A Hybrid Evolutionary Algorithm for Efficient Exploration of Online Social Networks

Online social networks provide large amount of valuable data and may serve as research platforms for various social network analysis tools. In this study, we propose a mathematical model for efficient exploration of an online social network. The goal is to spend minimal amount of time searching for characteristics which define a sub-network of users sharing the same interest or having certain common property. We further develop an efficient hybrid method (HEA), based on the combination of an Evolutionary Algorithm (EA) with Local Search procedure (LS). The proposed mathematical model and hybrid method are benchmarked on real-size data set with up to 10 000 users in a considered social network. We provide optimal solutions obtained by CPLEX solver on problem instances with up to 100 users, while larger instances that were out of reach of the CPLEX were efficiently solved by the proposed hybrid method. Presented computational results show that the HEA approach quickly reaches all optimal solutions obtained by CPLEX solver and gives solutions for the largest considered instance in very short CPU time

ON GENERALIZATIONS OF STIRLING NUMBERS AND SOME WELL-KNOWN MATRICES

We introduce a generalization of the Stirling numbers of the first kind and the second kind. By arranging these numbers into matrices, we generalize the Stirling matrices of the first kind and the second kind investigated by Cheon and Kim [Stirling matrix via Pascal matrix, Linear Algebra Appl. 329 (2001) 49–59]. Furthermore, we introduce generalizations of the Pascal matrix and the symmetric Pascal matrix with two real arguments, and generalize earlier results related to the Pascal matrices, Stirling matrices and matrices involving Bell numbers

Poboljšani algoritmi za determinizaciju fazi i težinskih automata

Determinization algorithms are methods that calculate complete deterministic fuzzy (weighted) automaton that is language equivalent to the input fuzzy (weighted) automaton, and they have found application in numerous fields, including lexicographic analysis, analysis of regular expressions, automatic speech recognition, pattern recognition in artificial intelligence, etc. Especially important class of determinization algorithms are canonization algorithms, which produce minimal complete deterministic fuzzy (weighted) automaton equivalent to the input fuzzy (weighted) automaton. The aim of this dissertation is the development of determinization algorithms based on the concept of factorizations, as well as computing and merging of the indistinguishable states of fuzzy (weighted) automaton under construction. At the same time, computing and merging of the indistinguishable states is done by right and left invariant fuzzy relations in the case of fuzzy automata, as well as by right and left invariant Boolean matrices in the case of weighted automata. We apply the partition refinement technique to obtain improved algorithms for computing the greatest right and left invariant Boolean equivalence and quasi – order matrices. In the end, we consider ways to compute the greatest right and left invariant fuzzy equivalences and fuzzy quasi – orders when the algorithms for their computation, based on the partition refinement technique, are unable to stop in a finite number of steps

Approximate State Reduction of Fuzzy Finite Automata

In this paper we introduce a new type of approximate state reductions where the behaviors of the reduced and the original automaton do not have to be identical, but they must match on all words of length less than or equal to some given natural number. We provide four methods for performing such reductions.Comment: In Proceedings AFL 2023, arXiv:2309.0112

Diet supplementation helps honey bee colonies in combat infections by enhancing their hygienic behaviour

The hygienic behavior in honey bees is a complex polygenic trait that serves as a natural defense mechanism against bacterial and fungal brood diseases and Varroa destructor mites infesting brood cells. The aim of this study was to evaluate the effect of a dietary amino acids and vitamins supplement “BEEWELL AminoPlus” on hygienic behavior of Apis mellifera colonies combating microsporidial and viral infections. The experiment was performed during a one-year period on 40 colonies alloted to five groups: one supplemented and infected with Nosema ceranae and four viruses (Deformed wing virus - DWV, Acute bee paralysis virus - ABPV, Chronic bee paralysis virus - CBPV and Sacbrood virus – SBV), three not supplemented, but infected with N. ceranae and/ or viruses, and one negative control group. Beside the l isted pathogens, honey bee trypanosomatids were also monitored in all groups.The supplement “BEEWELL AminoPlus” induced a significant and consistent increase of the hygienic behavior in spite of the negative effects of N. ceranae and viral infections. N. ceranae and viruses significantly and consistently decreased hygienic behavior, but also threatened the survival of bee colonies. The tested supplement showed anti-Nosema effect, since the N. ceranae infection level significantly and consistently declined onl

