Papers by Tatjana Jakšić Krüger
2022 Fourth International Conference on Blockchain Computing and Applications (BCCA)
We propose Combinatorial Optimization based Consensus Protocol (COCP) that considers efficient us... more We propose Combinatorial Optimization based Consensus Protocol (COCP) that considers efficient use of energy in Blockchain (BC) consensus protocol based on Proof-of-Useful-Work (PoUW) concept. Instead of classical cryptographic puzle, it involves dealing with hard real-life combinatorial optimization (CO) problems submitted by BC participants called customers. Two sources of rewards are provided for miners, one related to adding a new block and the other for solving an instance of CO problem. The main issues that arise when combining BC and CO, are security and consistency of maintaining the whole system. We discuss how to resolve them and what are the benefits of the proposed COCP for all BC participants. Our proposed doubly-rewarding scheme and efficiency in energy exploration are illustrated on a small example from the Ethereum BC network.
Proceedings of the 11th International Conference on Operations Research and Enterprise Systems
Symmetry, Jan 3, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Communications in computer and information science, 2022
Symmetry
Blockchains (BCs) are distributed database systems, popular for their innovative, unsupervised ma... more Blockchains (BCs) are distributed database systems, popular for their innovative, unsupervised maintenance process. They use a so-called consensus protocol to prevent inference by any third party of absolute trust. Security, privacy, consistency, and energy consumption have been identified as the main issues involved in BC maintenance. According to the recent literature, some of these issues can be formulated as combinatorial optimization (CO) problems, and this fact motivated us to consider incorporating CO approaches into a BC. In this paper, we propose the new combinatorial optimization consensus protocol (COCP) based on the proof-of-useful-work (PoUW) concept that assumes solving instances of real-life CO problems. Due to the complexity of the underlying CO problems, we have developed various types of heuristic methods, which are utilized in the COCP. Most of these methods are problem-dependent stochastic heuristic or metaheuristic methods. As is the case with the majority of co...
Proceedings of the 11th International Conference on Operations Research and Enterprise Systems, 2022
International Journal of Bio-Inspired Computation, 2016
ABSTRACT The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method f... more ABSTRACT The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method for dealing with hard, real-life combinatorial and continuous optimization problems. It is based on the foraging habits of honeybees and was proposed by Lucic and Teodorovic in 2001. BCO is a simple, but efective meta-heuristic method that has already been successfully applied to various combinatorial optimization problems in transport, location analysis, scheduling and some other fields. This paper provides theoretical verification of the BCO algorithm by proving some convergence properties. As a result, the gap between successful practice and missing theory is reduced.
Mape gravitacionih mikrosočiva su matrice čiji elementi predstavlju vrednosti pojačanja intezitet... more Mape gravitacionih mikrosočiva su matrice čiji elementi predstavlju vrednosti pojačanja inteziteta svetlosti koja se kreće ka nama iz nekog udaljenog pozadinskog izvora. Ove mape se generišu na osnovu slučajnog rasporeda zvezda u ravni sočiva od kojih svaka pojačava svetlost emitovanu iz pozadinskog izvora i savija je pod odredjenim uglom (Jovanović et al 2008). Program za generisanje mapa gravitacionih mikrosočiva, namenjen za izvršavanje na jednoprocesorskim računarima, za odredjene vrednosti ulaznih parametara zahteva puno procesorskog vremena. Zahvaljujući medjusobno nezavisnim računarskim delovima programa, a pomoću biblioteke za prosledjivanje poruka MPI (Message Passing Interface), program je modifikovan za paralelno izvršavanje na klasteru Matematičkog Instituta Srpske Akademije Nauka i Umetnosti (SANU) i tako značajno ubrzan proces generisanja mapa gravitacionih mikrosočiva (Quinn, 2003). Ovim je postignuto ubrzanje od 10 do 40 puta, u zavisnosti od veličine mape i vrednosti...
The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method for dealin... more The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method for dealing with hard, real-life optimization problems. It is based on the foraging habits of honeybees and was proposed by Lučić and Teodorović in 2001. Through numerous applications in transportation, location theory, scheduling and some other fields, method has evolved and underwent many transformations, modifications, even parallelization, which resulted in the increase of its efficiency. The first results of the theoretical verification of the BCO method have appeared recently. The aim of this paper is to further contribute to this topic.
The plate archives of the Belgrade Astronomical Observatory contain more than 15000 glass photogr... more The plate archives of the Belgrade Astronomical Observatory contain more than 15000 glass photographic plates from the period 1936-1996. In addition to the other equipment the Observatory disposed of four instruments devoted especially to astrophotographic observations: Zeiss Refractor 65/1055 cm with special camera, Zeiss Astrograph 16/80 cm, Zeiss Refractor 20/302 cm with two photographic cameras 16/80 cm and Askania Equatorial refractor 13.5/100 cm. Scientific observations were performed in the framework of the programs like: minor planet follow-up, search for the new objects (33 new minor planets were discovered from BAO), comet investigation, systematic observations of the Sun, Moon, giant planets, natural and artifical satellites, variable stars, double and multiple stars, stellar clusters, etc. Rare phenomena, such as passages of Mercury and Venus across the solar disc, lunar occultations of stars and planets and special objects have been observed too. The current status of B...
