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51.
In this paper, we develop a theory of regular ω-languages that consist of ultimately periodic words only and we provide it
with an automaton-based characterization. The resulting class of automata, called ultimately periodic automata (UPA), is a
subclass of the class of Büchi automata and inherits some properties of automata over finite words (NFA). Taking advantage
of the similarities among UPA, Büchi automata, and NFA, we devise efficient solutions to a number of basic problems for UPA,
such as the inclusion, the equivalence, and the size optimization problems. The original motivation for developing a theory
of ultimately periodic languages and automata was to represent and to reason about sets of time granularities in knowledge-based
and database systems. In the last part of the paper, we show that UPA actually allow one to represent (possibly infinite)
sets of granularities, instead of single ones, in a compact and suitable to algorithmic manipulation way. In particular, we
describe an application of UPA to a concrete time granularity scenario taken from clinical medicine. 相似文献
52.
Gianluca Buffa Davide Campanella Livan Fratini Fabrizio Micari 《International Journal of Material Forming》2016,9(5):613-618
Friction Stir Extrusion is a novel technique for direct recycling of metal scrap. In the process, a dedicated tool produces both the heat and the pressure to compact and extrude the original raw material, i.e., machining chip, as a consolidated component. A proper fixture was used to carry out an experimental campaign on Friction Stir Extrusion of AZ31 magnesium alloy. Variable tool rotation and extrusion ratio were considered. Appearance of defects and fractures was related to either too high or too low power input. The extruded rods were investigated both from the metallurgical and mechanical points of view. Tensile strength up to 80 % of the parent material was found for the best combination of process parameters. A peculiar 3D helical material flow was highlighted through metallurgical observation of the specimens. 相似文献
53.
Qamer Zia Davide Tranchida René Androsch Holger Schönherr 《Journal of Materials Science》2012,47(7):3040-3045
In this study the effects of crystal habit, crystallinity and superstructure on the modulus of elasticity of isotactic polypropylene
films were analyzed by atomic force microscope (AFM) nanoindentation. The modulus of elasticity, evaluated on the nanometer
scale by AFM, showed a qualitatively similar dependence on the crystal habit, crystallinity and superstructure as the modulus
of elasticity measured by dynamic-mechanical analysis and tensile testing. The observed values of both the surface stiffness
measured by AFM and the macroscopic/bulk stiffness were distinctly larger in the presence of non-isometric lamellae organized
in spherulite than in the presence of isometric nodular crystals, not organized in a spherulitic superstructure. The experimental
data showed that the modulus of elasticity is not primarily influenced by the presence or absence of spherulite but by the
molecular-deformation constraint associated to the crystal habit. 相似文献
54.
This paper describes the measurements and the post-processing procedure adopted for the determination of the turbulence intensity in a low pressure turbine (LPT) by means of a single sensor fast response aerodynamic pressure probe. The rig was designed in cooperation with MTU Aero Engines and considerable efforts were put into the adjustment of all relevant model parameters. Blade count ratio, airfoil aspect ratio, reduced massflow, reduced speed, inlet turbulence intensity and Reynolds numbers were chosen to reproduce the full scale LP turbine. Measurements were performed adopting a phase-locked acquisition technique in order to provide the time resolved flow field downstream of the turbine rotor. The total pressure random fluctuations are obtained by selectively filtering, in the frequency domain, the deterministic unsteadiness due to the rotor blades and coherent structures. The turbulence intensity is derived from the inverse Fourier transform and the correlations between total pressure and velocity fluctuations. The determination of the turbulence intensity allows the discussion of the interaction processes between the stator and rotor for engine-representative operating conditions of the turbine. 相似文献
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Ecofriendly manure anaerobic digestion assisted by soluble bio‐based substances obtained from anaerobic digestion,composting and chemical hydrolysis of urban bio‐wastes. A step toward the integration of urban and agriculture waste management
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58.
Davide Giglio Riccardo Minciardi Simona Sacone Silvia Siri 《Discrete Event Dynamic Systems》2014,24(3):339-352
A class of production systems are considered in this paper with the aim of determining closed-loop strategies providing the production effort as functions of the system state. The key feature of the considered class of systems is that the demand and the way it is satisfied are asynchronous sequences of part requests and instantaneous withdrawals, respectively, generated by discrete-event processes, whereas the production process has continuous-time dynamics. The optimization problem, whose objective is to minimize inventory and lateness costs, is restated as an optimal control problem by exploiting some structural properties of the optimal solution. Then, optimal closed-loop strategies are found with dynamic programming techniques. 相似文献
59.
Antimo Barbato Antonio Capone Giuliana Carello Maurizio Delfanti Davide Falabretti Marco Merlo 《Energy Efficiency》2014,7(6):1013-1052
With the Smart Grid revolution and the increasing interest in renewable energy sources, the management of the electricity consumption and production of individual households and small residential communities is becoming an essential element of new power systems. The electric energy chain can greatly benefit from a flexible interaction with end-users based on the optimization of load profiles and the exploitation of local generation and energy storage. This paper proposes a framework for the development of a complete energy management system for individual residential units and small communities of domestic users, taking into account both the power system and the final users’ perspectives. All the main elements of the framework are considered, and contributions are provided on the users’ habits profiling, electricity generation forecast, energy load, and storage optimization. Specifically, we propose a linear regression model to predict the photovoltaic panels production, a stochastic method to forecast the home appliances usage, and two optimization models to optimize the electricity management of residential users with the goal of minimizing their bills. The study shows that it is possible to reduce the energy bill of residential users through the electricity optimization driven by dynamic energy prices. Moreover, remarkable improvements of the electric grid efficiency can be achieved with the cooperation among users, confirming that services for the coordination of the demand of groups of users allow huge benefits on the power system performance. 相似文献
60.