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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.
101

Characteristics of social networks in the Chinese Web

Yu, Louis Lei 04 October 2010 (has links)
We look at the underlying friendships and relationships between Chinese Internet users. We identify the presence and characteristics of the different types of online friendships and online relationships by analyzing various online social networks. First, we look at the concept of guanxi as it is applied to the interaction between web sites. Guanxi is a type of dyadic social interaction based on feelings and trust which has been well studied by scholars in China. We define guanxi in the web: particular linking patterns that appear in the web as well as supporting textual evidence in the web pages which we believe are indicative of the presence and varying strengths of the underlying guanxi between Chinese web site owners. Through our empirical study of the Chinese web, the general web, and the Japanese, Iranian, and French web, we show that guanxi between web sites is a more prevalent feature in the Chinese web. Next, we study the formation of online friendships in Douban, an online social networking platform frequently used by the youth in China. We look at several factors that can affect the evolution of friendships such as having memberships in the same discussion groups and sharing common interests or common friends. We compare these factors in influencing the formation of online friendships. Our work provides the first study on the underlying relationships between web sites in the Chinese web and the first large scale empirical analysis on the evolution of friendships in a Chinese online social network.
102

Etudes expérimentales et numériques du comportement des dalles épaisses en béton armé sous chargement de cisaillement et interaction cisaillement/effet de membrane : Application aux bâtiments nucléaires / Experimental and numerical studies of shear behavior of thick reinforced concrete slabs and shear/membrane effect interaction : Application to nuclear buildings

Nana, Wendpanga Serge Auguste 20 November 2017 (has links)
Cette contribution, en s’appuyant sur expérimentation et modélisation numérique vise à une meilleure compréhension du comportement des dalles en béton armé sous sollicitations de cisaillement. Une campagne expérimentale a été réalisée sur des dalles épaisses à pleine échelle de centrales nucléaires. Ces dalles sans armatures d’effort tranchant sont soumises à une sollicitation de cisaillement en chargement quasi-statique. Les essais sont réalisés en faisant varier différents paramètres qui peuvent influencer le comportement au cisaillement. Sont ainsi étudiés : résistance en compression du béton, épaisseur, taux d’armatures longitudinales et transversales, taille des granulats, longueur de la plaque de chargement. L’influence des efforts de membrane, de compression ou de traction, sur le comportement au cisaillement a également été analysée. Les résultats des essais sont ensuite comparés aux prédictions des codes de calcul. Ces résultats ont d’abord permis d’apporter une réponse aux divergences qui existent entre l’Eurocode 2 et l’Annexe Nationale Française quant à la prédiction du cisaillement. Ont également été évalués le niveau de précision donné par d’autres normes de dimensionnement au cisaillement: la norme américaine ACI 318-14, le code nucléaire AFCEN ETC-C 2010, le fib-Model Code 2010 et l’approche par la théorie de la fissure critique de cisaillement CSCT. Ensuite est évalué la possibilité d’analyses non-linéaire par élément finis (EF) pour reproduire le phénomène du cisaillement dans les dalles. Un modèle de béton élastoplastique avec endommagement est combiné à une analyse quasi-statique à schéma de résolution explicite. Des lois de comportement non linéaires appropriées du béton avec des comportements post-pic associés à un critère énergétique ont été considérées. La bonne concordance entre le modèle proposé et les résultats expérimentaux en termes de résistance au cisaillement et de modes de rupture permet de valider la modélisation proposée. Une étude paramétrique a été réalisée sur la base du modèle proposé avec les mêmes propriétés mécaniques de béton. Des lois simplifiées permettant d’estimer les capacités en cisaillement en fonction des différents paramètres étudiés sont finalement proposées. / This study, based on experiments and numerical modeling, aims at a better understanding of the shear behavior of reinforced concrete slabs. An experimental campaign was carried out on full-scale thick slabs typical of nuclear power plant slabs. These slabs without shear reinforcement are subjected to a quasi-static shear loading. The tests are carried out by varying different parameters that can influence the shear behavior: the concrete compressive strength, the slab depth, the bottom longitudinal and transverse reinforcement ratio, the concrete aggregate size, the loading plate length. The influence on shear behavior of compression or tension membrane forces has also been analyzed. The results of tests are then compared with the predictions of the calculation codes. These results first of all helped to answer the differences between the Eurocode 2 and the French National Annex concerning the prediction of the shear capacity of reinforced concrete slabs. The level of accuracy given by other shear dimensioning standards was also assessed: The American standard ACI 318-14, the AFCEN ETC-C 2010 code used for nuclear buildings, the fib-Model 2010 and the Critical Shear Crack Theory. Next, we evaluate the possibilities of a non-linear finite element analysis (EF) to reproduce the phenomenon of shear in slabs. An elastoplastic concrete model with damage was used and combined with a quasi-static analysis using an explicit resolution scheme. Appropriate nonlinear behavior laws of concrete with post-peak behaviors associated with an energy criterion were considered. The good agreement between the proposed model and the experimental results in terms of shear strength and failure modes allowed validating the proposed modeling. A parametric study was conducted based on the numerical proposed model with the same mechanical properties of concrete. Simplified laws allowing estimating the shear capacities according to the different parameters studied are proposed.
103

