans la reconnaissance d’objets, malgré qu’il soit bien reconnu pour son rôle dans l’attention, la mémoire et la communication des régions neuronales distantes. La seconde étude de cette thèse vise donc à décrire plus précisément l’implication du rythme alpha dans la reconnaissance d’objets en utilisant les techniques et tâches identiques à la première étude. Les analyses révèlent une puissante activité alpha se propageant des régions postérieures aux régions antérieures, non spécifique à la reconnaissance. Une synchronisation de la phase de l’alpha était, quant à elle, observable qu’au moment de la reconnaissance. Après 24 heures, un patron similaire était observable, mais l’amplitude de l’activité augmentait au niveau frontal et les synchronies de la phase étaient davantage distribuées. Le rythme alpha semble donc refléter des processus attentionnels et communicationnels dans la reconnaissance d’objets. En conclusion, cette thèse a permis de décrire avec précision la dynamique spatio-temporelle de l’activité gamma induite et du rythme alpha ainsi que d’en apprendre davantage sur les rôles potentiels que ces deux rythmes occupent dans la reconnaissance d’objets. / Recognizing objects is a complex task requiring the brain to assemble visual information in such a way that coherent perception can happen. Building a visual cerebral representation is done through a bottom-up process, involving mainly occipital and temporal areas. A top-down mechanism from parietal and frontal areas, is thought to facilitate recognition by taking into account expectations and generating possible candidates. However, the precise mechanisms by which all these processes are done are still unclear. Studies investigating induced gamma response were able to link this activity to coherent perception of objects, suggesting a significant role of this activity in object recognition. However, these studies used imprecise recording techniques and stimuli repetition. The first study of this thesis aimed at describing with more precision the induced gamma activity using intracranial encephalography and a fragmented images paradigm in which only new stimuli are presented. Moreover, the task was presented again 24 hours later to circumscribe top-down mechanisms. Results show that the induced gamma activity is highest at recognition in regions involved in bottom-up processes. Top-down mechanism involved occipito-parietal areas when images were presented for the first time. When images were presented again 24 hours later, frontal areas mediated top-down facilitation, suggesting that top-down mechanisms vary according to task demand. Alpha rhythm has been less clearly related to visual perception, but is nevertheless well known to be involved in attention, memory and long-distance brain communication. The second study of this thesis investigated the role of alpha rhythm in object recognition, using the same technique and task as in the first study. Time-frequency analysis revealed a strong alpha activity unspecific to recognition, which was propagating from posterior to anterior regions. Phase coherence analysis, however, showed significant phase synchronisation specific to recognition. A similar pattern of alpha activity was found 24 hours later. However, the activity was stronger in frontal regions and the phase synchronisation was more distributed. Alpha rhythm is thus thought to be involved in attentional and communicational mechanisms of object recognition. In conclusion, this thesis was able to describe the precise spatio-temporal dynamics of induced gamma and alpha activity and suggest potential roles of these rhythms in response to object recognition.
289

[en] BAYESIAN STOCHASTIC EXTENSION OF DETERMINISTIC BOTTOM-UP APPROACH FOR THE LONG TERM FORECASTING OF ENERGY CONSUMPTION / [pt] EXTENSÃO ESTOCÁSTICA BAYESIANA DA ABORDAGEM BOTTOM-UP DETERMINÍSTICA PARA A PREVISÃO DE LONGO PRAZO DO CONSUMO DE ENERGIA

FELIPE LEITE COELHO DA SILVA 16 February 2018 (has links)
[pt] O comportamento do consumo de energia elétrica do setor industrial tem sido amplamente investigado ao longo dos últimos anos, devido a sua importância econômica, social e ambiental. Mais especificamente, o consumo de eletricidade dos subsetores da indústria brasileira exerce grande importância para o sistema energético brasileiro. Neste contexto, as projeções de longo prazo do seu consumo de energia elétrica para um país ou uma região são informações de grande relevância na tomada de decisão de órgãos e entidades que atuam no setor energético. A abordagem bottom-up determinística tem sido utilizada para obter a previsão de longo prazo em diversas áreas de pesquisa. Neste trabalho, propõe-se uma metodologia que combina a abordagem bottom-up com os modelos lineares hierárquicos para a previsão de longo prazo considerando os cenários de eficiência energética. Além disso, foi utilizada a inferência bayesiana para a estimação dos parâmetros do modelo, permitindo a incorporação de incerteza nessas previsões. Os resultados utilizando os dados de consumo de eletricidade de subsetores da indústria brasileira mostraram que a metodologia proposta consegue capturar a tajetória do consumo de eletricidade, em particular, dos subsetores de papel e celulose, e de metais não-ferrosos e outros de metalurgia. Por exemplo, os intervalos de credibilidade de 95 por cento construídos a partir do modelo estocástico contemplam os valores reais observados nos anos de 2015 e 2016. / [en] The electricity consumption behaviour in the Brazilian industry has been extensively investigated over the past years due to its economic, social and environmental importance. Specifically, the electricity consumption of the subsectors of Brazilian industry have great importance for the Brazilian energy system. In this context, the long-term projections of energy consumption of a country or region are highly relevant information to decision-making of organs and entities operating in the energy sector. The deterministic bottom-up approach has been used for the long-term forecast in several areas of research. In this paper, we propose a methodology that combines the bottom-up approach with hierarchical linear models for long-term forecasting considering energy efficiency scenarios. In addition, Bayesian inference was used to estimate the parameters of the model, allowing the uncertainty incorporation in these forecasts. The results using the electricity consumption data from subsectors of the Brazilian industry showed that the proposed methodology is able to capture the trajectory of their electricity consumption, in particular of the pulp and paper, and of non-ferrous metals and other metallurgical subsectors. For example, the 95 percent credibility intervals constructed from the stochastic model contemplate the actual values observed in the years 2015 and 2016.
290

