104 research outputs found
Knowledge-informed neuro-integrators for aggregation kinetics
We report a novel approach for the efficient computation of solutions of a broad class of large-scale systems of non-linear ordinary differential equations, describing aggregation kinetics. The method is based on a new take on the dimensionality reduction for this class of equations which can be naturally implemented by a cascade of small feed-forward artificial neural networks. We show that this cascade, of otherwise static models, is capable of predicting solutions of the original large-scale system over large intervals of time, using the information about the solution computed over much smaller intervals. The computational cost of the method depends very mildly on the temporalhorizon, which is a major improvement over the current state-of-the-art methods, whose complexity increases super-linearly with the systemâs size and proportionally to the simulation time. In cases when prior information about the values of solutions over a relatively small interval of time is already available, the methodâs computational complexity does not depend explicitly on the systemâs size. The successful application of the new method is illustrated for spatially-homogeneous systems, with a source of monomers, for a number of the most representative reaction rates kernels
Parametric Syntactic Reconstruction. Noun Phrases in Iranian, Proto-Indo-Iranian and Proto-Indo-European
This dissertation is a defense of the hypothesis that syntax can be reconstructed using the time-tested Comparative Method and structural analogues to phonological
features, so-called parameters.
Any application of the Comparative Method depends on a systematic comparison of basic units which are finite in number and have discrete values. This dissertation argues that syntactic parameters might equal distinctive phonological features and that different combinations or rather bundles of parameters might constitute syntactic âphonemesâ. Building upon the noun phrase (NP) properties and behavior of nine Old and Middle Iranian languages, namely Old and Young Avestan, Old and Middle Persian, Parthian, Bactrian, Chorasmian, Sogdian and Khotanese Saka as well as the corresponding NP characteristics of three ancient Indo-European relatives, namely Vedic, Archaic (i.e., Mycenaean and Epic) Greek and Old Latin, this study tries to reconstruct, based on a parametric feature matrix, (a) the nominal syntactic behavior (formally representable
in terms of parametric settings) of the last common ancestor of all Iranian languages, Proto-Iranian, (b) the parametric profile of the still earlier Proto-Indo-Iranian (PIIr.) language, and it makes (c) an educated first guess on the NP parameters of Proto-Indo-European (PIE).
Key findings of this dissertation are (I) the insight that parametric syntactic reconstruction parallels phonological reconstruction(s); (II) the observation that PIIr. and PIE had a right-branching nominal configurational syntax with a high amount of noun-raising (no rigid head-finality); (III) the inference that the non-IE substrate language(s) of the early towns of Bronze Age Central Asia (BMAC and related cultures) may have had articles
Modeling, analysis and control of robot-object nonsmooth underactuated Lagrangian systems: A tutorial overview and perspectives
International audienceSo-called robot-object Lagrangian systems consist of a class of nonsmooth underactuated complementarity Lagrangian systems, with a specific structure: an "object" and a "robot". Only the robot is actuated. The object dynamics can thus be controlled only through the action of the contact Lagrange multipliers, which represent the interaction forces between the robot and the object. Juggling, walking, running, hopping machines, robotic systems that manipulate objects, tapping, pushing systems, kinematic chains with joint clearance, crawling, climbing robots, some cable-driven manipulators, and some circuits with set-valued nonsmooth components, belong this class. This article aims at presenting their main features, then many application examples which belong to the robot-object class, then reviewing the main tools and control strategies which have been proposed in the Automatic Control and in the Robotics literature. Some comments and open issues conclude the article
Methods in Contemporary Linguistics
The present volume is a broad overview of methods and methodologies in linguistics, illustrated with examples from concrete research. It collects insights gained from a broad range of linguistic sub-disciplines, ranging from core disciplines to topics in cross-linguistic and language-internal diversity or to contributions towards language, space and society. Given its critical and innovative nature, the volume is a valuable source for students and researchers of a broad range of linguistic interests
Reconstructing Syntax
Contributing to the vigorous discussion of the viability of syntactic reconstruction, this volume offers methods for identifying i) cognates in syntax, and ii) the directionality of syntactic change, thus providing historical syntacticians with evidence that syntactic reconstruction is indeed both theoretically and practically feasible.; Readership: This volume is of interest to all historical syntacticians and historial linguists, as well as to specialists within Indo-European, Semitic, Austronesian and native American languages
Discriminative Video Representation Learning
Representation learning is a fundamental research problem in the area of machine learning, refining the raw data to discover representations needed for various applications. However, real-world data, particularly video data, is neither mathematically nor computationally convenient to process due to its semantic redundancy and complexity. Video data, as opposed to images, includes temporal correlation and motion dynamics, but the ground truth label is normally limited to category labels, which makes the video representation learning a challenging problem. To this end, this thesis addresses the problem of video representation learning, specifically discriminative video representation learning, which focuses on capturing useful data distributions and reliable feature representations improving the performance of varied downstream tasks. We argue that neither all frames in one video nor all dimensions in one feature vector are useful and should be equally treated for video representation learning. Based on this argument, several novel algorithms are investigated in this thesis under multiple application scenarios, such as action recognition, action detection and one-class video anomaly detection. These proposed video representation learning methods produce discriminative video features in both deep and non-deep learning setups. Specifically, they are presented in the form of: 1) an early fusion layer that adopts a temporal ranking SVM formulation, agglomerating several optical flow images from consecutive frames into a novel compact representation, named as dynamic optical flow images; 2) an intermediate feature aggregation layer that applies weakly-supervised contrastive learning techniques, learning discriminative video representations via contrasting positive and negative samples from a sequence; 3) a new formulation for one-class feature learning that learns a set of discriminative subspaces with orthonormal hyperplanes to flexibly bound the one-class data distribution using Riemannian optimisation methods. We provide extensive experiments to gain intuitions into why the learned representations are discriminative and useful. All the proposed methods in this thesis are evaluated on standard publicly available benchmarks, demonstrating state-of-the-art performance
