1,721,090 research outputs found
Robot Motion Evaluation by means of a Stereoscopic Vision System
No full textThis paper presents an algorithm for using the stereoscopic vision in environmental recognition and in particular in the motion detection. The algorithm is based on the recognition of certain environmental characteristics, in particular straight-line segments, to be identified in two distinct stereoscopic observations of the working environment. The study of such an algorithm aims to promote the integration of stereoscopic vision in robotic applications, especially in mobile robots. Some results are presented with reference to a stereoscopic vision system applied to a 3 d.o.f. revolute robot
An algorithm for robot motion detection by means of a stereoscopic vision system
No full textThis paper presents an algorithm for using the stereoscopic vision in environmental recognition and in particular in the motion detection. The algorithm is based on the recognition of certain environmental characteristics, in particular straight-line segments, to be identified in two distinct stereoscopic observations of the working environment. The knowledge of some environmental characteristics of a scene observed from different positions allows estimating the transformation between the observation positions. The study of such algorithm aims to promote the integration of stereoscopic vision in robotics, especially in mobile and autonomous robots, and to promote the use of these methodologies to improve the possibilities of control in the robotic applications. Some results are presented with reference to a stereoscopic vision system applied to a 3 d.o.f. revolute robot. © 2013 Taylor & Francis and The Robotics Society of Japan
ROBOT PER LA SCANSIONE E LA REPLICA DI SUPERFICI
No full textQuesta invenzione fa riferimento al campo della tecnica relativo alle macchine utensili comandate da robot in grado di riprodurre superfici a partire da un modello CAD. Lo stato dell’arte circa la riproduzione di superfici utilizzando utensili mediante l’ausilio di un robot prevede svariati modelli di macchine, che si differenziano a seconda delle forme da riprodurre e dalle dimensioni. Tutte però si basano su una logica che prevede un caricamento della matematica del modello CAD da realizzare sul software che comanda il robot, per poi avviarne la riproduzione reale utilizzando differenti utensili. L’invenzione proposta da questo brevetto, riguarda un robot dotato di un sistema di scansione laser incorporato per la scansione e la replica di superfici. Il vantaggio di un sistema di questo tipo risiede nel fatto di non dover più effettuare una scansione della superficie da replicare mediante un'altra macchina che necessita una successiva rielaborazione dei dati ad esempio mediante logica best fitting ma l’obiettivo è quello di sfruttare gli stessi dati acquisiti dal robot in maniera diretta per la digitalizzazione e successiva replica della superficie da riprodurre
Robot Trajectory Planning by Points and Tangent Lines
No full textAt the Di.M.E. of the University of Naples - “Federico II” a technique for robot trajectories planning was studied; by means of the latter, a better precision of the trajectory itself was achieved.
With the proposed technique, not only the points that the end-effector must go across are assigned but also the tangent lines to the path in each of those given points. The latter condition is achieved by assigning the velocity of each of the joints in the joint space.
In order to carry on the proposed technique, it was performed the possibility to operate a robot by assigning to the control system not only the joint variables {qi} but also the vector {qi}. of the velocities that each of the joint must perform in correspondence of each of the points assigned to define the end-effector path.
