440 research outputs found
Some Weighted Isoperimetric Problems on with Stable Half Balls Have No Solutions
No full textWe show the counter-intuitive fact that some weighted isoperimetric problems on the half-space , for which half-balls centered at the origin are stable, have no solutions.
A particular case is the measure , with . Some results on stability and nonexistence for weighted isoperimetric problems on are also obtained
Analytical models to assess the potential of waste-based industrial plants in the energy transition: an application to the steelmaking sector
No full textHuman activities, such as fossil fuel combustion and deforestation, have led to increased
greenhouse gas emissions and global warming. To mitigate these effects, countries have
pledged to limit global warming to 1.5°C and achieve carbon neutrality by 2050. This
requires a transition to renewable energy sources, including photovoltaic panels, wind
turbines, hydrogen, and biomethane. While progress has been made in the context of the
energy transition, additional actions are required to reach the goal of reducing greenhouse
gas emissions to net-zero.
The steelmaking sector is particularly challenging to decarbonise due to its reliance on
fossil fuels. However, the so-called secondary route, which involves melting recycled steel
scrap in an electric arc furnace, offers a real decarbonisation potential. This route can be
supported by the production of direct reduced iron, which can be produced using
hydrogen instead of natural gas.
Waste valorisation, which involves converting waste into energy or other valuable
products, can also play a role in the energy transition. Waste valorisation plants can indeed
produce both electricity, hydrogen, and biomethane. However, current waste valorisation
assessment methods lack consideration of their role in the ongoing energy transition.
Consistent with these gaps, the present work aims to develop analytical models to evaluate
waste valorisation plants' economic and environmental performance within the context of
the energy transition.
A cost and investment analysis carried out with respect to three waste-to-energy plants
allowed to identify gasification as the best option to support the current energy transition,
due to its high electricity output despite high operational costs. The application of the
environmental analytical models developed to compare different waste valorisation
alternatives from the anaerobic digestion of waste, showed that biomethane production is
better than electricity production, while hydrogen production is better than biomethane
production. Moreover, the application of an environmental analytical model to the EU
2020 and 2030 scenarios showed that waste-based hydrogen production routes offer
significant decarbonization potential.
An economic model moreover showed that the secondary steelmaking route, supported
by direct reduced iron production, prove to be profitable despite cost and carbon pricing fluctuations. An environmental analytical model allowed to find that national energy mixes
play a crucial role in enabling sector decarbonization. Finally, it was found that waste-based
hydrogen routes can accelerate decarbonization in steelmaking, enabling low-emission
steel production even before large-scale electrolyzer installation becomes viable.
These findings underscore the importance of incorporating energy transition
considerations into waste valorisation assessments to optimize resource utilization and
advance sustainable energy solutions
Symmetrization for singular semilinear elliptic equations
No full textIn this paper, we prove some comparison results for the solution to a Dirichlet problem associated with a singular elliptic equation and we study how the summability of such a solution varies depending on the summability of the datum f. © 2012 Fondazione Annali di Matematica Pura ed Applicata and Springer-Verlag
A class of degenerate elliptic equations and a Dido's problem with respect to a measure
No full textIn the present paper we study a class of linear elliptic equations in dimension N, whose coefficients have a type of singularity which appears, for instance, when one looks for axially symmetric solutions to elliptic equations in dimension greater then N, or, more in general, solutions which are symmetric with respect to a group of variables. We are interested in sharp apriori bounds for the solution to such a type of equations. Such type of problems can be studied by classical symmetrization methods. However the degeneracy of the operator does not allow to use the classical approach via Schwarz symmetrization . This leads us to consider an appropriate weighted symmetrization based on the structure of the problem and an suitable relative isoperimetric inequality
Systematic procedure for the identification of dynamic parameters of robot manipulators
No full textIn this paper a complete and systematic procedure for the identification of the dynamic parameters of rigid robot manipulators is presented. Starting from the basic results on the subject present in the literature and on a new technique to find exciting trajectories for the estimation, the procedure is developed. A set of algorithms is provided for the implementation of the various steps of the procedure for a generic open-chain structure. The algorithms have been coded in the popular Matlab/Maple environment and the procedure has been tested in a practical case study to identify the dynamic parameters of a six-degree-of-freedom conventional industrial robot
An experimental set-up for cooperative manipulation based on industrial manipulators
No full textDescribes the experience of setting up a cooperative arm system based on individual open-architecture controllers. Two six-degree-of-freedom industrial manipulators, one of which is mounted on a moving track, are installed to realize a cooperative experimental set-up. The main issues related to the cooperative manipulation are overviewed and its potential applications in industry are discussed. A brief description of the system’s components is given. The most relevant problems encountered in setting up the cooperative system based on individual control architectures are detailed. The result of the experience is that by using available industrial manipulators, rather than prototypes, and without re-designing the controller hardware, it is possible to realize a cooperative manipulator system
Evaluation of velocity capabilities for redundant parallel robots
No full textPolytopes are well-known tools to graphically represent force/motion capabilities for a manipulator. This paper focuses on the evaluation of velocity polytopes for redundant fully parallel robots for which a new intermediate space is introduced (in addition to classical joint space and task space) in order to take into account the specific kinematic relationships. In this space, additional constrainst are imposed on the available velocities to be consistent with the kinematic constraints due to the redundant kinematic chains. An algorithm to correctly evaluate the task space velocity polytope is given, and numerical results are provided in the case of a planar redundant 3-dof parallel arm
Experiments of feedforward control on a conventional industrial manipulator
No full textIn this paper, feedforward model-based control is experimented on a conventional industrial manipulator, the SMART-3 6.12R by COMAU. Despite of the fact that the conditions for the experiments are far from those provided by research set-ups, the obtained results confirm that it is worth using feedforward compensation control even on an industrial set-up
Identification of dynamic parameters and feedforward control for a conventional industrial manipulator
No full textDynamic compensation control algorithms can improve the performance of conventional industrial manipulators if an accurate dynamic model is available. Usually, the structure of the dynamic model is known but the actual values of the dynamic parameters are either unknown or not accurately known. It is thus required to perform an identification of these parameter using available algorithms. In this paper, feedforward model-based control is experimented on a conventional industrial robot, the SMART-3 6.12R by COMAU, based on a dynamic parameter identification. Despite the fact that the conditions for the experiments are far from those provided by research set-ups, the obtained results have confirmed that it is worth using feedforward compensation control, either in a complete or in a partial form, even on an industrial set-up
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