Uplatnění procesního způsobu řízení výroby ve vybraném podniku / The application process for the management of production in the selected company

PINCOVÁ, Kristýna January 2014 (has links)
The subject of the thesis "The application of process for the management of production in the selected company (Banes Ltd.)" is an exploration and mapping of processes in the company Banes Ltd. occur. The first part covers the theoretical basis of the subject, particularly the definition of basic concepts of processes, quality and selection of technologies, systems and methods used by Banes Ltd. The second part is about describing the company Banes Ltd. The theoretical knowledge is applied in the analysis of the structure of processes, defining processes and their analysis in the company Banes Ltd. In the last section are applied statistical analyses of quality.
104

Síntese e cristaloquímica do 1-(4-carboxifenil)-3-(4-acetilamidofenil)triazeno e complexos de cobre(i), prata(I) e ouro(I) com o ligante 1-(4-nitrofenil)-3-(4-etoxicarboxifenil)triazenido / Synthesis and crystalchemistry of 1-(4-carboxyphenyl)-3-(4-acetylamidophenyl)triazene and complexes of copper(I), silver(i) and gold(I) with 1-(4-ethoxycarbonylphenyl)-3-(4-nitrophenyl)triazenide ligand

Amaral, Carlos Henrique Oliveira do 05 December 2007 (has links)
This work deals with the determination of the single crystal structure analysis of four triazenido complexes including gold(I), copper(I), silver(I), and the crystal structure of a free triazene molecule. Crystal data and refinement indices of 1-(4-carboxyphenyl)-3-(4- acetylamidophenyl)triazene (1) are: monoclinic system, space group P21/n, cell parameters a = 7.772(1), b = 9.7365(2), c = 19.55(3) Å, β = 93.435(1)º, Z = 4, R1 = 0.0394, wR2 = 0.0632. The crystal structure show that the molecule deviates significantly from planarity (r.m.s. 0.342 Å). The molecules of (1) are associated to a bi-dimensional supramolecular array in form of helix chains including classic hydrogen bonding in the [010] crystallographic direction. Crystal data and refinement indices of 1-(4-ethoxycarbonylphenyl)-3-(4-nitrophenyl)triazenide(triphenylphosfine)gold(I) (3) are: triclinic system, space group P(-1), cell parameters a = 9.8837(2), b = 12.6159(2), c = 13.0948(2) Å, α = 79,160(1)°, β = 78,411(1)°, γ = 73,731(1)°, Z = 2, R1 = 0.0271, wR2 = 0.0588. One deprotonated triazenido ligand and one triphenylphosfine molecule built the linear coordination geometry of gold(I). Crystal data and refinement indices of 1-(4-ethoxycarbonylphenyl)-3-(4-nitrophenyl)-bis-(triphenylphosfine)copper(I) (4) are: triclinic system, space group P(-1), cell parameters a = 10.9853(2), b = 14.6006(3), c = 16.0638(3) Å, α = 79.160(1)°, β = 78.411(1)°, γ = 73.731(1)°, Z = 2, R1 = 0.0370, wR2 = 0.0996. One deprotonated triazenido ligand and three neutral triphenylfosfine molecules complete the distorted tetrahedral coordination sphere of copper(I). Crystal data and refinement indices of trans-bis-1-(4-ethoxycarbonylphenyl)-3-(4-nitrophenyl)triazenide-bis-(pyridine)silver(I) (5) are: triclinic system, space group P(-1) with cell parameters a = 9.3123(4), b = 11.1234(5), c = 11.1914(5) Å, α = 71.165(3)°, β = 68.723(3)°, γ= 89.530(3)°, Z = 2, R1 = 0.0383 