In the paper are reported some comparisons between the trajectories obtained by traditional techniques and those obtained by the proposed technique. The comparisons clearly show that, generally, by the proposed technique paths closed to the planned ones are obtained, also assigning a much lower number of points
Liquid-Cooled Microchannel Heat Sink Thermal Analysis Using a Porous-Medium Model
No full textThe use of liquid-cooled microchannel heat sinks (MCHSs), both in single-layered and double-layered configurations, represents a well-established practice for the thermal control of electronic chips in integrated circuits[1]. For the optimization of these devices, CFD plays a crucial role, but in the past most numerical simulations were carried out under the scenario of heat sinks with all parallel microchannel (with co-current or counter flow configurations for double-layered MCHSs). In these cases, in fact, by taking advantage of geometrical symmetries, it is possible to refer to extremely basic computational domains made up of one half-channel or two stacked half-channels [2]. As a result, more intricate heat sink designs have hardly ever been investigated due to the prohibitive computing cost required for their domain discretization, which calls for a very high number of cells. This means that not only was the crossflow configuration seldom considered, but effects of flow maldistribution and parasitic heat transfer in headers were also disregarded. To allow an approximate thermal analysis of entire micro microchannel heat sinks, possibly including the manifolds, an alternative method is presented, which involves treating an entire layer of microchannels as a porous medium with properties empirically determined based on comparisons of results of 3D simulations for a single microchannel of the heat sink and those of calibration tests of a 2D porous-medium model. The porous-medium approach has previously been shown to be valid, particularly when used in conjunction with the local thermal non-equilibrium (LTNE) method. Commercial software with the LTNE option can be used for this kind of analysis. Nevertheless, even though Ansys Fluent [3], one of the most widely used of these codes, features the LTNE model, it is unable to account for heat transfer between the solid porous matrix and the nearby solid portions of the domain. To get around the issue and enable the use of the porous-medium technique in conjunction with the LTNE model of Ansys Fluent, a novel approach is proposed in this study. Since in Ansys Fluent the porous solid zone only interacts with the fluid and not with the solid walls with regard to heat transfer, a thin fluid layer is defined, where the velocity is zero, the thermal conductivity of the fluid is equal to that of the solid, and the fluid-solid interfacial heat transfer coefficient is very large so that the adiabatic boundary of the porous solid matrix can be short-circuited. The method is validated by the successful comparison of computed results with those from accurate analyses concerning double-layered microchannel heat sinks with non-uniform velocity distributions, that are carried out using an in-house FEM procedure [4]. It is thus proved that the suggested approach can be applied with confidence for the study of the thermal performance of micro heat sinks with complex geometries while saving a significant amount of computational work
A Smart Gluing Process by a Vision Guided Robotic System
No full textThe paper describes the improvement of an automatic machine that dispenses glue on objects placed on a worktop; in particular, the machine was developed to glue the upper and the rubber inserts on the soles of the shoes. The system is characterized by the presence of a vision system which has the purpose of locating the position of the soles lying on the worktop and of reconstructing their geometries. This information is used to plan the trajectory of a Cartesian robot that drives the glue gun with an error that can be considered acceptable for this operation. The paper reports the procedures used to perform these operations which differ depending on whether the sole can be treated as a flat object, characterized by negligible height variations or if it has a three-dimensional geometry with significant variations in height. In the latter case, the gluing path performed by the robot must consider the height variation to keep the glue gun at the same distance from the sole along the entire gluing path. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG
Paraoxonase activity in high density lipoproteins: a comparison between healthy and obese females
No full textJ Clin Endocrinol Metab. 2005 Mar;90(3):1728-33. Epub 2004 Dec 21.
Paraoxonase activity in high-density lipoproteins: a comparison between healthy and obese females.
Ferretti G, Bacchetti T, Moroni C, Savino S, Liuzzi A, Balzola F, Bicchiega V.
SourceIstituto di Biochimica, Facoltà di Medicina e Chirurgia, Università Politecnica delle Marche, Via Ranieri, 60131 Ancona, Italy. [email protected]
Abstract
Paraoxonase, an enzyme associated with high-density lipoprotein (HDL-PON), exerts a protective effect against oxidative damage of circulating cells and lipoproteins, modulates the susceptibility of HDL to atherogenic modifications such as glycation and homocysteinylation, and even exerts an antiinflammatory role. The aim of the present study was to investigate the relationship between lipoprotein oxidative stress and the activity of HDL-PON in healthy and obese subjects. Therefore, the activity of HDL-PON and the levels of lipid hydroperoxides in HDL and low-density lipoprotein (LDL) isolated from plasma of obese females (n = 12) and age-sex-matched controls (n = 31) were compared. Our results demonstrated for the first time that the activity of HDL-PON in obese subjects was significantly lower compared with that in controls (P < 0.001). Moreover, our results showed a significant increase in the levels of lipid hydroperoxides in HDL and LDL isolated from obese subjects (P < 0.001). The negative correlations established between HDL-PON activity and the levels of lipid hydroperoxides associated with HDL and LDL confirm the relationship between paraoxonase activity and lipid peroxidation of lipoproteins. Plasma levels of leptin correlated negatively with HDL-PON activity and positively with levels of lipid hydroperoxides in HDL and LDL of obese subjects, suggesting a relationship between leptin and oxidative damage of lipoproteins. In conclusion, our study demonstrated that the increase in oxidative stress in LDL and HDL of obese subjects is associated with a decrease in HDL-PON activity. The lower paraoxonase activity and the compositional changes in HDL and LDL could contribute to the greater risk of cardiovascular disease associated with obesity.
