Search results for " Minimization"
showing 10 items of 107 documents
Extremal minimality conditions on automata
2012
AbstractIn this paper we investigate the minimality problem of DFAs by varying the set of final states. In other words, we are interested on how the choice of the final states can affect the minimality of the automata. The state-pair graph is a useful tool to investigate such a problem. The choice of a set of final states for the automaton A defines a coloring of the closed components of the state-pair graph and the minimality of A corresponds to a property of these colored components. A particular attention is devoted to the analysis of some extremal cases such as, for example, the automata that are minimal for any choice of the subset of final states F from the state set Q of the automato…
Automata with Extremal Minimality Conditions
2010
It is well known that the minimality of a deterministic finite automaton (DFA) depends on the set of final states. In this paper we study the minimality of a strongly connected DFA by varying the set of final states. We consider, in particular, some extremal cases. A strongly connected DFA is called uniformly minimal if it is minimal, for any choice of the set of final states. It is called never-minimal if it is not minimal, for any choice of the set of final states. We show that there exists an infinite family of uniformly minimal automata and that there exists an infinite family of never-minimal automata. Some properties of these automata are investigated and, in particular, we consider t…
Nondeterministic Moore Automata and Brzozowski’s Algorithm
2011
Moore automata represent a model that has many applications. In this paper we define a notion of coherent nondeterministic Moore automaton (NMA) and show that such a model has the same computational power of the classical deterministic Moore automaton. We consider also the problem of constructing the minimal deterministic Moore automaton equivalent to a given NMA. In this paper we propose an algorithm that is a variant of Brzozowski's algorithm in the sense that it is essentially structured as reverse operation and subset construction performed twice.
On Extremal Cases of Hopcroft’s Algorithm
2009
In this paper we consider the problem of minimization of deterministic finite automata (DFA) with reference to Hopcroft’s algorithm. Hopcroft’s algorithm has several degrees of freedom, so there can exist different sequences of refinements of the set of the states that lead to the final partition. We find an infinite family of binary automata for which such a process is unique. Some recent papers (cf. [3,7,1]) have been devoted to find families of automata for which Hopcroft’s algorithm has its worst execution time. They are unary automata associated to circular words. However, automata minimization can be achieved also in linear time when the alphabet has only one letter (cf. [14]), so in …
Perturbative treatment of triple excitations in internally contracted multireference coupled cluster theory.
2012
Internally contracted multireference coupled cluster (ic-MRCC) methods with perturbative treatment of triple excitations are formulated based on Dyall's definition of a zeroth-order Hamiltonian. The iterative models ic-MRCCSDT-1, ic-MRCC3, and their variants ic-MRCCSD(T), ic-MRCC(3) which determine the energy correction from triples by a non-iterative step are consistent in the single-reference limit with CCSDT-1a, CC3, CCSD(T), and CC(3), respectively. Numerical tests on the potential energy surfaces of BeH(2), H(2)O, and N(2) as well as on the structure and harmonic vibrational frequencies of the ozone molecule show that these methods account very well for higher order correlation effects…
Experimental investigation on high efficiency real-time control algorithms for IPMSMs
2014
This paper describes an experimental investigation on the power losses variations occurring in an Interior Permanent Magnet Synchronous Motor (IPMSM) with respect to the direct axis current component. Such investigation can be useful to determine a mathematical model accounting for copper, iron and mechanical friction losses, and for the arrangement of a speed control drive system equipped with a real-time power losses minimization algorithm. In particular, a test bench has been set up in order to carry out all measurements and the final power loss identification. The test bed is composed by a IPMSM drive with a field oriented control (FOC) strategy, a power analyzer, a dynamometric brake a…
Experimental study on efficiency enhancement in Interior Permanent Magnet Synchronous machines
2015
This paper presents an experimental study on the efficiency variation occurring in an IPMSM (Interior Permanent Magnet Synchronous Motor) with respect to the direct axis current component and for several working conditions. Such investigation is the starting point for the arrangement of a speed control drive system equipped with a real-time power losses minimization algorithm. More in detail, a test bench is set up to carry out the measurements needed for the final power loss identification. The experimental investigation is developed by performing tests at different speed, magnetization and load conditions. From the obtained results, it can be stated that the IPMSM efficiency can be maximi…
Optimum Performance of Permanent Magnet Synchronous Generators Coupled to Wind Turbines
2007
In this paper a control algorithm for the efficiency improvement of permanent magnet synchronous generators (PMSG) is presented. The proposed algorithm reduces the losses of the generator without affecting its performances. In details, after a description of a dynamic model of the PMSG, which has been purposely modified in order to take into account the iron losses, the basic equations and the constraints to obtain the loss minimization are presented and discussed. Some simulations of a specific PMSG employing the proposed algorithm are performed. The results of these simulations show that enhancement of the efficiency up to 3% can be reached in comparison to a PMSG using a traditional cont…
Efficiency Maximization of Permanent Magnet Synchronous Generators Coupled to Wind Turbines
2007
In this paper a control algorithm for the efficiency improvement of permanent magnet synchronous generators (PMSG), the relative simulations and their results are presented. The proposed algorithm reduces the losses of the generator without affecting its performances. In details, after a description of a dynamic model of the PMSG, which has been modified in order to take into account the iron losses, the basic methodologies to obtain the loss minimization are presented and discussed. Many simulations of a specific PMSG employing the proposed algorithm were carried out and are presented. The results of these simulations show that enhancement of the efficiency up to 3% and more can be reached…
Insights on mechanisms of excess sludge minimization in an oxic-settling-anaerobic process under different operating conditions and plant configurati…
2022
In the present research, insights about the mechanisms of excess sludge minimization occurring in an oxic-settling-anaerobic (OSA) were provided. The investigation involved two systems operating in parallel. In particular, a conventional activated sludge (CAS) system as control and a system implementing the OSA process both having a pre-denitrification scheme were considered. Five periods (P1-P5) were studied, during which several operating conditions and configurations were tested. Specifically, the hydraulic retention time (HRT) in the anaerobic reactor of the OSA system (P1 8 h, P2-P3 12 h, P4 8 h, P5 12 h) and the return sludge from the anaerobic to the anoxic (scheme A) (P1-P2) or aero…