Crisis and Individuation: Mapping and Navigating the Planetary Crisis Convergence
We live in an era of converging global crises, from climate change and mass extinction to political-economic turbulence, energy depletion, food crises, and emerging technological risks. But how will these crises combine and feedback on each other? How might they unfold over the coming years and decades? And what can be done to solve or at least navigate these crises? This dissertation argues that answers to these questions have been hindered by limited efforts so far, both in the field of International Relations and beyond, to develop more holistic analyses of these crises. In large part this is due to the dominance of âisolationistâ approaches to the study of global crisis and the social sciences more generally: the tendency to analytically isolate specific systems and problems from other systems with which theyâre connected. While isolationist analyses are vital, I argue that they must be supplemented with multidimensional and synthetic analyses in order to adequately grasp the complexity of the contemporary planetary crisis, or what I call the âplanetary crisis convergenceâ, and understand how it may unfold in the coming decades. Overall, this dissertation presents two core arguments. First, that the contemporary world system is on the cusp of a catastrophic discontinuity that will irreversibly transform livelihoods, states, and world order over the next two to four decades. Second, that to see this imminent rupture, understand its causal drivers, and map its possible future trajectories requires a multi-dimensional systems theoretical approach that encompasses political-economic, technological, geological, and ecological processes. To pursue this analysis I develop a theoretical framework drawing from complexity theory, Marxist political economy, and the philosophy of Gilles Deleuze alongside natural scientific studies on climate change, food and energy systems, and technological change. In this way the dissertation synthesizes quantitative analyses of key trends in climate, food, and energy systems with qualitative analysis of political economy, technology, power, and resistance in order to illuminate the possible trajectories of the planetary crisis convergence and inform counter-hegemonic responses. It concludes that these crises will most likely force a transition in the world-system towards one of three global-scale scenarios: a Techno-Authoritarian Planetary Leviathan, an Ecosocialist world-system, or a global collapse. It proposes that a democratic ecosocialist world-system is needed to respond to the planetary crisis convergence in a genuinely sustainable and just manner, which would involve a new political-economy based on well-being, post-growth principles, and democratic planning at multiple scales
Placing problems from phylogenetics and (quantified) propositional logic in the polynomial hierarchy
In this thesis, we consider the complexity of decision problems from two different areas of research and place them in the polynomial hierarchy: phylogenetics and (quantified) propositional logic. In phylogenetics, researchers study the evolutionary relationships between species. The evolution of a particular gene can often be represented by a single phylogenetic tree. However, in order to model non-tree-like events on a species level such as hybridization and lateral gene transfer, phylogenetic networks are used. They can be considered as a structure that embeds a whole set of phylogenetic trees which is called the display set of the network. There are many interesting questions revolving around display sets and one is often interested in the computational complexity of the considered problems for particular classes of networks. In this thesis, we present our results for different questions related to the display sets of two networks and place the corresponding decision problems in the polynomial hierarchy. Another interesting question concerns the reconstruction of networks: given a set T of phylogenetic trees, can we construct a phylogenetic network with certain properties that embeds all trees in T? For a class of networks that satisfies certain temporal properties, Humphries et al. (2013) established a characterization for when this is possible based on the existence of a particular structure for T, a so-called cherry-picking sequence. We obtain several complexity results for the existence of such a sequence: Deciding the existence of a cherry-picking sequence turns out to be NP-complete for each non-trivial number (i.e., at least two) of given trees. Thereby, we settle the open question stated by Humphries et al. (2013) on the complexity for the case |T| = 2. On the positive side, we identify a special case that we place in the complexity class P by exploring connections to automata theory. Regarding propositional logic, we present our complexity results for the classical satisfiability problem (and variants resp. quantified generalizations thereof) and place the considered variants in the polynomial hierarchy. A common theme is to consider bounded variable appearances in combination with other restrictions such as monotonicity of the clauses or planarity of the incidence graph. This research was inspired by the conjecture that Monotone 3-SAT remains NP-complete if each variable appears at most five times which was stated in the scribe notes of a lecture held by Erik Demaine; we confirm this conjecture in an even more restricted setting where each variable appears exactly four times
Automatic Loanword Identification Using Tree Reconciliation
Die Verwendung von computerbasierten Methoden in der Historischen Linguistik stieg in den letzten Jahren stetig an. Phylogenetische Methoden, welche zur Bestimmung der Evolutionsgeschichte und Verwandtschaftsgraden zwischen Organismen entwickelt wurden, erhielten Einzug in die Historische Linguistik. Die VerfĂŒgbarkeit von maschinenlesbaren Daten förderten deren Anpassung und Weiterentwicklung. WĂ€hrend einige Algorithmen zur Rekonstruktion der sprachlichen Evolutionsgeschichte ĂŒbernommen wurden, wurde den Methoden fĂŒr horizontalen Transfer kaum Beachtung geschenkt. Angelehnt an die Parallele zwischen horizontalem Gentransfer und Entlehnung, werden in dieser Arbeit phylogenetische Methoden zur Erkennung von horizontalem Gentransfer fĂŒr die Identifikation von Lehnwörtern verwendet.
