Global ETD Search

231	Joint Source-Channel Coding Reliability Function for Single and Multi-Terminal Communication Systems Zhong, Yangfan 15 May 2008 (has links) Traditionally, source coding (data compression) and channel coding (error protection) are performed separately and sequentially, resulting in what we call a tandem (separate) coding system. In practical implementations, however, tandem coding might involve a large delay and a high coding/decoding complexity, since one needs to remove the redundancy in the source coding part and then insert certain redundancy in the channel coding part. On the other hand, joint source-channel coding (JSCC), which coordinates source and channel coding or combines them into a single step, may offer substantial improvements over the tandem coding approach. This thesis deals with the fundamental Shannon-theoretic limits for a variety of communication systems via JSCC. More specifically, we investigate the reliability function (which is the largest rate at which the coding probability of error vanishes exponentially with increasing blocklength) for JSCC for the following discrete-time communication systems: (i) discrete memoryless systems; (ii) discrete memoryless systems with perfect channel feedback; (iii) discrete memoryless systems with source side information; (iv) discrete systems with Markovian memory; (v) continuous-valued (particularly Gaussian) memoryless systems; (vi) discrete asymmetric 2-user source-channel systems. For the above systems, we establish upper and lower bounds for the JSCC reliability function and we analytically compute these bounds. The conditions for which the upper and lower bounds coincide are also provided. We show that the conditions are satisfied for a large class of source-channel systems, and hence exactly determine the reliability function. We next provide a systematic comparison between the JSCC reliability function and the tandem coding reliability function (the reliability function resulting from separate source and channel coding). We show that the JSCC reliability function is substantially larger than the tandem coding reliability function for most cases. In particular, the JSCC reliability function is close to twice as large as the tandem coding reliability function for many source-channel pairs. This exponent gain provides a theoretical underpinning and justification for JSCC design as opposed to the widely used tandem coding method, since JSCC will yield a faster exponential rate of decay for the system error probability and thus provides substantial reductions in complexity and coding/decoding delay for real-world communication systems. / Thesis (Ph.D, Mathematics & Statistics) -- Queen's University, 2008-05-13 22:31:56.425 Common and private message Common randomization Correlated sources Discrete memoryless sources and channels Error exponent Excess distortion exponent Feedback Fenchel transform Probability of error Probability of excess distortion Fenchel duality theorem Hamming distortion measure Joint source-channel coding Markov types Multiple-access channel Reliability function Separation principle Stationary ergodic Mrkov source/channel Tandem coding Type packing lemma Broadcast channel
232	Variational and Ergodic Methods for Stochastic Differential Equations Driven by Lévy Processes Gairing, Jan Martin 03 April 2018 (has links) Diese Dissertation untersucht Aspekte des Zusammenspiels von ergodischem Langzeitver- halten und der Glättungseigenschaft dynamischer Systeme, die von stochastischen Differen- tialgleichungen (SDEs) mit Sprüngen erzeugt sind. Im Speziellen werden SDEs getrieben von Lévy-Prozessen und der Marcusschen kanonischen Gleichung untersucht. Ein vari- ationeller Ansatz für den Malliavin-Kalkül liefert eine partielle Integration, sodass eine Variation im Raum in eine Variation im Wahrscheinlichkeitsmaß überführt werden kann. Damit lässt sich die starke Feller-Eigenschaft und die Existenz glatter Dichten der zuge- hörigen Markov-Halbgruppe aus einer nichtstandard Elliptizitätsbedingung an eine Kom- bination aus Gaußscher und Sprung-Kovarianz ableiten. Resultate für Sprungdiffusionen auf Untermannigfaltigkeiten werden aus dem umgebenden Euklidischen Raum hergeleitet. Diese Resultate werden dann auf zufällige dynamische Systeme angewandt, die von lin- earen stochastischen Differentialgleichungen erzeugt sind. Ruelles Integrierbarkeitsbedin- gung entspricht einer Integrierbarkeitsbedingung an das Lévy-Maß und gewährleistet die Gültigkeit von Oseledets multiplikativem Ergodentheorem. Damit folgt die Existenz eines Lyapunov-Spektrums. Schließlich wird der top Lyapunov-Exponent über eine Formel der Art von Furstenberg–Khasminsikii als ein ergodisches Mittel der infinitesimalen Wachs- tumsrate über die Einheitssphäre dargestellt. / The present thesis investigates certain aspects of the interplay between the ergodic long time behavior and the smoothing property of dynamical systems generated by stochastic differential equations (SDEs) with jumps, in particular SDEs driven by Lévy processes and the Marcus’ canonical equation. A variational approach to the Malliavin calculus generates an integration-by-parts formula that allows to transfer spatial variation to variation in the probability measure. The strong Feller property of the associated Markov semigroup and the existence of smooth transition densities are deduced from a non-standard ellipticity condition on a combination of the Gaussian and a jump covariance. Similar results on submanifolds are inferred from the ambient Euclidean space. These results are then applied to random dynamical systems generated by