2,864 research outputs found
Robotic Tankette for Intelligent BioEnergy Agriculture: Design, Development and Field Tests
In recent years, the use of robots in agriculture has been increasing mainly
due to the high demand of productivity, precision and efficiency, which follow
the climate change effects and world population growth. Unlike conventional
agriculture, sugarcane farms are usually regions with dense vegetation,
gigantic areas, and subjected to extreme weather conditions, such as intense
heat, moisture and rain. TIBA - Tankette for Intelligent BioEnergy Agriculture
- is the first result of an R&D project which strives to develop an autonomous
mobile robotic system for carrying out a number of agricultural tasks in
sugarcane fields. The proposed concept consists of a semi-autonomous, low-cost,
dust and waterproof tankette-type vehicle, capable of infiltrating dense
vegetation in plantation tunnels and carry several sensing systems, in order to
perform mapping of hard-to-access areas and collecting samples. This paper
presents an overview of the robot mechanical design, the embedded electronics
and software architecture, and the construction of a first prototype.
Preliminary results obtained in field tests validate the proposed conceptual
design and bring about several challenges and potential applications for robot
autonomous navigation, as well as to build a new prototype with additional
functionality.Comment: 9 pages, 15 figure
Energy Dissipation and Trapping of Particles Moving on a Rough Surface
We report an experimental, numerical and theoretical study of the motion of a
ball on a rough inclined surface. The control parameters are , the diameter
of the ball, , the inclination angle of the rough surface and ,
the initial kinetic energy. When the angle of inclination is larger than some
critical value, , the ball moves at a constant average
velocity which is independent of the initial conditions. For an angle , the balls are trapped after moving a certain distance. The
dependence of the travelled distances on , and . is
analysed. The existence of two kinds of mechanisms of dissipation is thus
brought to light. We find that for high initial velocities the friction force
is constant. As the velocity decreases below a certain threshold the friction
becomes viscous.Comment: 8 pages RevTeX, 12 Postscript figure
Portuguese colonial architectural archives at the Arquivo HistĂłrico Ultramarino, mid 19th century - 1975
The Arquivo HistĂłrico Ultramarino (AHU - Overseas Historical Archive) holds Portuguese
architectural and also engineering archival records created and managed by the Colonial Public
Offices seated in Lisbon, dating back to the end of the 16th century to 1975. The archives from the
offices that performed duties in the Portuguese colonies remained there, even after their
independence from Portugal. Until recently, records dated from the mid 19th century onwards were
poorly identified, a panorama that changed over the last decade. These records are related to Angola,
Cabo Verde, Guinea-Bissao, SĂŁo TomĂ© and PrĂncipe, Mozambique, previous Portugese possessions
in India, Macao and East Timor. The AHU hosted two funded projects by the Portuguese
Foundation to Science and Technology (FCT) submitted by the Centre for Socioeconomic and
Territorial Studies from the Lisbon University Institute (DINĂMIA'CET-IUL). The participation of
the AHU in both projects allowed processing these records bulk. The first one was âThe Colonial
Urbanization Officesâ, a three year project which benefited from the collaboration of five archival
fellowships during nearly two years. The second project is the âCoast to Coastâ, has a similar duration
to the previous and will be ongoing until December 2019, with the contribution of an archival
fellowship. Two archivists of the AHU participated in these projects as well, supervising the archival
processing as researchers.info:eu-repo/semantics/publishedVersio
Effect of boundary conditions on diffusion in two-dimensional granular gases
We analyze the influence of boundary conditions on numerical simulations of
the diffusive properties of a two dimensional granular gas. We show in
particular that periodic boundary conditions introduce unphysical correlations
in time which cause the coefficient of diffusion to be strongly dependent on
the system size. On the other hand, in large enough systems with hard walls at
the boundaries, diffusion is found to be independent of the system size. We
compare the results obtained in this case with Langevin theory for an elastic
gas. Good agreement is found. We then calculate the relaxation time and the
influence of the mass for a particle of radius in a sea of particles of
radius . As granular gases are dissipative, we also study the influence of
an external random force on the diffusion process in a forced dissipative
system. In particular, we analyze differences in the mean square velocity and
displacement between the elastic and inelastic cases.Comment: 15 figures eps figures, include
On the velocity distributions of the one-dimensional inelastic gas
We consider the single-particle velocity distribution of a one-dimensional