wR2 = 0.0856. Two deprotonated monodentate triazenido ligands and two pyridine molecules in trans position relative to each other in a eight-membered Ag2N6 fragment, perform the Tcoordination geometry of each silver(I) ion. Crystal data and refinement indices of Catena-[bis(μ2-ciano)-bis(triphenilphosfine)-di-silver(I)] (6) are: monoclinic system, space group P21/n with cell parameters a = 9.3174(4), b = 22.931(1), c = 16.1513(8) Å, β = 99.759(3)°, Z = 4, R1 = 0.0526, wR2 = 0.1337. Two neutral triphenilfosfine molecules and two cyanide ligands support the distorted tetrahedral coordination geometry of the silver(I) ion in a open catenated coordination polymer. / Este trabalho apresenta a determinação da estrutura cristalina e molecular de quatro complexos sendo um com ouro(I), outro com cobre(I) e dois complexos de prata(I), adicionalmente incluindo a estrutura cristalina e molecular de um composto triazeno livre O composto 1-(4-carboxifenil)-3-(4-acetilamidofenil)triazeno(1) cristaliza no sistema monoclínico, grupo espacial P21/n, com parâmetros de cela a = 7,7723(10) Å, b = 9,7365(2) Å, c = 19,355(3) Å, β = 93,4350(10)º, V = 1462,09(4) Å3, Z = 4, R1 = 0,0394, wR2 = 0,1093. A estrutura cristalina do pró-ligante (1) revela que a molécula não é planar (r.s.m. 0,3148Å) e que, as moléculas unem-se por ligações de hidrogênio na direção cristalográfica [010]. As ligações de hidrogênio são do tipo clássicas N H O, O H O e O H N, que se relacionam por operações de simetria formando um arranjo bidimensional. O composto (3) cristaliza do sistema triclínico, grupo espacial P(-1) com parâmetros de cela a = 9,8837(2) Å, b = 12,6159(2) Å, c = 13,0948(2) Å; α= 79,1600(10)°, β= 78,4110(10)°, γ = 73,7310(10)°; V = 1520,32(5) Å3 ; Z = 2. O refinamento desta estrutura conduziu aos índices de discordância R1 = 0,0271, wR2 = 0,0588. A esfera de coordenação do íon ouro(I) é formada por um ligante triazeno desprotonado e uma moléculas de trifenilfosfina. O composto (4) cristaliza no sistema triclínico, grupo espacial P(-1) com parâmetros de cela a = 10,9853(2) Å, b = 14,6006(3) Å , c = 16,0638(3) Å, α = 97,1150(10)°, β = 102,9530(10)°, γ = 110,8030(10)°; V = 2287,95(8) Å3 ; Z = 2. O refinamento desta estrutura conduziu aos índices de discordância R1 = 0,0370, wR2 = 0,0996. A esfera de coordenação do íon cobre(I) é formada por um ligante triazeno desprotonado e duas moléculas de trifenilfosfina. O composto (5) binuclear cristaliza no sistema triclínico, grupo espacial P (-1) com parâmetros de cela a = 9,3123(4) Å, b = 11,1234(5) Å, c = 11,1914(5) Å, α = 71,165(3)°, β = 68,723(3)°, γ = 89,530(3)°; V = 1014,56(8) Å3 ; Z = 2. O refinamento desta estrutura demonstrou os índices de discordância R1 = 0,0383, wR2 = 0,0856. A esfera de coordenação do íon prata(I) é formada por dois ligantes triazenos desprotonados e duas moléculas de piridina. O composto (6) polímero cristaliza no sistema monoclínico, grupo espacial P21/n com parâmetros de cela a = 9,3174(4) Å, b = 22,9314(14) Å, c = 16,1513(8) Å, β = 99,759 (3)°; V = 3401,0(3) Å3 ; Z = 4. O refinamento desta estrutura atingiu os índices de discordância R1 = 0,0526, wR2 = 0,1337. A esfera de coordenação do íon prata(I) é formada por dois ligantes trifenilfosfina e dois cianetos.
105

