376 research outputs found
Analysis of the Compliance Properties of an Industrial Robot with the Mozzi Axis Approach
In robotic processes, the compliance of the robot arm plays a very important role. In some conditions, for example, in robotic assembly, robot arm compliance can compensate for small position and orientation errors of the end-effector. In other processes, like machining, robot compliance may generate chatter vibrations with an impairment in the quality of the machined surface. In industrial robots, the compliance of the end-effector is chiefly due to joint compliances. In this paper, joint compliances of a serial six-joint industrial robot are identified with a novel modal method making use of specific modes of vibration dominated by the compliance of only one joint. Then, in order to represent the effect of the identified compliances on robot performance in an intuitive and geometric way, a novel kinematic method based on the concept of \u201cMozzi axis\u201d of the end-effector is presented and discusse
Quality maintenance performance and resistance to Tribolium castaneum and Plodia interpunctella penetration of an alternative packaging material for semolina
Insect attacks to food packages are a major concern for food producers, who are often blamed for being responsible for the occurrence of contamination which seriously affects the image of the company. Wheat semolina is commonly packed in paper bags, which do not always offer sufficient protection against insect pests. The present research evaluated the performance of a new packaging alternative, consisting of paper laminated with polypropylene (P+CPP), in terms of resistance to penetration by two common cereal product pests, namely Tribolium castaneum and Plodia interpunctella, and quality maintenance of the packaged product. Neither of the two pest species tested were able to pierce the P+CPP, while no differences were observed in the time required to penetrate other materials. Moreover, quality parameters, namely pH, acidity and color, did not differ significantly among samples packed in different materials. The new P+CPP combination is a promising alternative for the packaging of semolina, because it offers improved protection against pests compared with conventional materials, while maintaining the paper appearance of traditional packaging
The Role of the Internal Capacitance in Organic Memristive Device for Neuromorphic and Sensing Applications
Organic electronics has recently emerged as a promising candidate for the emulation of brain-like functionalities, especially at the device level. Among the proposed technologies, memristive devices have gained an increasing attention due to their non-volatile behavior which makes them suitable for the implementation of artificial neuronal networks. However, most of them have an energy-costly switching mechanism which limits the approach of brain like energy efficiency. Different from them, organic memristive devices (OMDs) have a narrow switching window and implement neuromorphic characteristics at voltages <= 1 V. Despite OMDs potentialities in bioinspired electronics, guidelines for the design of devices and materials are still missing. Here it is shown that the device capacitance represents a significant degree of freedom for targeting devices applications. It is also shown that a single OMD emulates activity dependent synaptic functions and neuronal temporal and spatial summation, taking advantage of its three-terminals configuration. Interestingly, despite the neuromorphic applications, OMDs can also sense and amplify incoming signals on the basis of their capacitive and/or resistive values. This spectrum of applications, ranging from volatile to non-volatile characteristics and from neuromorphic computing to bio signals sensing, sets the stage for the realization of integrated circuits for adaptive sensing
Transversity distributions and tensor charges of the nucleon: extraction from dihadron production and their universal nature
We perform the first global quantum chromodynamics (QCD) analysis of dihadron
production for a comprehensive set of data in electron-positron annihilation,
semi-inclusive deep-inelastic scattering, and proton-proton collisions, from
which we extract simultaneously the transversity distributions of the nucleon
and dihadron fragmentation functions. We incorporate in our fits
known theoretical constraints on transversity, namely, its small- asymptotic
behavior and the Soffer bound. We furthermore show that lattice-QCD results for
the tensor charges can be successfully included in the analysis. This resolves
the previously reported incompatibility between the tensor charges extracted
from dihadron production data and lattice QCD. We also find agreement with
results for the transversity and tensor charges obtained from measurements on
single-hadron production. Overall, our work demonstrates for the first time the
universal nature of all available information for the transversity
distributions and the tensor charges of the nucleon
On the Interpretation of Hysteresis Loop for Electronic and Ionic Currents in Organic Memristive Devices
Being promising elements for neuromorphic computation, memristive devices have been often described as crucial elements for mimicking important synapse properties, such as memory and learning. Among them, organic memristive devices (OMDs) can claim low-cost fabrication processes and the easy tunability of their electrical properties. Up to now, the major bottleneck for their larger uses in neuromorphic computation is low rate of the resistance switching and stability. Herein, a new approach is reported, based on the use of a liquid electrolyte, leading to the manufacturing of OMD with higher stability and faster resistive switching