Die Algorithmen fĂŒr horizontalen Gentransfer basieren auf dem Vergleich zweier phylogenetischer BĂ€ume. In der Linguistik bildet der Sprachbaum die Sprachgeschichte ab, wĂ€hrend ein Konzeptbaum die Evolutionsgeschichte einzelner Wörter reprĂ€sentiert. Die Rekonstruktion eines Sprachbaumes ist wissenschaftlich fundiert, wohingegen die Rekonstruktion von KonzeptbĂ€umen bisher wenig erforscht wurde. Eine erhebliche Innovation dieser Arbeit ist die EinfĂŒhrung verschiedener Methoden zur Rekonstruktion von stabilen KonzeptbĂ€umen. Da die Algorithmen zur Erkennung von horizontalem Transfer auf einem Baumvergleich basieren, deuten die Unterschiede zwischen einem Sprachbaum und einem Konzeptbaum auf Lehnwörter innerhalb der Daten hin. Daher wird sowohl die Methodik, als auch ein geeigneter Algorithmus in einem linguistischen Kontext eingefĂŒhrt. Die Ergebnisse der Lehnworterkennung werden mithilfe eines neu entwickelten Goldstandards evaluiert und mit drei weiteren Algorithmen aus der Historischen Computerlinguistik verglichen. Ziel der Arbeit ist zu erlĂ€utern, inwieweit Algorithmen basierend auf dem Vergleich zweier BĂ€ume fĂŒr die automatische Lehnworterkennung verwendet und in welchem Umfang Lehnwörter erfolgreich innerhalb der Daten bestimmt werden können. Die Identifikation von Lehnwörtern trĂ€gt zu einem tieferen VerstĂ€ndnis von Sprachkontakt und den unterschiedlichen Arten von Lehnwörtern bei. Daher ist die Adaption von phylogenetischen Methoden nicht nur lohnenswert fĂŒr die Bestimmungen von Entlehnungen, sondern dient auch als Basis fĂŒr weitere, detailliertere Analysen auf den Gebieten der automatischen Lehnworterkennung und Kontaktlinguistik.The use of computational methods in historical linguistics increased during the last years. Phylogenetic methods, which explore the evolutionary history and relationships among organisms, found their way into historical linguistics. The availability of machine-readable data accelerated their adaptation and development. While some methods addressing the evolution of languages are integrated into linguistics, scarcely any attention has been paid to methods analyzing horizontal transmission. Inspired by the parallel between horizontal gene transfer and borrowing, this thesis aims at adapting horizontal transfer methods into computational historical linguistics to identify borrowing scenarios along with the transferred loanwords.
Computational methods modeling horizontal transfer are based on the framework of tree reconciliation. The methods attempt to detect horizontal transfer by fitting the evolutionary history of words to the evolution of their corresponding languages, both represented in phylogenetic trees. The discordance between the two evolutionary scenarios indicates the influence of loanwords due to language contact. The tree reconciliation framework is introduced in a linguistic setting along with an appropriate algorithm, which is applied to linguistic trees to detect loanwords. While the reconstruction of language trees is scientifically substantiated, little research has so far be done on the reconstruction of concept trees, representing the wordsâ histories. One major innovation of this thesis is the introduction of various methods to reconstruct reliable concept trees and determine their stability in order to achieve reasonable results in terms of loanword detection. The results of the tree reconciliation are evaluated against a newly developed gold standard and compared to three methods established for the task of language contact detection in computational historical linguistics.
The main aim of this thesis is to clarify the purpose of tree reconciliation methods in linguistics. The following analyses should give insights to which degree the direct transfer of phylogenetic methods into the field of linguistics is fruitful and can be used to discover borrowings along with the transferred loanwords. The identification of loanwords is a first step into the direction of a deeper understanding of contact scenarios and possible types of loanwords present in linguistic data. The adaptation of phylogenetic methods is not only worthwhile to shed light on detailed horizontal transmissions, but serves as basis for further, more detailed analyses in the field of contact linguistics
- âŠ