1,720,955 research outputs found
Brain-Computer Interfaces based on multisensory Event-Related Potentials
No full textThis dissertation is organized along the four research questions in the form of scientific papers. We here give an overview of each chapter, their motivations, and the relation between them. Chapter 2: Controlling a tactile ERP-BCI in a dual-task. In this chapter we present the evaluation of what the costs of mental resources are to control a tactile ERP-BCI while at the same time performing a concurrent task using visual information. This is the first step towards applying a tactile ERP-BCI for navigation. For tasks like (serious) gaming cognitive resources are required, but when operating an ERP-BCI attending to stimuli also demands (cognitive) resources. We investigate whether or not these two tasks can be performed simultaneously, and what the effects on brain signals (and subsequently BCI performance) and task performance are. Chapter 3: Does bimodal stimulus presentation increase ERP components usable in BCIs? In this chapter we report the idea to increase ERP activity by means of bimodal (visual-tactile) stimulus presentation, with the goal to enhance BCI performance. Bimodal stimuli could evoke additional brain activity due to multisensory integration which may be of use in a BCI. We investigate effects of attending to bimodal visual-tactile (compared to unimodal) stimuli on the ERP. To this end we use stimulus pairs of tactile stimuli around the waist and visual stimuli embedded in a navigation environment presented on a display, corresponding in navigation direction. Chapter 4: Bimodal location-congruent ERP-BCIs: Increasing gaze-independent performance. In this chapter we further investigate bimodal (visual-tactile) ERP-BCIs and the role of location-congruency of the bimodal stimulus. Research has shown that bimodal stimuli do not necessarily have to be location-congruent to observe positive bimodal effects on task performance and brain activity, yet location-congruent bimodal stimuli may (further) positively affect task performance and ERP components. Whereas in chapter 3 we use a gaze-dependent setup as a first step and to compare results to traditional BCIs, in chapter 4 we take the next step by using a gaze-independent setup. In the latter case, the potential benefits of bimodal stimuli are expected to be greater as gaze-independent BCI performance is typically relatively low. Additionally, we study the effect of selectively attending to a modality in bimodal BCIs. Chapter 5: Control-display mapping in brain–computer interfaces. In this chapter we present our research on the effect of congruency regarding the relation between command options and stimuli in a BCI-context. When using a tactile ERP-BCI for navigation, mapping is required between navigation directions on a visual display and unambiguously corresponding tactile stimuli from a tactile control device: control-display mapping (CDM). Chapter 6: Discussion and conclusions. We discuss the results of the separate studies and integrate the studies to answer the main research question. Furthermore, we discuss the implications of our results, reflect on the usefulness of ERP-BCI for direct control and for other purposes, and make recommendations for future research. We finalise with some concluding remarks
Animating virtual characters using physics-based simulation
No full textOver the past decades, physics-based simulation has become an established method for the animation of passive phenomena, such as cloth, water and rag-doll characters. The conception that physics-based simulation can also be used for animating actively controlled characters dates back to the early stages of computer animation, and has incited many research papers since. However, commercial animation frameworks still resort to kinematics-based approaches when it comes to animating active virtual characters. To understand this reservation, it is important to recognize the scope and complexity of controlling simulated characters. Just like with real-world characters, the pose of a physics-based character is controlled indirectly, through forces and torques generated by actuators that reside inside the body. As a result, the global position and orientation of a physics-based character cannot be controlled directly, but only through deliberate manipulation of external contacts. This poses a direct challenge to basic tasks such as balance and locomotion – a challenge that has no equivalent in traditional kinematics-based animation. Instead, it bears a much closer relation to humanoid robotics and control theory. In addition to these control challenges, physics-based virtual characters should also behave in a way that is visually appealing. In order to look natural, the motion of a character must respect the same biological constraints that are present in natural beings. Recently, researchers have begun incorporating such constraints into their character models, based on results from biomechanics research. This trend is gradually changing the direction of physics-based character animation research, and is further broadening its scope. To implement all these aspects into a robust and flexible framework has proven to be a daunting task. However, recent trends show a renewed interest in physics-based character animation. After decades of floundering, the field is maturing, with many recent publications demonstrating tremendous progress in both robustness and visual quality. As such, physics-based character animation remains an exciting research topic that is likely to play an increasingly important role in computer animation in the years to come. This thesis describes various elements involved in animating virtual characters using physics-based simulation. The first part contains a thorough review of several fundamental aspects of physics-based character animation, including modeling, simulation and control. The second part describes the results of research on how simulation and modeling techniques can be used for the assessment of different aspects of motion, without the use of a control strategy. The third part of this thesis describes two novel control methods for physics-based characters. The first method controls physics-based bipeds in a simulated environment, based on a variety of reference motions. The second method is a muscle-based control strategy for simulated bipeds, in which both the muscle routing and control parameters are optimized. This thesis concludes with a summary and an overview of possible directions for future research
Gaze-independent ERP-BCIs: augmenting performance through location-congruent bimodal stimuli
No full textGaze-independent event-related potential (ERP) based brain-computer interfaces (BCIs) yield relatively low BCI performance and traditionally employ unimodal stimuli. Bimodal ERP-BCIs may increase BCI performance due to multisensory integration or summation in the brain. An additional advantage of bimodal BCIs may be that the user can choose which modality or modalities to attend to. We studied bimodal, visual-tactile, gaze-independent BCIs and investigated whether or not ERP components’ tAUCs and subsequent classification accuracies are increased for (1) bimodal versus unimodal stimuli, (2) location-congruent versus location-incongruent bimodal stimuli, and (3) attending to both modalities versus to either one modality. We observed an enhanced bimodal (compared to unimodal) P300 tAUC, which appeared to be positively affected by location-congruency (p=.056) and resulted in higher classification accuracies. Attending either to one or to both modalities of the bimodal location-congruent stimuli resulted in differences between ERP components, but not in classification performance. We conclude that location-congruent bimodal stimuli improve ERP-BCIs, and offer the user the possibility to switch the attended modality without losing performance
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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