628 research outputs found
A Review of Current and Historical Research Contributions to the Development of Ground Autonomous Vehicles for Agriculture
In this study, a comprehensive overview of the available autonomous ground platforms developed by universities and research groups that were specifically designed to handle agricultural tasks was performed. As cost reduction and safety improvements are two of the most critical aspects for farmers, the development of autonomous vehicles can be of major interest, especially for those applications that are lacking in terms of mechanization improvements. This review aimed to provide a literature evaluation of present and historical research contributions toward designing and prototyping agricultural ground unmanned vehicles. The review was motivated by the intent to disseminate to the scientific community the main features of the autonomous tractor named BOPS-1960, which was conceived in the 1960s at the Alma Mater Studiorum University of Bologna (UNIBO). Jointly, the main characteristics of the modern DEDALO unmanned ground vehicle (UGV) for orchard and vineyard operations that was designed recently were evaluated. The basic principles, technology and sensors used in the two UNIBO prototypes are described in detail, together with an analysis of UGVs for agriculture conceived in recent years by research centers all around the world
Strict inequalities of critical values in continuum percolation
We consider the supercritical finite-range random connection model where the
points of a homogeneous planar Poisson process are connected with
probability for a given . Performing percolation on the resulting
graph, we show that the critical probabilities for site and bond percolation
satisfy the strict inequality . We also show
that reducing the connection function strictly increases the critical
Poisson intensity. Finally, we deduce that performing a spreading
transformation on (thereby allowing connections over greater distances but
with lower probabilities, leaving average degrees unchanged) {\em strictly}
reduces the critical Poisson intensity. This is of practical relevance,
indicating that in many real networks it is in principle possible to exploit
the presence of spread-out, long range connections, to achieve connectivity at
a strictly lower density value.Comment: 38 pages, 8 figure
Energy absorption in actual tractor rollovers with different tire configurations
In order to better understand the complexities of modern tractor rollover, this paper investigates the energy absorbed by a Roll-Over Protective Structure (ROPS) cab during controlled lateral rollover testing carried out on a modern narrow-track tractor with a silent-block suspended ROPS cab. To investigate how different tractor set-ups may influence ROPS and energy partitioning, tests were conducted with two different wheel configurations, wide (equivalent to normal ‘open field’ operation) and narrow (equivalent to ‘orchard/vineyard’ operation), and refer to both the width of the tires and the corresponding track. Dynamic load cells and displacement transducers located at the ROPS-ground impact points provided a direct measurement of the energy absorbed by the ROPS cab frame. A trilateration method was developed and mounted onboard to measure load cell trajectory with respect to the cab floor in real-time. The associated video record of each rollover event provided further information and opportunity to explain the acquired data. The narrow tire configuration consistently subjected the ROPS cab frame to more energy than the wide tire arrangement. To better evaluate the influence of the ROPS cab silent-blocks in lateral rollover, static and dynamic tests were performed. The results confirm that tires influence the energy partition significantly and that further understanding of silent-blocks’ dynamic performance is warranted
Impact of boundaries on fully connected random geometric networks
Many complex networks exhibit a percolation transition involving a
macroscopic connected component, with universal features largely independent of
the microscopic model and the macroscopic domain geometry. In contrast, we show
that the transition to full connectivity is strongly influenced by details of
the boundary, but observe an alternative form of universality. Our approach
correctly distinguishes connectivity properties of networks in domains with
equal bulk contributions. It also facilitates system design to promote or avoid
full connectivity for diverse geometries in arbitrary dimension.Comment: 6 pages, 3 figure
Temperature Dependent Empirical Pseudopotential Theory For Self-Assembled Quantum Dots
We develop a temperature dependent empirical pseudopotential theory to study
the electronic and optical properties of self-assembled quantum dots (QDs) at
finite temperature. The theory takes the effects of both lattice expansion and
lattice vibration into account. We apply the theory to the InAs/GaAs QDs. For
the unstrained InAs/GaAs heterostructure, the conduction band offset increases
whereas the valence band offset decreases with increasing of the temperature,
and there is a type-I to type-II transition at approximately 135 K. Yet, for
InAs/GaAs QDs, the holes are still localized in the QDs even at room
temperature, because the large lattice mismatch between InAs and GaAs greatly
enhances the valence band offset. The single particle energy levels in the QDs
show strong temperature dependence due to the change of confinement potentials.