First Simultaneous Global QCD Analysis of Dihadron Fragmentation Functions and Transversity Parton Distribution Functions
We perform a comprehensive study within quantum chromodynamics (QCD) of
dihadron observables in electron-positron annihilation, semi-inclusive
deep-inelastic scattering, and proton-proton collisions, including recent cross
section data from Belle and azimuthal asymmetries from STAR. We extract
simultaneously for the first time dihadron fragmentation functions
(DiFFs) and the nucleon transversity distributions for up and down quarks as
well as antiquarks. For the transversity distributions we impose their
small- asymptotic behavior and the Soffer bound. In addition, we utilize a
new definition of DiFFs that has a number density interpretation to then
calculate expectation values for the dihadron invariant mass and momentum
fraction. Furthermore, we investigate the compatibility of our transversity
results with those from single-hadron fragmentation (from a transverse momentum
dependent/collinear twist-3 framework) and the nucleon tensor charges computed
in lattice QCD. We find a universal nature to all of this available
information. Future measurements of dihadron production can significantly
further this research, especially, as we show, those that are sensitive to the
region of large parton momentum fractions.Comment: 34 pages, 24 figure
Null-Space Minimization of Center of Gravity Displacementof a Redundant Aerial Manipulator
Displacements of the base during trajectory tracking are a common issue in the control of aerial manipulators. These are caused by reaction torques transferred to the base due to the manipulator motion and, in particular, to the motion of its center of gravity. We present a novel approach to reduce base displacements of a kinematically redundant aerial manipulator by using null-space projection in the inverse kinematic control. A secondary objective function minimizes the horizontal displacement of the manipulator center of gravity. We test this algorithm on different trajectories for both three and four degrees of freedom (DOF) manipulators in a simulation environment. The results comparing our algorithm with inverse kinematic control without the null-space projection show up to an 80% reduction in the end-effector position error and an average of about 56% reduction in maximum base displacement. The simulation implementation also runs faster than in real-time in our code implementation. We provide a workspace analysis based on multiple stopping criteria such as excessive base displacement, joint velocities and end-effector position error for the 3 and 4 DOF manipulators. As expected, the 4 DOF manipulator has a larger workspace
Long-term subjective outcomes of barbed reposition pharyngoplasty for obstructive sleep apnea syndrome treatment
Background: The purpose of this study was to evaluate long-term subjective outcomes of barbed reposition pharyngoplasty for obstructive sleep apnea syndrome (OSAS) treatment using a specific questionnaire, the Palate Postoperative Problem Score (PPOPS). Methods: 140 patients who underwent barbed reposition pharyngoplasty (BRP) surgery in the Morgagni Pierantoni Hospital of Forlì, Italy were enrolled in the study. Postoperative outcomes were evaluated in a short- and long-term follow-up using the PPOPS questionnaire. The average period of follow-up was 26 months. All patients received the PPOPS questionnaire by telephone in a period between April and August 2019. Results: 51% of patients complained of swallowing problems after surgery. In 91% of cases, the problem cleared up spontaneously. At the time of the interview, only 9% of patients had a residual swallowing difficult. At the time of PPOPS evaluation, rhinolalia was observed in 8% of patients, whereas nose regurgitation was present in 2% of patients. In 20% of patients, the foreign body sensation was present during follow-up. The value of apnea-hypopnea index (AHI) reduced from the preoperative value of 31.5 to the postoperative value of 11.4. Conclusions: BRP surgery proved to be an effective technique, appreciated by the majority of patients. Use of the PPOPS questionnaire has demonstrated that the BRP technique seems to ensure efficacy and lower morbidity, with few complications after surgery
Psoas abscess ten years after ipsilateral nephrectomy for pyonephrosis
Pyogenic abscess of the psoas muscle is a rare disease. The Authors
report a recently observed case which developed 10 years after ipsilateral nephrectomy for pyonephrosis, reviewing the pertinent literature.
The culture of the pus extracted only reproduced Proteus mirabilis. The
relation between psoas abscess and nephrectomy is unclear. To make
diagnosis is important to consider this condition in differential diagnosis in presence of fever and flank tenderness in a nephrectomized patient
Isovector EMC effect from global QCD analysis with MARATHON data
We report the results of a Monte Carlo global QCD analysis of unpolarized
parton distribution functions (PDFs), including for the first time constraints
from ratios of He to H structure functions recently obtained by the
MARATHON experiment at Jefferson Lab. Our simultaneous analysis of nucleon PDFs
and nuclear effects in and nuclei reveals the first indication for
an isovector nuclear EMC effect in light nuclei. We find that while the
MARATHON data yield relatively weak constraints on the neutron to
proton structure function ratio and on the PDF ratio, they suggest an
enhanced nuclear effect on the -quark PDF in the bound proton, questioning
the assumptions commonly made in nuclear PDF analyses.Comment: 6 pages, 3 figure
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