linear stochas- tic differential equations. Ruelle’s integrability condition translates into an integrability condition for the Lévy measure and ensures the validity of the multiplicative ergodic theo- rem (MET) of Oseledets. Hence the exponential growth rate is governed by the Lyapunov spectrum. Finally the top Lyapunov exponent is represented by a formula of Furstenberg– Khasminskii–type as an ergodic average of the infinitesimal growth rate over the unit sphere. Levy Prozess Malliavin Kalkül Poisssonsches Zufallsmass Bismut-Elworthy-Li Formel Ergodentheorie Lyapunov Exponent exponentielle Wachstumsrate Furstenberg-Khasminskii Formel zufällige dynamische Systeme Levy process Malliavin calculus Poisson random measure Bismut-Elworthy-Li formula Ergodic theory Lyapunov exponents exponential growth rate Furstenberg-Khasminskii formula random dynamical systems 510 Mathematik 516 Geometrie 515 Analysis SK 820 ddc:510 ddc:516 ddc:515 ddc:519
233	Financial Models of Interaction Based on Marked Point Processes and Gaussian Fields / Modellierung von Interaktionseffekten in Finanzdaten mittels Markierter Punktprozesse und Gaußscher Zufallsfelder Malinowski, Alexander 18 December 2012 (has links) No description available. 510 Mathematik Mathematics and Computer Science Markierter Punktprozess Interaktion Transaktionsdaten nicht-ergodisch Tailindex max-stabiler Prozess Peaks-Over-Threshold marked point process mark-location dependence transaction data high-frequency data non-ergodic tail index max-stable process peaks-over-threshold 31.70 Wahrscheinlichkeitsrechnung
234	トカマクプラズマにおけるプラズマ回転の動的形成過程上杉, 喜彦, 高村, 秀一, 大野, 哲靖, 叶, 民友 03 1900 (has links) 科学研究費補助金研究種目:基盤研究(B)(2) 課題番号:11480113 研究代表者:上杉喜彦研究期間:1999-2001年度 Dynamic Ergodic Divertor E × B Plasma Rotation EXBシアーフロー Electric Field Shear Electrode Biasing E×Bプラズマ回転 Fast Feedback Control IGBT Inverter Power Supply IGBTインバータ IGBTインバータ電源 Plasma Rotation Rotating Helical Magnetic Field アルフヴェン共鳴インバータ電源エルゴディックダイバータプラズマ回転回転ヘリカル摂動磁場回転ヘリカル磁場磁気島電場シアー電極バイアス高速フィードバック制御
235	Compounding the Problem? : Gated Communities in Climate and Environmental Disaster Fiction / Att bygga in problem? : Grindsamhällen i berättelser om klimat- och miljökatastrofer Walsh, Ryan Nicholas January 2023 (has links) The gated community motif occurs frequently within climate and environmental disaster fiction. This thesis investigates its occurrence across three media to establish how the gated community mode of living, as rendered in post-apocalyptic speculative fiction, responds to the threat and consequences of climate and environmental crisis. This thesis combines recent urban studies scholarship with ecocritical theory to analyse the gated communities present in Octavia E. Butler’s novels, The Parable of the Sower and The Parable of the Talents, Neil Blomkamp’s film, Elysium, and Naughty Dog’s video games, The Last of Us and The Last of Us: Part II. Comparative analysis of the motif in each primary narrative reveals how disaster exacerbates the security and segregation this mode of settlement makes possible, resulting in a pronounced Othering of outsiders to these communities. This essay concludes that the boundaries of these speculative gated communities come to symbolise the borders Global North, which rhetorically and physically exclude the migrant Other. As most of the gated communities in these narratives experience catastrophe and collapse at the hands of those they refuse to accept, the texts appear to warn us to expect similar results unless issues of climate justice are not addressed by the Global North today. / Grindsamhället (eng. gated community) är ett vanligt förekommande motiv i berättelser om klimat- och miljökatastrofer. Den här uppsatsen undersöker motivet i tre medietyper för att diskutera hur grindsamhället som samhällsform porträtteras i postapokalyptiskt spekulativ fiktion, och hur det ses svara på klimat- och miljö- krisernas hot och konsekvenser. Uppsatsen kombinerar ekokritisk teori med modern forskning inom urbana studier för att analysera grindsamhällen som förekommer i romanerna The Parable of the Sower och The Parable of the Talents av Octavia E. Butler, Neil Blomkamps film Elysium och Naughty Dogs datorspel The Last of Us och The Last of Us: Part II. Komparativ analys av motivet i de primära berättelserna ger vid handen hur katastrofer förvärrar den säkerhet och segregation som samhälls- formen möjliggör, vilket resulterar i en uttalad syn på personer utanför samhällena som Andra. Uppsatsen slår fast att gränserna för de spekulativa grindsamhällena sym- boliserar gränserna mellan det globala nord och syd, vilket retoriskt och fysiskt ute- stänger migranter från syd och konstruerar dem som Andra. Eftersom de flesta grindsamhällen i berättelserna drabbas av katastrof och kollaps på grund av de människor som man vägrar släppa in tycks texterna varna oss för att vi kan förvänta oss något liknande om den globala norden inte ser till att hantera frågor om klimaträttvisa idag. Octavia E. Butler The Parable of the Sower The Parable of the Talents Naughty Dog The Last of Us The Last of Us: Part II Neil Blomkamp Elysium ecocriticism post-apocalypse critical dystopia climate change criticism gated community urban studies agency the Other video game studies ergodic literature. Octavia E. Butler The Parable of the Sower The Parable of the Talents Naughty Dog The Last of Us The Last of Us: Part II Neil Blomkamp Elysium ekokritik postapokalyps kritisk dystopi klimatfiktion grindsamhällen urbana studier agens det Andra spelforskning ergodisk litteratur. Specific Literatures Litteraturstudier

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