fluid of inelastic particles. Both the freely evolving (cooling) system and the
non-equilibrium stationary state obtained in the presence of random forcing are
investigated, and special emphasis is paid to the small inelasticity limit. The
results are obtained from analytical arguments applied to the Boltzmann
equation along with three complementary numerical techniques (Molecular
Dynamics, Direct Monte Carlo Simulation Methods and iterative solutions of
integro-differential kinetic equations). For the freely cooling fluid, we
investigate in detail the scaling properties of the bimodal velocity
distribution emerging close to elasticity and calculate the scaling function
associated with the distribution function. In the heated steady state, we find
that, depending on the inelasticity, the distribution function may display two
different stretched exponential tails at large velocities. The inelasticity
dependence of the crossover velocity is determined and it is found that the
extremely high velocity tail may not be observable at ``experimentally
relevant'' inelasticities.Comment: Latex, 14 pages, 12 eps figure
Electrocatalytic oxidation of methanol by the [Ru3O(OAc)6(py)2(CH3OH)] 3+ cluster: improving the metal-ligand electron transfer by accessing the higher oxidation states of a multicentered system
The [Ru3O(Ac)6(py)2(CH3OH)] + cluster provides an effective electrocatalytic species for the oxidation of methanol under mild conditions. This complex exhibits characteristic electrochemical waves at -1.02, 0.15 and 1.18 V, associated with the Ru3III,II,II/Ru3III,III,II/Ru 3III,III,III /Ru3IV,III,III successive redox couples, respectively. Above 1.7 V, formation of two RuIV centers enhances the 2-electron oxidation of the methanol ligand yielding formaldehyde, in agreement with the theoretical evolution of the HOMO levels as a function of the oxidation states. This work illustrates an important strategy to improve the efficiency of the oxidation catalysis, by using a multicentered redox catalyst and accessing its multiple higher oxidation states331020462050CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTĂFICO E TECNOLĂGICO - CNPQCOORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIOR - CAPESFUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO - FAPESPSem informaçãoSem informaçãoSem informaçã
Reversible post-breakdown conduction in aluminum oxide-polymer capacitors
Aluminum/Al2O3/polymer/metal capacitors submitted to a low-power constant current stress undergo dielectric breakdown. The post-breakdown conduction is metastable, and over time the capacitors recover their original insulating properties. The decay of the conduction with time follows a power law (1/t)(alpha). The magnitude of the exponent alpha can be raised by application of an electric field and lowered to practically zero by optical excitation of the polyspirofluorene polymer. The metastable conduction is attributed to formation of metastable pairs of oppositely charged defects across the oxide-polymer interface, and the self-healing is related to resistive switching. (C) 2013 AIP Publishing LLC [http://dx.doi.org/10.1063/1.4802485
Mobile Device Forensics Framework: A Toolbox to Support and Enhance This Process
Cybercrime is growing rapidly, and it is increasingly important to use advanced tools to combat it and support investigations. One of the battlefronts is the forensic investigation of mobile devices to analyze their misuse and recover information. Mobile devices present numerous challenges, including a rapidly changing environment, increasing diversity, and integration with the cloud/IoT. Therefore, it is essential to have a secure and reliable toolbox that allows an investigator to thwart, discover, and solve all problems related to mobile forensics while deciphering investigations, whether criminal, civil, corporate, or other. In this work, we propose an original and innovative instantiation of a structure in a forensic toolbox for mobile devices, corresponding to a set of different applications, methods, and best practice information aimed at improving and perfecting the investigative process of a digital investigator. To ensure scientific support for the construction of the toolbox, the Design Science Research (DSR) methodology was applied, which seeks to create new and unique artifacts, drawing on the strength and knowledge of science and context. The toolbox will help the forensic investigator overcome some of the challenges related to mobile devices, namely the lack of guidance, documentation, knowledge, and the ability to keep up with the fast-paced environment that characterizes the mobile industry and market. Doi: 10.28991/ESJ-2024-08-03-011 Full Text: PD
Factors associated with quality of services for marginalized groups with mental health problems in 14 European countries
This research was financially supported by DG-Sanco (contract: 800197; 2007-2010). The authors would like to thank all of the professionals and services who participated in the PROMO assessment of services.
A PhD grant from Fundação para a CiĂȘncia e TecnologiaâPortugal (SFRH/BD/66388/2009) to the first author is acknowledged
- âŠ