1,720,973 research outputs found
A vibrotactile bracelet to improve the navigation of older adults in large and crowded environments
No full textThe decline of the cognitive abilities related to age usually determines a gradual withdrawal of older adults within the domestic walls. Part of the problem is the difficulty in navigating in large and crowded environments thatmay be perceived as intimidating. To alleviate this problem, we propose a vibrotactile device which can be used along with a walking assistant endowed with autonomous sensing and active brakes able to guide the user. In this paper, we address the problem of guiding the user with a minimal impact on his/her freedom of motion. We propose a solution based on the use of vibrotactile feedback to display directional cues. Psychophysical tests performed on a group of older adults show the effectiveness of the proposed vibrotactile strategy for the navigation of elderly people
Haptic wrist guidance using vibrations for Human-Robot teams
Full text linkHuman-Robot teams can efficiently operate in
several scenarios including Urban Search and Rescue (USAR).
Robots can access areas too small or deep for a person, can
begin surveying larger areas that people are not permitted to
enter and can carry sensors and instruments. One important
aspect in this cooperative framework is the way robots and
humans can communicate during rescue operation. Vision and
audio modalities may result not efficient in case of reduced
visibility or high noise. A promising way to guarantee effective
communications between robot and human in a team is the
exploitation of haptic signals. In this work, we present a possible
solution to let a robot guide the position of a human operator’s
hand by using vibrations. We demonstrate that an armband
embedding four vibrating motors is enough to guide the wrist
of an operator along a predefined path or in a target location.
The results proposed can be exploited in human-robot teams.
For instance, when the robot detects the position of a sensible
target, it can guide the wrist of the operator in such position
following an optimal path
Evaluation of a predictive approach in steering the human locomotion via haptic feedback
Full text linkIn this paper, we present a haptic guidance policy
to steer the user along predefined paths, and we evaluate
a predictive approach to compensate actuation delays that
humans have when they are guided along a given trajectory
via sensory stimuli. The proposed navigation policy exploits
the nonholonomic nature of human locomotion in goal directed
paths, which leads to a very simple guidance mechanism.
The proposed method has been evaluated in a real scenario
where seven human subjects were asked to walk along a set of
predefined paths, and were guided via vibrotactile cues. Their
poses as well as the related distances from the path have been
recorded using an accurate optical tracking system. Results
revealed that an average error of 0.24 m is achieved by using
the proposed haptic policy, and that the predictive approach
does not bring significant improvements to the path following
problem for what concerns the distance error. On the contrary,
the predictive approach achieved a definitely lower activation
time of the haptic interfaces
Haptic Guidance in Dynamic Environments Using Optimal Reciprocal Collision Avoidance
Full text linkHuman guidance in situations where the users cannot rely on their main sensory modalities, such as assistive or search-and-rescue scenarios, is a challenging task. In this letter, we address the problem of guiding users along collision-free paths in dynamic environments, assuming that they cannot rely on their main sensory modalities. In order to safely guide the subjects, we adapt the optimal reciprocal collision avoidance to our specific problem. The proposed algorithm takes into account the stimuli which can be displayed to the users and the motion uncertainty of the users when reacting to the provided stimuli. The proposed algorithm was evaluated in three different dynamic scenarios. A total of 18 blindfolded human subjects were asked to follow haptic cues in order to reach a target area while avoiding real static obstacles and moving users. Three metrics such as time to reach the goal, length of the trajectories, and minimal distance from the obstacles are considered to compare results obtained using this approach and experiments performed without visual impairments. Experimental results reveal that blindfolded subjects are successfully able to avoid collisions and safely reach the targets in all the performed trials. Although in this letter we display directional cues via haptic stimuli, we believe that the proposed approach can be general and tuned to work with different haptic interfaces and/or feedback modalities
PVA/STMP based hydrogels as potential substitutes of human vitreous
No full textPVA based hydrogels were synthesised using, as crosslinking agent, trisodium trimetaphosphate (STMP) to obtain potential substitutes for the vitreous body of the eye. The hydrogels, obtained using different amounts of STMP, were characterised by Infrared Spectroscopy which confirmed the successful occurrence of crosslinking reaction. The mechanical spectra of the fully hydrated samples confirmed covalently crosslinked systems (i.e. G’>G”). The rheological analysis pointed out that only one of the hydrogels (PVA STMP 8:1) showed a behaviour similar to that of human vitreous. The hydrogel was also subjected to injection through a small needle, a procedure that is essential in the use of vitreous substitutes. Further analysis in terms of light transmittance, water content measurements, diffusion coefficient and cytotoxicity confirmed the applicability of such a hydrogel as vitreous substitute
ToF-SIMS investigation of ancient ceramics from the Quartaia Site, Tuscany (Italy)
No full textThe study of ancient ceramic fragments provides important information about the production technology that characterized a certain civilization. In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS), atomic absorption spectroscopy(AAS) and scanning electron microscopy (SEM) were used to study two types of ceramics having different impasto (depurata and non-depurata ceramics). Ancient fragments, belonging to the archeological site of Quartaia (Tuscany, Italy), were examined to obtain chemical and spatial information on inorganic and organic components. The results revealed the presence of the major elements, i.e. Al, Mg, Na, K, Ca, Si, Fe; minor elements, i.e. Cr, Cu, Mn, Pb; and organic components adsorbed during the firing process, both in depurata and non-depurata ceramics. In addition, through ToF-SIMS imaging, it was possible to highlight inorganic components, i.e. Na, Ca, Fe, K and Mg, that showed an inhomogeneous spatial distribution in non-depurata ceramics. These chemical elements appear to be concentrated inside the inclusions of the non-depurata ceramics impasto. These unique results demonstrated that ToF-SIMS is a potential tool to reveal important aspects of the Quartaia ceramic production technology and it results in a very promising technique for the archeological studies
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
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