Protein Structure Networks : Implications To Protein Stabiltiy And Protein-Protein Interactions

Brinda, K V 08 1900 (has links) (PDF)
No description available.
106

Hypervalent diorganoantimony(III) fluorides via diorganoantimony(III) cations – a general method of synthesis

Preda, Ana Maria, Raţ, Ciprian I., Silvestru, Cristian, Lang, Heinrich, Rüffer, Tobias, Mehring, Michael 18 February 2016 (has links)
Novel diorganoantimony(III) fluorides containing ligands with pendant arms, R2SbF (5), (R)PhSbF (6) [R = 2-(2′,6′-iPr2C6H3N[double bond, length as m-dash]CH)C6H4], R′′2SbF (7) and (R′′)PhSbF (8) [R′′ = 2-(Me2NCH2)C6H4], were prepared via the ionic derivatives [R2Sb]+[PF6]− (1), [(R)PhSb]+[PF6]− (2), [R′′2Sb]+[SbF6]− (4) and [(R′′)PhSb]+[SbF6]− (obtained in situ) by treatment with [Bu4N]F·3H2O. The ionic species used as starting materials as well as [R′2Sb]+[PF6]− (3) [R′ = 2-(2′,4′,6′-Me3C6H2N[double bond, length as m-dash]CH)C6H4] were obtained from the corresponding bromides or chlorides and Tl[PF6] or Ag[SbF6]. The compounds were investigated by multinuclear NMR spectroscopy in solution, MS and IR spectroscopy in the solid state. The molecular structures of the ionic species 1·2CH2Cl2 and 3·2CHCl3 as well as of the fluorides 5–8 were determined by single-crystal X-ray diffraction. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
107

Some aspects of convection as well as graphite and carbide formations during casting.

