35,895 research outputs found
Nominal Logic with Equations Only
Many formal systems, particularly in computer science, may be captured by
equations modulated by side conditions asserting the "freshness of names";
these can be reasoned about with Nominal Equational Logic (NEL). Like most
logics of this sort NEL employs this notion of freshness as a first class
logical connective. However, this can become inconvenient when attempting to
translate results from standard equational logic to the nominal setting. This
paper presents proof rules for a logic whose only connectives are equations,
which we call Nominal Equation-only Logic (NEoL). We prove that NEoL is just as
expressive as NEL. We then give a simple description of equality in the empty
NEoL-theory, then extend that result to describe freshness in the empty
NEL-theory.Comment: In Proceedings LFMTP 2011, arXiv:1110.668
Nominal C-Unification
Nominal unification is an extension of first-order unification that takes
into account the \alpha-equivalence relation generated by binding operators,
following the nominal approach. We propose a sound and complete procedure for
nominal unification with commutative operators, or nominal C-unification for
short, which has been formalised in Coq. The procedure transforms nominal
C-unification problems into simpler (finite families) of fixpoint problems,
whose solutions can be generated by algebraic techniques on combinatorics of
permutations.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
Hydrogen vs. Battery in the long-term operation. A comparative between energy management strategies for hybrid renewable microgrids
The growth of the world’s energy demand over recent decades in relation to energy intensity and demography is clear. At the same time, the use of renewable energy sources is pursued to address decarbonization targets, but the stochasticity of renewable energy systems produces an increasing need for management systems to supply such energy volume while guaranteeing, at the same time, the security and reliability of the microgrids. Locally distributed energy storage systems (ESS) may provide the capacity to temporarily decouple production and demand. In this sense, the most implemented ESS in local energy districts are small–medium-scale electrochemical batteries. However, hydrogen systems are viable for storing larger energy quantities thanks to its intrinsic high mass-energy density. To match generation, demand and storage, energy management systems (EMSs) become crucial. This paper compares two strategies for an energy management system based on hydrogen-priority vs. battery-priority for the operation of a hybrid renewable microgrid. The overall performance of the two mentioned strategies is compared in the long-term operation via a set of evaluation parameters defined by the unmet load, storage efficiency, operating hours and cumulative energy. The results show that the hydrogen-priority strategy allows the microgrid to be led towards island operation because it saves a higher amount of energy, while the battery-priority strategy reduces the energy efficiency in the storage round trip. The main contribution of this work lies in the demonstration that conventional EMS for microgrids’ operation based on battery-priority strategy should turn into hydrogen-priority to keep the reliability and independence of the microgrid in the long-term operation
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