1,720,980 research outputs found
Development of a low cost eye gaze tracker
No full textEye gaze tracker is a device for monitoring and recording eye motion and related eye data. It is a hands-off, not intrusive, remote human-computer interface that can be used to track a user's gazepoint. It allows an operator to interact with their environment using only their eyes. During 2 decades of development, hundreds of eyegaze, eye-controlled, computer/communication systems have been sold around the world, primarily as an assistive device for people with disabilities and as a tool for human factors research. Gaze information plays an important role in identifying a person's focus of attention. The information can provide useful communication cues to a multimodal interface. A person's gaze direction is determined by two factors: the orientation of the head, and the orientation of the eyes. While the orientation of the head determines the overall direction of the gaze, the orientation of the eyes determines the exact gaze direction and is limited by the head orientation. To be applied in general computer interfaces, an ideal eye tracker should: be precise to minutes of arc; have repetitive behaviour; work under different conditions such as lighting fluctuations, operator with glasses and contact etc; allow for free head motion; be easy to use on a variety of subjects. This paper regards the development of an economic and ergonomic eye gaze tracker using time compression techniques. A low cost and custom fit approach is used in the development of this Eye gaze tracker: a single low-cost B/W mini-camera (Table 1) is used to acquire video images. A good image contrast is obtained using one IR LED, positioned in proximity of the camera, with orientation suitable to produce the dark-pupil effect: this setup allows an easy pupil image identification. The device shape is designed on a head virtual model obtained from the digitalization of a physical pattern; the point cloud of the head physical model is acquired using a laser scanner. The functional prototypes are produced using the fused deposition modelling (ABS) and selective laser sintering techniques(aluminium/polyammide). Fifty users (students) tested the functional prototypes, complete of all components to evaluate the functional and ergonomic device characteristics. The final cost of the prototype obtained is about 10% of the cost of the product available in the market
Accuracy of down-facing surfaces in complex internal channels produced by laser powder bed fusion (L-PBF)
Full text linkAdditive manufacturing (AM) technology has great potential in manufacturing complex internal channels for several applications such as satellite communication systems, electronics and gas turbine airfoils. These applications can have complex shape and make traditional finishing processes a challenge for additive parts. Therefore, it is desirable that the internal surfaces be as close as possible to the tolerance of the field of application. In this study, a complex component was designed and manufactured in AlSi10Mg alloy through laser powder bed fusion (L-PBF) process. Using the data from the 3D scans, internal surface roughness and deviations from the CAD model were calculated
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
Effect of track geometry on the measurement uncertainty of wear in pin-on-disc tribological test
No full textWear is connected to friction and hence affects energy efficiency and the environmental footprint of the process. The precise evaluation of wear damage will gain further relevance because it is a core input for developing prediction models of mechanical behaviour of materials, to be applied in the design stage of components and systems, and in the optimisation of new manufacturing processes and innovative materials, within the framework of Industry 4.0 and circular economy. Given the complexity of wear phenomenon, simplified wear tests are required; amongst these, pin-on-disc is a widespread test. It consists in sliding a pin against a disc either according to a circular path or along a linear alternate motion, to generate a track, whose volume is the characterisation target. Its characterisation standards rely upon gravimetric and volumetric method, which have several limitations, though. The former is inadequate for low-wear application and multi-material and multi-phase components, due to the difficulty in locally estimating material density. The latter, requiring profilometric measurements, does not suffer from these limitations; however, profilometric measurements are superseded by high-resolution and information-rich inspection techniques based on surface topography measurement, with respect to whom are less robust and representative. The profilometric method relies on a-priory defined track geometry; despite it is largely exploited, the effect of this approximation is unreported within a rigorous metrological framework. This work aims at assessing the effect of the track geometry on the accuracy and precision of the volumetric method, both according to standardised and surface topography approaches, within the current standards for topography measuring instruments based on metrological characteristics. This provides insights in the performance comparison of standard and non-standard volumetric methods in quantifying wear in pin-on-disc testing. The results will support the standardisation of topography-based method by providing users with confidence in their use and establishing traceability for this tribological test
Benchmarking analysis of digital light processing resins in terms of dimensional accuracy and geometric tolerances
Full text linkAdditive Manufacturing (AM) is a groundbreaking fabrication technology that is revolutionizing traditional manufacturing processes. Generally, following a layer-by-layer approach, in AM the final shape of the product is built through the progressive deposition of one or more materials. The most common extrusion-based AM technique for thermoplastic polymers is Fused Filament Fabrication (FFF), whilst for photopolymer resins, Digital Light Processing (DLP) and Stereolithography (SLA) are widely used. In the last years, DLP has spread rapidly, due to its low average cost and simple use. Moreover, a lower layer thickness can be used in DLP if compared to the FFF process. Therefore, hobbyists or amateur end users and many companies use DLP to achieve high dimensional accuracy and smooth surfaces for small products.
This work aims to evaluate the performance of three different DLP resins in terms of dimensional and geometrical accuracy. A benchmarking activity is carried out using a Rover printer by Sharebot to produce replicas of a reference part using Sharebot resins. After production, the replicas were inspected using a Coordinate Measuring Machine (CMM) for comparing the dimensional accuracy of the geometric features according to ISO IT grades and tolerances of the GD&T system. The results of this study are also compared with previous works from the literature in the conclusions
Build orientation effect on Ti6Al4V thin-wall topography by electron beam powder bed fusion
Full text linkAdditive Manufacturing is a key enabling technology for Industry 4.0 and the Green Deal, allowing more efficient resources exploitation while providing innovative design to critical components. Electron Beam Powder Bed Fusion (EB-PBF) is an edge technology for many sectors, i.e. aerospace, medical, and automotive. The control of the surface finish by surface topography measurements is essential to engineer surface functional properties, whose specifications are application specific. This works investigates the effect of thin-wall orientation and surface inclination on the topography, described by areal field and feature parameters, to provide designers with a useful tool in the early stage of product development and tolerance specification and verificatio
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
A methodology for evaluating the aesthetic quality of 3D printed parts
Full text linkNowadays, 3D printing is recognized as one of the key technologies that enables the distributed manufacturing adoption. However, inexperienced people might perceive this technology as far from easy user-usability because of evident aesthetic defects on 3D printed parts. In this paper, an indicator-based methodology is proposed for the assessment and the ranking of the aesthetic capability of 3D printers by evaluating the ability of a 3D printer to reproduce a reference part without defects. The reference part includes several geometric features that characterize most of as-built aesthetic defects. In addition, a benchmarking analysis was carried out to show an example of the methodology applied to three different machines
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