Scientometrics, 2014
Digital preservation of scientific papers enables their wider accessibility, but also provides a ... more Digital preservation of scientific papers enables their wider accessibility, but also provides a valuable source of information that can be used in a longitudinal scientometric study. The Electronic Library of the Mathematical Institute of the Serbian Academy of Sciences and Arts (eLib) digitizes the most prominent mathematical journals printed in Serbia. In this paper, we study a co-authorship network which represents collaborations among authors who published their papers in the eLib journals in an 80 year period (from 1932 to 2011). Such study enables us to identify patterns and long-term trends in scientific collaborations that are characteristic for a community which mainly consists of Serbian (Yugoslav) mathematicians. Analysis of connected components of the network reveals a topological diversity in the network structure: the network contains a large number of components whose sizes obey a power-law, the majority of components are isolated authors or small trivial components, but there is also a small number of relatively large, non-trivial components of connected authors. Our evolutionary analysis shows that the evolution of the network can be divided into six periods that are characterized by different intensity and type of collaborative behavior among eLib authors. Analysis of author metrics shows that betweenness centrality is a better indicator of author productivity and long-term presence in the eLib journals than degree centrality. Moreover, the strength of correlation between productivity metrics and betweenness centrality increases as the network evolves suggesting that even more stronger correlation can be expected in the future.
Optimization, 2013
ABSTRACT The Bee Colony Optimization (BCO) algorithm is a meta-heuristic that belongs to the clas... more ABSTRACT The Bee Colony Optimization (BCO) algorithm is a meta-heuristic that belongs to the class of biologically inspired stochastic swarm optimization methods, based on the foraging habits of bees in nature. BCO operates on a population of solutions, and therefore, it represents a good basis for parallelization. The main contribution of this work is the development of new and efficient parallelization strategies for BCO. We propose two synchronous and two asynchronous parallelization strategies for a distributed memory multiprocessor architecture under the Message Passing Interface (MPI) communication protocol. The first synchronous strategy involves independent execution of several BCO algorithms, while the second one implements cooperation between these algorithms. The asynchronous strategies are implemented in two ways: with centralized and non-centralized communication controls. The presented experimental results, addressing the problem of static scheduling independent tasks on identical machines, show that our parallel BCO algorithms provide excellent performance. As for the case of independent execution, a significant speedup is obtained while preserving the solution quality. Compared to the sequential execution, cooperative strategy leads to better quality solutions within the same amount of wall-clock time, as long as it is applied to a modest number of processors engaged in parallel BCO execution. As this number increases, asynchronous strategies outperform the other ones with respect to both solution quality and running time.
Proceedings of the …, 2006
Универзитет у Новом Саду, Jun 27, 2017
Intensive applications and success of metaheuristics in practice have initiated research on their... more Intensive applications and success of metaheuristics in practice have initiated research on their theoretical analysis. Due to the unknown quality of reported solution(s) and the inherently stochastic nature of metaheuristics, the theoretical analysis of their asymptotic convergence towards a global optimum is mainly conducted by means of probability theory. In this paper, we show that principles developed for the theoretical analysis of Bee Colony Optimization metaheuristic hold for swarm intelligence based metaheuristics: they need to implement learning mechanisms in order to properly adapt the probability rule for modification of a candidate solution. We propose selection schemes that a swarm intelligence based metaheuristic needs to incorporate in order to assure the so-called model convergence.
The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method for dealin... more The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method for dealing with hard, real-life optimization problems. It is based on the foraging habits of honeybees and was proposed by Lučić and Teodorović in 2001. Through numerous applications in transportation, location theory, scheduling and some other fields, method has evolved and underwent many transformations, modifications, even parallelization, which resulted in the increase of its efficiency. The first results of the theoretical verification of the BCO method have appeared recently. The aim of this paper is to further contribute to this topic.
Bee Colony Optimization (BCO) is a nature-inspired population-based meta-heuristic method that be... more Bee Colony Optimization (BCO) is a nature-inspired population-based meta-heuristic method that belongs to the class of Swarm intelligence algorithms. BCO was proposed by Lučić and Teodorović, who were among the first to use the basic principles of collective bee intelligence in dealing with optimization problems. Designing a BCO method in principle includes choosing a procedure for constructive/improvement moves, an evaluation function and setting BCO parameters to a suitable values. Topic of this work is addressing the influence of right choice of BCO underlying procedures, such as the choice of loyalty functions, and influence of parameter variations on algorithm performance, by means of visual inspection. Analyses were conducted for simple variant of scheduling problem. Also, to achieve good alternatives for reported solutions, new evaluation methods for scheduling problem are presented.
Advances in Intelligent Systems and Computing, 2015
ABSTRACT Digital libraries enable worldwide access to scientific results, but also provide a valu... more ABSTRACT Digital libraries enable worldwide access to scientific results, but also provide a valuable source of information that can be used to investigate patterns and trends in scientific collaboration. The Electronic Library of the Mathematical Institute of the Serbian Academy of Sciences and Arts (eLib) digitizes the most prominent mathematical journals printed in Serbia. Using eLib bibliographical records we constructed a co-authorship network representing collaborations between authors who published their papers in eLib journals in the period from 1932 to 2011. In this paper we apply community detection techniques in order to examine the structure of the eLib co-authorship network. Such study reveals characteristic patterns of scientific collaboration in Serbian mathematical journals, and helps us to understand the (self-)organization of the eLib community of authors.
The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method for dealin... more The Bee Colony Optimization (BCO) algorithm is a nature-inspired meta-heuristic method for dealing with hard, real-life optimization problems. It is based on the foraging habits of honeybees and was proposed by Lučić and Teodorović in 2001. Through numerous applications in transportation, location theory, scheduling and some other fields, method has evolved and underwent many transformations, modifications, even parallelization, which resulted in the increase of its efficiency. The first results of the theoretical verification of the BCO method have appeared recently. The aim of this paper is to further contribute to this topic.
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Papers by Tatjana Jakšić Krüger