Estratégia atencional para busca visual e reconhecimento invariante de objetos baseada na integração de características bottom-up e top-down / Attentional strategy for visual search and invariant object recognition based on bottom-up and top-down feature integration

Evelina Maria de Almeida Neves 30 June 2000 (has links)
Uma das tarefas básicas dos mecanismos atencionais é decidir qual a localização dentro do campo visual, em que devemos prestar atenção primeiro. Um objeto que contenha características distintas, tais como orientação, forma, cor, tamanho, brilho, textura, etc. diferentes, pode atrair a atenção de uma maneira \"bottom-up\". A informação \"top-down\" baseia-se no conhecimento prévio e tem uma grande influência nas localizações atendidas. Inspirado nos mecanismos da Atenção Visual Humana, embora sem a pretensão de simulá-la, este trabalho prevê o desenvolvimento de uma nova metodologia que integra os dois tipos de informações: \"bottom-up\" e \"top-down\". Características \"bottom-up\" são geradas a partir de Momentos e essas informações são utilizadas em mapas de saliência, enquanto que um conhecimento prévio é utilizado para gerar pistas \"top-down\". Neste trabalho, desenvolveu-se uma metodologia específica para a busca e o reconhecimento visual em cenas com múltiplos objetos, utilizando para isso uma rede \"fuzzy\" contendo três subsistemas \"fuzzy\". Dada uma imagem de entrada, o objetivo consiste em se detectar regiões que possam conter informações mais significativas, a fim de que se possa guiar e restringir processamentos mais complexos. A inclusão de mecanismos de atenção (seleção de uma região de interesse dentro da imagem) é de fundamental importância pois os resultados obtidos pelo método podem ser usados para controlar a aquisição da imagem de uma maneira dinâmica. O modelo proposto está estruturado em três estágios principais: O primeiro estágio consiste em se segmentar os objetos e extrair características globais dos mesmos baseadas principalmente na teoria dos momentos, tais como tamanho, orientação, formato e distância e também média de nível de cinza. Por intermédio da comparação de um objeto com os outros presentes na cena, características \"bottom-up\" de conspicuidade são usadas para guiar a atenção ao objeto mais diferente. Por intermédio do uso da lógica \"fuzzy\" é possível inferir com grande flexibilidade algumas regras de decisão baseadas nos princípios de percepção visual tais como as leis Gestalt. O segundo estágio consiste de um subsistema \"fuzzy top-down\" que combina diferentes características de acordo com a relevância das mesmas em diferentes tarefas. Finalmente, o terceiro estágio consiste de um subsistema \"fuzzy\" que integra as informações obtidas dos subsistemas anteriores e fornece um índice geral de saliência, e indica a provável localização do objeto a ser reconhecido. A nova abordagem foi testada com objetos geométricos levando-se em consideração as características que atraem a atenção dos serem humanos / One of the basic tasks assigned to the human attentional mechanisms is to decide which location in the visual field we must pay attention first. An object containing distinctive features (such as different orientation, shape, color, size, shine, texture, etc.) can attract attention in a bottom-up way. Top-down information is based on the previous knowledge and has a large influence on the attended locations. Inspired on human visual attention mechanisms, although it doesn\'t want simulate it, this work presents a new methodology to integrate two different kind of information: bottom-up and top-down. Bottom-up features are obtained from Moment Theory and this information is used in salience maps, while a previous knowledge is used to create top-down hints. In this work, an specific methodology to visual search and recognition was developed to be applied to scenes containing multiple objects by a fuzzy net with three fuzzy subsystems. The aim of this methodology is to detect regions that may contain the most significant information, in order to guide and to restrict most complex processing. The inclusion of attentional mechanisms (the selection of a region of interest in the image) is fundamental and can be used to control the image acquisition in a dynamic way. The proposed model is structured in three main stages. The first stage segments the objects and extracts global features of them, based on the Moment Theory such as size, orientation, shape and distance and gray level average. By comparing one object with the other ones present in the scene, bottom-up features of conspicuity are used to guide the attention to the most different object. The Fuzzy Logic allows us to infer with great flexibility some of decision rules based on the visual perception principles such as the Gestalt Laws. The second stage is a top-down fuzzy subsystem that combines different features according to the relevance of them in different tasks. Finally, the third stage is a fuzzy subsystem that integrates the information obtained from the previous sub-systems and gives us a general salience index. The new methodology was tested in geometrical objects considering the feature that attracts attention to human beings

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