Oxidative status of honey bees infected with Nosema ceranae microsporidium and supplemented with Agaricus bisporus mushroom extract

Nosema ceranae, a microsporidium species, is among the most common causes of bee diseases. The positive effect of Agaricus bisporus mushroom extract on the survival and immunity of Nosema-infected bees has been reported recently. The effect could be achieved by stimulating the expression of immune-related genes, but also by suppressing nosemosis. The aim of this work was to determine the effect of A. bisporus extract on the oxidative status of bees infected with N. ceranae. In a cage experiment on newly hatched bees, the effect of aqueous extract of champignon (A. bisporus, strain A15) was investigated. Six groups were formed: three groups were infected and received A. bisporus extract through food at different times (days 1, 3, and 6 after hatching), one group received the extract but was not infected (treatment control), one was only infected with Nosema (positive control) and one was neither infected nor received the extract (negative control). The effects were examined on samples taken on days 7 and 15 of the study. The activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST) and the concentrations of malondialdehyde (MDA) were determined. In comparison to the positive control, the enzyme activities and MDA concentrations were significantly lower in the groups fed with the mushroom extract supplement. In the negative control, the level of oxidative stress was lower than in the positive control. In comparison with the other groups, the values mostly did not differ significantly. The oxidative status of bees infected with N. ceranae was significantly better if they were fed with the A. bisporus extract

Depth-Bounded Fuzzy Simulations and Bisimulations between Fuzzy Automata

Simulations and bisimulations are well-established notions in crisp/fuzzy automata theory and are widely used to compare the behaviors of automata. Their main drawback is that they compare the behaviors of fuzzy automata in a crisp manner. Recently, fuzzy simulations and fuzzy bisimulations have been defined for fuzzy automata as a kind of approximate simulations and approximate bisimulations that compare the behaviors of fuzzy automata in a fuzzy manner. However, they still suffer from serious shortcomings. First, they still cannot correlate all fuzzy automata that are intuitively "more or less" (bi)similar. Second, the currently known algorithms for computing the greatest fuzzy simulation or bisimulation between two finite fuzzy automata have an exponential time complexity when the {\L}ukasiewicz or product structure of fuzzy values is used. This work deals with these problems, providing approximations of fuzzy simulations and fuzzy bisimulations. We define such approximations via a novel notion of decreasing sequences of fuzzy relations whose infima are, under some conditions, fuzzy simulations (respectively, bisimulations). We call such a sequence a depth-bounded fuzzy simulation (respectively, bisimulation), as the $n$th element from the sequence compares the behaviors of fuzzy automata, but only for words with a length bounded by $n$. We further provide a logical characterization of the greatest depth-bounded fuzzy simulation or bisimulation between two fuzzy automata by proving that it satisfies the corresponding Hennessy-Milner property. Finally, we provide polynomial-time algorithms for computing the $n$th component of the greatest depth-bounded fuzzy simulation (respectively, bisimulation) between two finite fuzzy automata

Krečni malteri sa dodatkom reciklirane opeke namenjeni za restauraciju istorijskih objekata

U radu su prikazani rezultati ispitivanja fizičko-mehaničkih svojstava krečnih maltera kod kojih je rečni agregat delimično zamenjen agregatom od reciklirane drobljene opeke sa 25, 50 i 75% (zapreminski), pri različitim zapreminskim odnosima kreča i agregata. Ispitivanja su vršena pri starostima od 7, 14, 28 i 56 dana. Čvrstoće pri pritisku pri starosti od 7 dana veće su za malterske mešavine sa dodatkom drobljene opeke u odnosu na referentne mešavine. Najveće vrednosti čvrstoće pri pritisku i adhezije za podlogu ostvarene su kod mešavine sa zapreminskim odnosima komponenata 1:3 i sa 75% učešća agregata od drobljene opeke i iznosile su redom 1,47 MPa i 0,21 MPa