Search results for "VISION"
showing 10 items of 5066 documents
Howard–Dolman stereovision test at different opponent colour stimuli
2011
The purpose of this study was to investigate visual depth perception of real physical colour stimuli with red-green and blue-yellow opponency. We modified the Howard–Dolman stereotest where subjects should determine the closer of two bars emitting the light of definite colour placed in front of a CRT monitor served as colour background. Two-alternative forced-choice paradigms were used to determine depth perception threshold values. Thresholds close to 5–10 arcsec for luminance and colour contrast stimuli were revealed both for red-green and blue-yellow stimuli. A term, stereosensitivity – a reciprocal magnitude of the stereothreshold – was introduced to separately analyse luminance and col…
Simple Configuration Effects on Eye Movements in Horizontal Scanning Tasks
2015
When reading text, observers alternate periods of stable gaze (fixations) and shifts of gaze (saccades). An important debate in the literature concerns the processes that drive the control of these eye movements. Past studies using strings of letters rather than meaningful text ('z-reading') suggest that eye movement control during reading is, to a large extent, controlled by low-level image properties. These studies, however, have failed to take into account perceptual grouping processes that could drive these low-level effects. We here study the role of various grouping factors in horizontal scanning eye movements, and compare these to reading meaningful text. The results show that sequen…
Spatio-temporal Contrast Sensitivity in the Cardinal Directions of the Colour Space. A Review
2010
AbstractWe review the psychophysics of the spatio-temporal contrast sensitivity in the cardinal directions of the colour space and their correlation with those neural characteristics of the visual system that limit the ability to perform contrast detection or pattern-resolution tasks. We focus our attention particularly on the influence of luminance level, spatial extent and spatial location of the stimuli - factors that determine the characteristics of the physiological mechanisms underlying detection. Optical factors do obviously play a role, but we will refer to them only briefly. Contrast sensitivity measurements are often used in clinical practice as a method to detect, at their early …
Multifokale Intraokularlinsen
2001
Modern cataract surgery has developed tremendously during the past 10-15 years. Improved surgical techniques, as well as improved implant materials and designs, have enlarged patient profiles and indications for cataract surgery. This also created much higher expectations from the patients' site. The loss of accommodation is loss of quality of life for presbyopic and especially young pseudophakic patients. Therefore cataract surgery with multifocal IOL implantation is not only of academic interest, but reflects demands and expectations of our patients. Multifocal IOLs have been implanted since 1986, starting with 2-3 zone refractive and diffractive designs. Due to surgical techniques of tha…
Binocular vision alterations after refractive and cataract surgery: a review.
2018
To review binocular and accommodative disorders documented after corneal or intraocular refractive surgery, in normal healthy prepresbyopic patients. A bibliographic revision was performed; it included works published before 1st July 2017 where accommodation and/or binocularity was assessed following any type of refractive surgical procedure. The search in Pubmed yielded 1273 papers, 95 of which fulfilled the inclusion criteria. Few publications reporting binocular vision and/or accommodative changes after refractive surgery in normal subjects were found. The reduction in fusional vergence is the most frequently reported alteration. Anisometropia is an important risk factor for postoperativ…
Parasitoids (Hymenoptera) of leaf-spinning moths (Lepidoptera) feeding on Vaccinium uliginosum L. along an ecological gradient in central European pe…
2011
Parasitoids of leaf-spinning Lepidoptera associated with two isolated central European peat bogs were investigated. Five families of parasitoid Hymenoptera (Braconidae, lchneumonidae, Eulophidae, Pteromalidae and Encyrtidae) were recorded. Three categories were recognised: (1) primary parasitoids, (2) facultative hyperparasitoids and (3) obligatory hyperparasitoids. Ten species of Braconidae, five species and seven marked morphospecies among lchneumonidae, and three species of Chalcidoidea were identified. Despite of some niche-specific (but less host-specific) parasitoids, all these hymenopterans are likely to be generalists and none of them were confirmed to be habitat and/or host special…
Early warning thresholds for partially saturated slopes in volcanic ashes
2013
Rainfall-induced landslides in steep soil slopes of volcanic origin are a major threat to human lives and infrastructure. In the context of constructing early warning systems in regions where extensive data on landslide occurrences and associated rainfall are inexistent, physically-based tools offer the possibility to establish thresholds for measurable field quantities. In this paper, a combined finite element infinite slope model is presented to study the transient hydraulic response of volcanic ash slopes to a series of rainfall events and to estimate seasonal safety factors. Furthermore, analytical considerations of partially saturated infinite slopes are made to define capillary stress…
On Augmented Reality for the Learning of 3D-Geometric Contents: A Preliminary Exploratory Study with 6-Grade Primary Students
2019
Nowadays, Augmented Reality (AR) is one of the emerging technologies with a greater impact in the Education field. Research has proved that AR-based activities improve the teaching and learning processes. Also, the use of this type of technology in classroom facilitates the understanding of contents from different areas as Arts, Mathematics or Science. In this work we propose an AR-based instruction in order to explore the benefits in a 6th-grade Primary course related to 3D-geometry shapes. This first experiment, designed from an exploratory approach, will shed light on new study variables to perform new implementations whose conclusions become more consistent. The results obtained allow u…
Fostering sustained teacher learning: a longitudinal assessment of the influence of vision building and goal interdependence on information sharing
2020
To support school improvement, understanding the mechanisms that enhance teachers’ engagement in professional learning activities within schools over time is paramount. The purpose of this three-wave longitudinal study is to examine the role of workplace conditions (school leaders’ vision building and teams’ shared goals), in supporting teachers’ engagement in information sharing over time. To test the directionality of the relationships between the concepts, we analyzed survey data from 655 vocational education and training teachers in the Netherlands using a cross-lagged panel model. Results suggest that teachers’ engagement in information sharing remains stable over time, and the results…
Contributions à la Vision par Ordinateur pour les Systèmes en Lumière Structurée et les Systèmes Catadioptriques
2008
Mes travaux de recherche concernent essentiellement la vision par ordinateur, ou vision artificielle. Basiquement, je me suis efforcé d'imaginer des dispositifs, d'étudier des algorithmes, d'intégrer des méthodes et techniques connues dans des méthodologies nouvelles, de développer çà et là des aspects théoriques originaux. Je me suis beaucoup intéressé à des systèmes de vision alternatifs comme les systèmes en lumière structurée ou catadioptriques. Ces systèmes permettent d'étudier les techniques usuelles de vision par ordinateur sous un éclairage différent, ils nous obligent à ajuster le problème aux caractéristiques qui leur sont propres ; ils permettent, en quelq…