Because of the changes of the band offsets, the electron wave functions
confined in QDs increase by about 1 - 5%, whereas the hole wave functions
decrease by about 30 - 40% when the temperature increases from 0 to 300 K. The
calculated recombination energies of exciton, biexciton and charged excitons
show red shifts with increasing of the temperature, which are in excellent
agreement with available experimental data
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Simple method for sub-diffraction resolution imaging of cellular structures on standard confocal microscopes by three-photon absorption of quantum dots
This study describes a simple technique that improves a recently developed 3D sub-diffraction imaging method based on three-photon absorption of commercially available quantum dots. The method combines imaging of biological samples via tri-exciton generation in quantum dots with deconvolution and spectral multiplexing, resulting in a novel approach for multi-color imaging of even thick biological samples at a 1.4 to 1.9-fold better spatial resolution. This approach is realized on a conventional confocal microscope equipped with standard continuous-wave lasers. We demonstrate the potential of multi-color tri-exciton imaging of quantum dots combined with deconvolution on viral vesicles in lentivirally transduced cells as well as intermediate filaments in three-dimensional clusters of mouse-derived neural stem cells (neurospheres) and dense microtubuli arrays in myotubes formed by stacks of differentiated C2C12 myoblasts
Acute effects of whole-body vibrations on the fatigue induced by multiple repeated sprint ability test in soccer players
Background: We tested the hypothesis that whole-body vibration (WBV) positively affects the fatigue process ensuing from repeated bouts of maximal efforts, as induced by repeated sprints' ability (RSA). Eleven male soccer players performed three sets of six repeated shuttle sprints (40 meters).
Methods: Eleven male soccer players (age 23.6±4.5 years) were cross-randomized to perform WBW before RSA and during the recovery between sets (WBV-with) or to warm-up and passive recovery between sets (WBV-without). The effects of WBV were quantified by sprint time (ST) and blood lactate concentration (LA), collected up to 15 min after completion of tests.
Results: ST during RSA showed a better maintenance of performance in the WBV-with compared to WBV-without condition in all three sets, reaching a statistical significance between-groups during the 2nd and 3rd set (P<0.05). No significant differences in ST over the sets were detected in WBV-with, whereas a significant decrease was observed in the WBV-without condition (P<0.001). LA recovered significantly faster from the 9th to 15th minute of recovery in WBV-with as compared to WBV-without (P<0.05).
Conclusions: These findings would indicate that WBV performed during recovery between RSA sets can delay the onset of muscle fatigue resulting in a better maintenance of sprint performance
DNA damage and transcriptional regulation in iPSC-derived neurons from Ataxia Telangiectasia patients
Abstract Ataxia Telangiectasia (A-T) is neurodegenerative syndrome caused by inherited mutations inactivating the ATM kinase, a master regulator of the DNA damage response (DDR). What makes neurons vulnerable to ATM loss remains unclear. In this study we assessed on human iPSC-derived neurons whether the abnormal accumulation of DNA-Topoisomerase 1 adducts (Top1ccs) found in A-T impairs transcription elongation, thus favoring neurodegeneration. Furthermore, whether neuronal activity-induced immediate early genes (IEGs), a process involving the formation of DNA breaks, is affected by ATM deficiency. We found that Top1cc trapping by CPT induces an ATM-dependent DDR as well as an ATM-independent induction of IEGs and repression especially of long genes. As revealed by nascent RNA sequencing, transcriptional elongation and recovery were found to proceed with the same rate, irrespective of gene length and ATM status. Neuronal activity induced by glutamate receptors stimulation, or membrane depolarization with KCl, triggered a DDR and expression of IEGs, the latter independent of ATM. In unperturbed A-T neurons a set of genes (FN1, DCN, RASGRF1, FZD1, EOMES, SHH, NR2E1) implicated in the development, maintenance and physiology of central nervous system was specifically downregulated, underscoring their potential involvement in the neurodegenerative process in A-T patients
Theoretical interpretation of the experimental electronic structure of lens shaped, self-assembled InAs/GaAs quantum dots
We adopt an atomistic pseudopotential description of the electronic structure
of self-assembled, lens shaped InAs quantum dots within the ``linear
combination of bulk bands'' method. We present a detailed comparison with
experiment, including quantites such as the single particle electron and hole
energy level spacings, the excitonic band gap, the electron-electron, hole-hole
and electron hole Coulomb energies and the optical polarization anisotropy. We
find a generally good agreement, which is improved even further for a dot
composition where some Ga has diffused into the dots.Comment: 16 pages, 5 figures. Submitted to Physical Review
Entangled Photons from Small Quantum Dots
We discuss level schemes of small quantum-dot turnstiles and their
applicability in the production of entanglement in two-photon emission. Due to
the large energy splitting of the single-electron levels, only one single
electron level and one single hole level can be made resonant with the levels
in the conduction band and valence band. This results in a model with nine
distinct levels, which are split by the Coulomb interactions. We show that the
optical selection rules are different for flat and tall cylindrically symmetric
dots, and how this affects the quality of the entanglement generated in the
decay of the biexciton state. The effect of charge carrier tunneling and of a
resonant cavity is included in the model.Comment: 10 pages, 8 figure
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