1,721,009 research outputs found
FUEL CELL BASED-ON POWERTRAIN TO HYBRIDIZE SMALL UNMANNED AERIAL VEHICLES
No full textThe proposed investigation aims at increasing the
endurance of a small unmanned aerial vehicle (UAV) where the
power request for propulsion can be satisfied by means of a
battery and a fuel cell. The hybrid configuration allows the
required power to be obtained at take-off and the fuel cell to
support the battery in order to maintain the state of charge (SOC)
in the other phases of flight. This operating mode avoids deep
discharging, when the battery SOC falls down a suitable
threshold, and overcharging, which exposes to risk of explosion in
case of lithium batteries. The cost of adding different capacity
batteries was evaluated in terms of the increase of mass and
consequently decrease of endurance. The power split was
conveniently defined at take-off to prevent from excessive
hydrogen consumption and to maximize the endurance with
respect to the non-hybrid configuration in which the only fuel cell
is used
Il vescovo, il duca, l'angelo. Conflitti religiosi e dinamiche sociali a Catania dopo il terremoto del 1693
No full text
A smart robotic arm for automatic sorting of objects with different tags
No full textThis paper presents a mechatronics application to automatically sort objects with a robotic arm. The robotic arm picks similar objects and moves them in order to read the information contained in tags. In this way, the arm is able to place the objects in different final positions depending on the captured information. The starting position of a box is perceived by processing an image acquired by means of a webcam. The reading is made by using a Reader placed in a pre-fixed location inside the work space of the robotic arm. The movement of the robotic arm is guaranteed by an accurate kinematic model. The robotic arms are widely used in industry, but most of them are programmed to follow a previously learned trajectory. Very few robots are able to make real-time decisions and so they may not be considered smart systems. One example of smart robotic arm is provided by a device which can sort some objects taking advantage of the information contained in tags glued on the basis of the same objects. These systems can be used in several applications for protecting the environments aimed to automatize the processes of waste stocking and disposal simply differentiating the tag information
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
Unevenness point descriptor for terrain analysis in mobile robot applications
No full textIn recent years, the use of imaging sensors that produce a three-dimensional representation of the environment has become an efficient solution to increase the degree of perception of autonomous mobile robots. Accurate and dense 3D point clouds can be generated from traditional stereo systems and laser scanners or from the new generation of RGB-D cameras, representing a versatile, reliable and cost-effective solution that is rapidly gaining interest within the robotics community. For autonomous mobile robots, it is critical to assess the traversability of the surrounding environment, especially when driving across natural terrain. In this paper, a novel approach to detect traversable and non-traversable regions of the environment from a depth image is presented that could enhance mobility and safety through integration with localization, control and planning methods. The proposed algorithm is based on the analysis of the normal vector of a surface obtained through Principal Component Analysis and it leads to the definition of a novel, so defined, Unevenness Point Descriptor. Experimental results, obtained with vehicles operating in indoor and outdoor environments, are presented to validate this approach. © 2013 Bellone et al
Clustering and PCA for reconstructing two perpendicular planes using ultrasonic sensors: Regular paper
No full textIn this paper, the authors make use of sonar transducers to detect the corner of two orthogonal panels and they propose a strategy for accurately reconstructing the surfaces. In order to point a linear array of four sensors at the desired position, the motion of a digital motor is appropriately controlled. When the sensors are directed towards the intersection between the planes, longer times of flight are observed because of multiple reflections. All the concerned distances have to be excluded and that is why an indicator based on the output signal energy is introduced. A clustering technique allows for the partitioning of the dataset in three clusters and the indicator selects the subset containing misrepresented information. The remaining distances are corrected so as to take into consideration the directivity and they permit the plotting of two sets of points in a three-dimensional space. In order to leave out the outliers, each set is filtered by means of a confidence ellipsoid which is defined by the Principal Component Analysis (PCA). The best-fit planes are obtained based on the principal directions and the variances. Experimental tests and results are shown demonstrating the effectiveness of this new approach. © 2013 Licensee InTech
Large interatrial thrombus-in-transit resulting in acute myocardial infarction complicated by atrioventricular block and cardiogenic shock
No full text3D traversability awareness for rough terrain mobile robots
No full textThis research aims to address the issue of safe navigation for autonomous vehicles in highly challenging outdoor environments. Indeed, robust navigation of autonomous mobile robots over long distances requires advanced perception means for terrain traversability assessment. Design/methodology/ approach - The use of visual systems may represent an efficient solution. This paper discusses recent findings in terrain traversability analysis from RGB-D images. In this context, the concept of point as described only by its Cartesian coordinates is reinterpreted in terms of local description. As a result, a novel descriptor for inferring the traversability of a terrain through its 3D representation, referred to as the unevenness point descriptor (UPD), is conceived. This descriptor features robustness and simplicity. Findings - The UPD-based algorithm shows robust terrain perception capabilities in both indoor and outdoor environment. The algorithm is able to detect obstacles and terrain irregularities. The system performance is validated in field experiments in both indoor and outdoor environments. Research limitations/implications - The UPD enhances the interpretation of 3D scene to improve the ambient awareness of unmanned vehicles. The larger implications of this method reside in its applicability for path planning purposes. Originality/value - This paper describes a visual algorithm for traversability assessment based on normal vectors analysis. The algorithm is simple and efficient providing fast real-time implementation, since the UPD does not require any data processing or previously generated digital elevation map to classify the scene. Moreover, it defines a local descriptor, which can be of general value for segmentation purposes of 3D point clouds and allows the underlining geometric pattern associated with each single 3D point to be fully captured and difficult scenarios to be correctly handle
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