Khan, Fareed Ashraf January 2018 (has links)
It is an established fact that segregation during casting affects the physical properties of carbon-based ferro alloys; this motivates the study of the segregation behaviour of carbon and carbide-forming solute elements. In this context, this thesis investigates two different situations: the effects of cooling rate and turbulence on the precipitation behaviour of the graphite nodules in nodular cast iron; the nature of carbide precipitation in a bearing steel grade and the effects of subsequent soaking on these carbides. The structures of boiling water reactor inserts cast by the uphill and downhill casting of nodular cast iron were examined. The samples were taken from representative locations in the top, middle and bottom cross sections of the castings. It was observed that in uphill-cast inserts the nodules were larger but fewer in number the bottom section, whereas in downhill-cast inserts the nodules in the bottom section were smaller, but greater in number. Variation in volume fraction of the graphite nodules across the inserts was also observed. The probable cause of this variation was the difference in cooling rate in different sections of the insert. Between the steel tubes located at the central part of the casting, the fraction of graphite was lower, which could be the result of carburization of the steel tubes. To study the effects of melt stirring during the solidification of nodular cast iron, several experiments were conducted at variable cooling rates and for different stirring times. Examination of the microstructure was conducted using Light Optical Microscope (LOM) and Scanning Electron Microscope (SEM). It was observed that during stirring the melt oxidized and oxide nuclei were formed. The number of nucleation sites for the precipitation of graphite nodules increased, which raised the nodule count and the fraction of the graphite precipitated. The matrix transformed from pearlite to ferrite, which could be due to the fact that more carbon had diffused out of the matrix. The segregation behaviour in hypereutectoid bearing steel produced by ingot casting was also studied. The effects of soaking on micro and macro segregation was investigated in samples taken from as cast and soaked ingots; emphasis was laid on the bulk matrix and A-segregation channels. Samples were also taken from ingots which were soaked and then hot worked. The micro and macro examination of the microstructure was conducted using LOM and SEM. Quantitative and qualitative composition analysis was performed using Energy-dispersive X-ray spectroscopy (EDX) and an electron micro probe analyzer (EMPA). It was observed that M3C, M2C and M6C had precipitated. The carbide morphology in the bulk matrix was different to that in the A-segregation channels. All the primary carbides in the bulk matrix were found to have dissolved after 4 hours of soaking at 1200oC. / Det är ett faktum att segringar som uppstår under gjutning påverkar materialegenskaperna hos kolbaserade järnlegeringar; detta utgör motivationen till studien av segringsuppträdandet hos kol och karbidbildande ämnen. Denna avhandling behandlar två olika aspekter inom ramen för detta ämne: påverkan av kylningshastighet och turbulens på kärnbildningen av grafitnoduler i nodulärt gjutjärn samt karbidbildning i kullagerstål och dess påverkan på den efterföljande värmebehandlingen av dessa karbider. Strukturen hos rör till vattenkokare som tillverkats av nodulärt gjutjärn som gjutits med fyllning från botten eller från toppen undersöktes. Prover togs från representativa tvärsnittspositioner från toppen, mitten och botten av de gjutna ämnena. Resultaten visade att användandet av bottenfyllda kokiller gav upphov till större men färre karbider i nedre delen av ämnet, medans användandet av toppfyllda kokiller gav upphov till mindre men fler karbider i nedre delen av ämnet. Variationer av volymfraktionen av grafitnoduler längs tvärsnitten observerades också. Den mest sannolika orsaken till denna variation var skillnaden i kylhastighet i de olika områdena av tvärsnitten. Hos rör tillverkade av det centrala delen av ämnet så var fraktionen grafit lägre, vilket kan bero på en uppkolning av rören. Ett flertal experiment utfördes med varierande kylningshastigheter och olika omrörningstider för att studera inverkan av omrörning av smältan på stelningen av nodulärt gjutjärn. Studier av mikrostrukturen genomfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Resultaten visade att smältan oxiderades under omrörningen, vilket resulterade i bildandet av oxider. Detta ledde till en ökning av kärnbildningsområden för grafitnoduler, vilket ledde till en ökning av antalet noduler samt fraktionen av grafit som fälldes ut. Strukturen omvandlades från perlit till ferrit, vilket troligen orsakades av att kol hade diffunderat ut från strukturen. Segringsbeteendet hos hypereutektoida kullagerstål tillverkade genom götgjutning undersöktes också. Effekten av värmebehandling på mikro- och makrosegringar undersöktes i prover tagna från gjutna och värmebehandlade ämnen. Fokus var på att studera strukturen i ämnena samt A-segringar. Dessutom togs prover från ämnen som först värmebehandlats och därefter varmbearbetats. Både mikro- och makroundersökningar av mikrostrukturen utfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Dessutom så genomfördes kvantitativa sammansättningsbestämningar med energidispersiv röntgenspektroskopi och elektronmikroprobsanalys. Resultaten visade att M3C, M2C och M6C karbider hade fällts ut. Karbidmorfologin i huvuddelen av strukturen skiljde sig från den som återfanns i A-segringar. Samtliga primära karbider i huvuddelen av strukturen hade lösts upp efter 4 timmars värmebehandling vid 1200oC. / <p>QC 20180523</p>
108

Analysis of Flame Blow-Out in Turbulent Premixed Ammonia/Hydrogen/Nitrogen - Air Combustion