PMID:15613429[PubMed - indexed for MEDLINE
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
Entrainment temporal evolution across stably and unstably stratified vapor/clear air interfaces
No full textWarm clouds as stratocumuli swathe a significant part of earth’s surface and play a major role in the global dynamics of atmosphere by strongly reflecting incoming solar radiation so that an accurate representation of their dynamics is important in large-scale analyses of atmoshperic flows [Wood 2012].The mixing and entrainment processes at the cloud top have been identified as fundamental to determine the internal structure of warm clouds, so that a clear and complete understanding of their physics is required [Gerber et al 2013]. The aim of this work is to study some of the basic phenomena which occur at a stratified interface focusing on the smallest scales of the flow which influence. These scales are important to understand the global dynamic of clouds, as pointed out by Malinowski et al (2013). To achieve the results, a campaign of high-resolution simulation of the local transport through a dry/moist air were performed by the means of Direct Numerical Simulations (DNS) using our home produced computational code that implements a de-aliased pseudospectral Fourier-Galerkin spatial discretization and an explicit low storage fourth order Runge-Kutta time integration scheme [Iovieno et al 2001]. We consider the interface between clear air and moist air in a 6m × 6m × 12m parallelepipedic domain coupling two homogeneous and isotropic turbulent regions with different kinetic energy that interact through a mixing layer. The energy ratio is of the same order of the ones measured in warm clouds (see, e.g., [Malinowski et al 2013]) and, furthermore, it allows us to compare our results with experiments on shearless mixing (see [Veeravalli & Warhaft 1989, Tordella & Iovieno 2011]) in absence of any stratification. For each simulation two interfaces have been obtained, one in highly stably stratified condition, and one in unstable condition. The dynamics of interfaces is analyzed through an initial temperature perturbation located across one of the vapor/clear air interfaces thus generating a local stable layer; the water vapor is treated as a passive scalar. The level of stratification is quantified with the Froude number. For the stable cases, the Froude numbers considered ranges from 12.7 (weak stratification) to 0.6 (intense stratification), while for the unstable cases Fr^2 ranges from -250 to -16. In both stable and unstable cases the evolution of the system can be split in two different phases. In the first one, the buoyancy terms are negligible, and there are no significant differences with respect to a non-stratified case. As the system evolves, the effect of stratification becomes relevant (as soon as the stratification is intense). About the unstable case layer we observe a high intermittency and an intense growth rate of the layer, which becomes overdiffusive in the case Fr^2 = −16. In particular, the entrainment, after an initial decay, asimptotically always shows a positive growth rate. Here, for reason of space, we give details about the stably stratified layer which presents a more complex dynamics associated to the onset of a pocket very low turbulent kinetic energy. It can be observed the onset of a sub-layer characterized by the presence of low values of kinetic turbulent energy. At about 8 time scales, we observe the 8% of the energy in the wapor cloud and the 50% of the kinetic energy in the clear-air region. A similar trend was also observed in the LES cloud topped boundary layer simulations carried out by using Deardoff TKE model (NCAR group) and by using the ARAP TKE model (WVU group) [Moeng et al 1996]. The presence of such sublayer induces the formation of two local interfaces. Both of these interfaces present an intermittent behavior, and the entrainment (flux of dry air into the moist one) is blocked; the velocity of the moist air front can be considered a characteristic parameter, since the entrainment of clear air is responsible of the growth of the cloud [Mellado 2010, Moeng 2000]. As a consequence, the entrainment of clear air is confined to a thin interfacial layer. Also the dissipative terms inside the pit becomes relatively more important compared to the kinetic energy, making the pit deeper and deeper with respect to the external regions
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