1,721,547 research outputs found
On inverse-direct systems of modules
No full textInverse-direct systems of modules have been considered by Eklof and Mekler. The systems we are going to study are different: we do not assume the condition that certain composite maps are identity maps. In this paper inverse-direct systems will be considered where certain composite maps lie in the center of the respective
endomorphism rings. We investigate how the limits are modified if the connecting maps are changed by automorphisms of the modules. It will also be shown that one can define a composition between the systems modified by these automorphisms such that those whose limits are non-isomorphic under the canonical maps form an abelian group. This group can be described in terms of the first derived functor of the inverse limit functor. We also study the relation to vanishing inverse limits: in certain cases, the maps can be
modified in such a way that the inverse limit of the new system becomes 0. In the final section, we use self-idealizations in order to construct sets of non-isomorphic modules (over suitable uncountable rings) that are direct limits of the same collection of modules with different connecting maps
Imagery in gymnastics: Theories and empirical findings
No full textSimonsmeier B, Frank C. Imagery in gymnastics: Theories and empirical findings. In: Heinen T, Cuk I, Goebel R, Velentzas K, eds. Gymnastics performance and motor learning. New York: NOVA; 2016: 53-69
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
The measurement of mental representations within the context of motor actions
No full textVelentzas K, Henning L, Jeraj D. The measurement of mental representations within the context of motor actions. In: Heinen T, Čuk I, Goebel R, Velentzas K, eds. Gymnastics Performance and Motor Learning – Principles and Applications. New York: Nova; 2016: 89-118
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Relationships between gaze behavior and motor behavior in complex aerial skills
No full textVelentzas K, Heinen T, Sato Y. Relationships between gaze behavior and motor behavior in complex aerial skills. In: Heinen T, Čuk I, Goebel R, Velentzas K, eds. Gymnastics Performance and Motor Learning – Principles and Applications. Sport and Athletics Preparation, Performance, and Psychology. NY: Nova; 2016
Almost Everywhere Conditions for Hybrid Lipschitz Lyapunov Functions
Full text linkWe introduce a class of locally Lipschitz continuous functions to establish stability of hybrid dynamical systems. Under certain regularity assumptions on system dynamics, we provide sufficient conditions for asymptotic stability on the candidate Lyapunov function. In contrast to the existing literature, these conditions need to be checked only on a dense set using the gradient of a certain function, without the necessity of relying on Clarke's generalized gradient. We discuss the relevance of the stated assumptions with the help of some counterexamples, underlining the subtlety of the proposed relaxation. As an application of our result, we study the stability of a classical example from the reset control literature: the Clegg integrator model, with convex and nonconvex Lyapunov functions, which are almost everywhere differentiable
Automated selection of brain regions for real-time fMRI brain-computer interfaces
No full textObjective. Brain-computer interfaces (BCIs) implemented with real-time functional magnetic resonance imaging (rt-fMRI) use fMRI time-courses from predefined regions of interest (ROIs). To reach best performances, localizer experiments and on-site expert supervision are required for ROI definition. To automate this step, we developed two unsupervised computational techniques based on the general linear model (GLM) and independent component analysis (ICA) of rt-fMRI data, and compared their performances on a communication BCI. Approach. 3 T fMRI data of six volunteers were re-analyzed in simulated real-time. During a localizer run, participants performed three mental tasks following visual cues. During two communication runs, a letter-spelling display guided the subjects to freely encode letters by performing one of the mental tasks with a specific timing. GLM- and ICA-based procedures were used to decode each letter, respectively using compact ROIs and whole-brain distributed spatio-temporal patterns of fMRI activity, automatically defined from subject-specific or group-level maps. Main results. Letter-decoding performances were comparable to supervised methods. In combination with a similarity-based criterion, GLM- and ICA-based approaches successfully decoded more than 80% (average) of the letters. Subject-specific maps yielded optimal performances. Significance. Automated solutions for ROI selection may help accelerating the translation of rt-fMRI BCIs from research to clinical applications
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