Lakshmi Srinivasan (14228177) 08 December 2022 (has links)
<p>  </p> <p>With economies shifting towards net-zero carbon emissions, there is an increased interest in carbon-free energy carriers. Hydrogen is a potential carbon-free energy source. However, it poses several production, infrastructural, and safety challenges. Ammonia blends have been identified as a potential hydrogen carrier and fuel for gas turbine combustion. Partially cracked ammonia mixtures consist of large quantities of hydrogen that help overcome the disadvantages of pure ammonia combustion. The presence of nitrogen in the fuel blends leads to increased NO<sub>x</sub> emissions, and therefore lean premixed combustion is necessary to curb these emissions. Understanding the flame features, precursors, and dynamics of blowout of such blends due to lean conditions is essential for stable operation, lean blowout prediction, and control. </p> <p><br></p> <p>In this study, high-fidelity large eddy simulations for turbulent premixed ammonia/hydrogen/nitrogen-air flames in an axisymmetric, unconfined, bluff-body stabilized burner are performed to gain insights into lean blowout dynamics. Partially cracked ammonia (40% NH<sub>3</sub>, 45% H<sub>2</sub>, and 15% N<sub>2</sub>, by volume) is chosen as fuel since its laminar burning velocity is comparable to CH4-air mixtures. A finite rate chemistry model with a detailed chemical kinetic mechanism (36 species and 247 reactions) is utilized to capture characteristics of various species during blowout. A comprehensive study of the flow field and flame structure for a weakly stable burning at an equivalence ratio of 0.5 near the blowout limit is presented. Further, the effects of blowout on the heat release rate, vorticity, distribution of major species, and ignition radicals are studied at four time instances at blowout velocity of 70 m/s. Since limited data is available on turbulent premixed combustion of partially cracked ammonia, such studies are essential in understanding flame behavior and uncertainties with regard to blowout.</p>
109

Reducing software complexity by hidden structure analysis : Methods to improve modularity and decrease ambiguity of a software system

Bjuhr, Oscar, Segeljakt, Klas January 2016 (has links)
Software systems can be represented as directed graphs where components are nodes and dependencies between components are edges. Improvement in system complexity and reduction of interference between development teams can be achieved by applying hidden structure analysis. However, since systems can contain thousands of dependencies, a concrete method for selecting which dependencies that are most beneficial to remove is needed. In this thesis two solutions to this problem are introduced; dominator- and cluster analysis. Dominator analysis examines the cost/gain ratio of detaching individual components from a cyclic group. Cluster analysis finds the most beneficial subgroups to split in a cyclic group. The aim of the methods is to reduce the size of cyclic groups, which are sets of co- dependent components. As a result, the system architecture will be less prone to propagating errors, caused by modifications of components. Both techniques derive from graph theory and data science but have not been applied to the area of hidden structures before. A subsystem at Ericsson is used as a testing environment. Specific dependencies in the structure which might impede the development process have been discovered. The outcome of the thesis is four to-be scenarios of the system, displaying the effect of removing these dependencies. The to-be scenarios show that the architecture can be significantly improved by removing few direct dependencies. / Mjukvarusystem kan representeras som riktade grafer där komponenter är noder och beroenden mellan komponenter är kanter. Förbättrad systemkomplexitet och minskad mängd störningar mellan utvecklingsteam kan åstadkommas genom att applicera teorin om gömda beroende. Eftersom system kan innehålla tusentals beroenden behövs en konkret metod för att hitta beroenden i systemet som är fördelaktiga att ta bort. I den här avhandlingen presenteras två lösningar till problemet; dominator- och klusteranalys. Dominatoranalys undersöker kostnad/vinst ration av att ta bort individuella komponenter i systemet från en cyklisk grupp. Klusteranalys hittar de mest lönsamma delgrupperna att klyva isär i en cyklisk grupp. Metodernas mål är att minska storleken på cykliska grupper. Cykliska grupper är uppsättningar av komponenter som är beroende av varandra. Som resultat blir systemarkitekturen mindre benägen till propagering av fel, orsakade av modifiering av komponenter. Båda metoderna härstammar från grafteori och datavetenskap men har inte applicerats på området kring gömda strukturer tidigare. Ett subsystem på Ericsson användes som testmiljö. Specifika beroenden i strukturen som kan vara hämmande för utvecklingsprocessen har identifierats. Resultatet av avhandlingen är fyra potentiella framtidsscenarion av systemet som visualiserar effekten av att ta bort de funna beroendena. Framtidsscenariona visar att arkitekturen kan förbättras markant genom att avlägsna ett fåtal direkta beroenden.
110

Estimation de la structure de morceaux de musique par analyse multi-critères et contrainte de régularité / Music structure estimation using multi-criteria analysis and regularity constraints

