4,408 research outputs found

    Active-passive dynamic consensus filters: Theory and applications

    Get PDF
    ”This dissertation presents a new method for distributively sensing dynamic environments utilizing integral action based system theoretic distributed information fusion methods. Specifically, the main contribution is a new class of dynamic consensus filters, termed active-passive dynamic consensus filters, in which agents are considered to be active, if they are able to sense an exogenous quantity of interest and are considered to be passive, otherwise, where the objective is to drive the states of all agents to the convex hull spanned by the exogenous inputs sensed by active agents. Additionally, we generalize these results to allow agents to locally set their value-of-information, characterizing an agents ability to sense a local quantity of interest, which may change with respect to time. The presented active-passive dynamic consensus filters utilize equations of motion in order to diffuse information across the network, requiring continuous information exchange and requiring agents to exchange their measurement and integral action states. Additionally, agents are assumed to be modeled as having single integrator dynamics. Motivated from this standpoint, we utilize the ideas and results from event-triggering control theory to develop a network of agents which only share their measurement state information as required based on errors exceeding a user-defined threshold. We also develop a static output-feedback controller which drives the outputs of a network of agents with general linear time-invariant dynamics to the average of a set of applied exogenous inputs. Finally, we also present a system state emulator based adaptive controller to guarantee that agents will reach a consensus even in the presence of input disturbances. For each proposed active-passive dynamic consensus filter, a rigorous analysis of the closed-loop system dynamics is performed to demonstrate stability. Finally, numerical examples and experimental studies are included to demonstrate the efficacy of the proposed information fusion filters”--Abstract, page iv

    Usage-based and emergentist approaches to language acquisition

    Get PDF
    It was long considered to be impossible to learn grammar based on linguistic experience alone. In the past decade, however, advances in usage-based linguistic theory, computational linguistics, and developmental psychology changed the view on this matter. So-called usage-based and emergentist approaches to language acquisition state that language can be learned from language use itself, by means of social skills like joint attention, and by means of powerful generalization mechanisms. This paper first summarizes the assumptions regarding the nature of linguistic representations and processing. Usage-based theories are nonmodular and nonreductionist, i.e., they emphasize the form-function relationships, and deal with all of language, not just selected levels of representations. Furthermore, storage and processing is considered to be analytic as well as holistic, such that there is a continuum between children's unanalyzed chunks and abstract units found in adult language. In the second part, the empirical evidence is reviewed. Children's linguistic competence is shown to be limited initially, and it is demonstrated how children can generalize knowledge based on direct and indirect positive evidence. It is argued that with these general learning mechanisms, the usage-based paradigm can be extended to multilingual language situations and to language acquisition under special circumstances

    Fictionalism of Anticipation

    Get PDF
    A promising recent approach for understanding complex phenomena is recognition of anticipatory behavior of living organisms and social organizations. The anticipatory, predictive action permits learning, novelty seeking, rich experiential existence. I argue that the established frameworks of anticipation, adaptation or learning imply overly passive roles of anticipatory agents, and that a fictionalist standpoint reflects the core of anticipatory behavior better than representational or future references. Cognizing beings enact not just their models of the world, but own make-believe existential agendas as well. Anticipators embody plausible scripts of living, and effectively assume neo-Kantian or pragmatist perspectives of cognition and action. It is instructive to see that anticipatory behavior is not without mundane or loathsome deficiencies. Appreciation of ferally fictionalist anticipation suggests an equivalence of semiosis and anticipation

    Corpus studies and localization: a research proposal for interactive material

    Get PDF
    This article aims to analyze the dubbing synchronies used in a multimodal corpus composed of three video games, dubbed into Castilian Spanish, belonging to the interactive genre of action-adventure. The methodology, adopting a descriptive approach, triangulates qualitative and quantitative data obtained, on the one hand, from the empirical analysis of the multimodal corpus and, on the other hand, from direct contact with professionals in the industry through semi-structured interviews. Additionally, some previous approaches within Corpus-Based Translation Studies—closely linked to Descriptive Translation Studies—will be reviewed, as well as the professional practice of localization, from the perspective of audiovisual translation (AVT). The goal is thus to present how different methods and perspectives can be combined to analyze the AVT mode of dubbing in a multimodal and interactive product, which remains largely unexplored in academia so far, despite the efficacy that corpus studies have demonstrated in translation studies.Este artículo pretende dar cuenta de las sincronías empleadas en el doblaje al español peninsular de un corpus multimodal compuesto por tres videojuegos del género interactivo de la acción-aventura. La metodología, de enfoque descriptivo, triangula datos cualitativos y cuantitativos obtenidos, por una parte, del análisis empírico del corpus multimodal y, por otra, del contacto directo con profesionales de la industria mediante entrevistas semiestructuradas. Asimismo, se revisarán algunos planteamientos previos de los estudios de corpus, estrechamente relacionados con los Estudios Descriptivos en Traducción, y de la práctica profesional de la localización, abordándola desde el enfoque de la Traducción Audiovisual (TAV). Se busca así exponer cómo combinar distintos métodos y perspectivas para analizar la modalidad de TAV del doblaje en un producto multimodal interactivo, aspecto escasamente investigado empíricamente en la esfera académica por el momento, a pesar de la utilidad que ya han demostrado los estudios de corpus en el panorama traductológico

    Quantitative test of the barrier nucleosome model for statistical positioning of nucleosomes up- and downstream of transcription start sites

    Get PDF
    The positions of nucleosomes in eukaryotic genomes determine which parts of the DNA sequence are readily accessible for regulatory proteins and which are not. Genome-wide maps of nucleosome positions have revealed a salient pattern around transcription start sites, involving a nucleosome-free region (NFR) flanked by a pronounced periodic pattern in the average nucleosome density. While the periodic pattern clearly reflects well-positioned nucleosomes, the positioning mechanism is less clear. A recent experimental study by Mavrich et al. argued that the pattern observed in S. cerevisiae is qualitatively consistent with a `barrier nucleosome model', in which the oscillatory pattern is created by the statistical positioning mechanism of Kornberg and Stryer. On the other hand, there is clear evidence for intrinsic sequence preferences of nucleosomes, and it is unclear to what extent these sequence preferences affect the observed pattern. To test the barrier nucleosome model, we quantitatively analyze yeast nucleosome positioning data both up- and downstream from NFRs. Our analysis is based on the Tonks model of statistical physics which quantifies the interplay between the excluded-volume interaction of nucleosomes and their positional entropy. We find that although the typical patterns on the two sides of the NFR are different, they are both quantitatively described by the same physical model, with the same parameters, but different boundary conditions. The inferred boundary conditions suggest that the first nucleosome downstream from the NFR (the +1 nucleosome) is typically directly positioned while the first nucleosome upstream is statistically positioned via a nucleosome-repelling DNA region. These boundary conditions, which can be locally encoded into the genome sequence, significantly shape the statistical distribution of nucleosomes over a range of up to ~1000 bp to each side.Comment: includes supporting materia

    THE OBVIATION HIERARCHY AND MORPHO SYNTACTIC MARKEDNESS

    Get PDF
    Numerous languages of the Americas display special syntax and/or morphology in clauses containing two 3rd person core arguments (and no 1st or 2nd person argument). Because the principles underlying these systems share important properties with the obviation systems of Algonquian languages, it is assumed here that they are all organized in terms of (abstract) OBVIATION. This paper develops some aspects of aformal account of obviation within the framework of Optimality Theory (OT), and provides one answer to the question, what is the role of hierarchies in grammar? The answer suggested here is that hierarchies (scales) are not themselves part of grammar, but they provide the raw material from which grammatical constraints are generated. Various aspects of the morphology and syntax of obviation systems are described here in terms of constraint subhierarchies which are derived from the OBVIATION SCALE alone, orfrom the alignment of the obviation scale with other relevant scales

    Distributed Kalman Filters over Wireless Sensor Networks: Data Fusion, Consensus, and Time-Varying Topologies

    Get PDF
    Kalman filtering is a widely used recursive algorithm for optimal state estimation of linear stochastic dynamic systems. The recent advances of wireless sensor networks (WSNs) provide the technology to monitor and control physical processes with a high degree of temporal and spatial granularity. Several important problems concerning Kalman filtering over WSNs are addressed in this dissertation. First we study data fusion Kalman filtering for discrete-time linear time-invariant (LTI) systems over WSNs, assuming the existence of a data fusion center that receives observations from distributed sensor nodes and estimates the state of the target system in the presence of data packet drops. We focus on the single sensor node case and show that the critical data arrival rate of the Bernoulli channel can be computed by solving a simple linear matrix inequality problem. Then a more general scenario is considered where multiple sensor nodes are employed. We derive the stationary Kalman filter that minimizes the average error variance under a TCP-like protocol. The stability margin is adopted to tackle the stability issue. Second we study distributed Kalman filtering for LTI systems over WSNs, where each sensor node is required to locally estimate the state in a collaborative manner with its neighbors in the presence of data packet drops. The stationary distributed Kalman filter (DKF) that minimizes the local average error variance is derived. Building on the stationary DKF, we propose Kalman consensus filter for the consensus of different local estimates. The upper bound for the consensus coefficient is computed to ensure the mean square stability of the error dynamics. Finally we focus on time-varying topology. The solution to state consensus control for discrete-time homogeneous multi-agent systems over deterministic time-varying feedback topology is provided, generalizing the existing results. Then we study distributed state estimation over WSNs with time-varying communication topology. Under the uniform observability, each sensor node can closely track the dynamic state by using only its own observation, plus information exchanged with its neighbors, and carrying out local computation
    corecore