Sargent, Gabriel 21 February 2013 (has links)
Les récentes évolutions des technologies de l'information et de la communication font qu'il est aujourd'hui facile de consulter des catalogues de morceaux de musique conséquents. De nouvelles représentations et de nouveaux algorithmes doivent de ce fait être développés afin de disposer d'une vision représentative de ces catalogues et de naviguer avec agilité dans leurs contenus. Ceci nécessite une caractérisation efficace des morceaux de musique par l'intermédiaire de descriptions macroscopiques pertinentes. Dans cette thèse, nous nous focalisons sur l'estimation de la structure des morceaux de musique : il s'agit de produire pour chaque morceau une description de son organisation par une séquence de quelques dizaines de segments structurels, définis par leurs frontières (un instant de début et un instant de fin) et par une étiquette représentant leur contenu sonore.La notion de structure musicale peut correspondre à de multiples acceptions selon les propriétés musicales choisies et l'échelle temporelle considérée. Nous introduisons le concept de structure “sémiotique" qui permet de définir une méthodologie d'annotation couvrant un vaste ensemble de styles musicaux. La détermination des segments structurels est fondée sur l'analyse des similarités entre segments au sein du morceau, sur la cohérence de leur organisation interne (modèle “système-contraste") et sur les relations contextuelles qu'ils entretiennent les uns avec les autres. Un corpus de 383 morceaux a été annoté selon cette méthodologie et mis à disposition de la communauté scientifique.En termes de contributions algorithmiques, cette thèse se concentre en premier lieu sur l'estimation des frontières structurelles, en formulant le processus de segmentation comme l'optimisation d'un coût composé de deux termes~: le premier correspond à la caractérisation des segments structurels par des critères audio et le second reflète la régularité de la structure obtenue en référence à une “pulsation structurelle". Dans le cadre de cette formulation, nous comparons plusieurs contraintes de régularité et nous étudions la combinaison de critères audio par fusion. L'estimation des étiquettes structurelles est pour sa part abordée sous l'angle d'un processus de sélection d'automates à états finis : nous proposons un critère auto-adaptatif de sélection de modèles probabilistes que nous appliquons à une description du contenu tonal. Nous présentons également une méthode d'étiquetage des segments dérivée du modèle système-contraste.Nous évaluons différents systèmes d'estimation automatique de structure musicale basés sur ces approches dans le cadre de campagnes d'évaluation nationales et internationales (Quaero, MIREX), et nous complétons cette étude par quelques éléments de diagnostic additionnels. / Recent progress in information and communication technologies makes it easier to access large collections of digitized music. New representations and algorithms must be developed in order to get a representative overview of these collections, and to browse their content efficiently. It is therefore necessary to characterize music pieces through relevant macroscopic descriptions. In this thesis, we focus on the estimation of the structure of music pieces : the goal is to produce for each piece a description of its organization by means of a sequence of a few dozen structural segments, each of them defined by its boundaries (starting time and ending time) and a label reflecting its audio content.The notion of music structure corresponds to a wide range of meanings depending on the musical properties and the temporal scale under consideration. We introduce an annotation methodology based on the concept of “semiotic structure" which covers a large variety of musical styles. Structural segments are determined through the analysis of their similarities within the music piece, the coherence of their inner organization (“system-contrast" model) and their contextual relationship. A corpus of 383 pieces has been annotated according to this methodology and released to the scientific community.In terms of algorithmic contributions, this thesis concentrates in the first place on the estimation of structural boundaries. We formulate the segmentation process as the optimization of a cost function which is composed of two terms. The first one corresponds to the characterization of structural segments by means of audio criteria. The second one relies on the regularity of the target structure with respect to a “structural pulsation period". In this context, we compare several regularity constraints and study the combination of audio criteria through fusion.Secondly, we consider the estimation of structural labels as a probabilistic finite-state automaton selection process : in this scope, we propose an auto-adaptive criterion for model selection, applied to a description of the tonal content. We also propose a labeling method derived from the system-contrast model.We evaluate several systems for structural segmentation of music based on these approaches in the context of national and international evaluation campaigns (Quaero, MIREX). Additional diagnostic is finally presented to complement this work.

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