Network based data oriented methods for application driven problems

Networks are amazing. If you think about it, some of them can be found in almost every single aspect of our life from sociological, financial and biological processes to the human body. Even considering entities that are not necessarily connected to each other in a natural sense, can be connected based on real life properties, creating a whole new aspect to express knowledge. A network as a structure implies not only interesting and complex mathematical questions, but the possibility to extract hidden and additional information from real life data. The data that is one of the most valuable resources of this century. The different activities of the society and the underlying processes produces a huge amount of data, which can be available for us due to the technological knowledge and tools we have nowadays. Nevertheless, the data without the contained knowledge does not represent value, thus the main focus in the last decade is to generate or extract information and knowledge from the data. Consequently, data analytics and science, as well as data-driven methodologies have become leading research fields both in scientific and industrial areas. In this dissertation, the author introduces efficient algorithms to solve application oriented optimization and data analysis tasks built on network science based models. The main idea is to connect these problems along graph based approaches, from virus modelling on an existing system through understanding the spreading mechanism of an infection/influence and maximize or minimize the effect, to financial applications, such as fraud detection or cost optimization in a case of employee rostering

Networks in the mind – what communities reveal about the structure of the lexicon

The mental lexicon stores words and information about words. The lexicon is seen by many researchers as a network, where lexical units are nodes and the different links between the units are connections. Based on the analysis of a word association network, in this article we show that different kinds of associative connections exist in the mental lexicon. Our analysis is based on a word association database from the agglutinative language Hungarian. We use communities – closely knit groups – of the lexicon to provide evidence for the existence and coexistence of different connections. We search for communities in the database using two different algorithms, enabling us to see the overlapping (a word belongs to multiple communities) and non-overlapping (a word belongs to only one community) community structures. Our results show that the network of the lexicon is organized by semantic, phonetic, syntactic and grammatical connections, but encyclopedic knowledge and individual experiences are also shaping the associative structure. We also show that words may be connected not just by one, but more types of connections at the same time

Brands, networks, communities: How brand names are wired in the mind

Brands can be defined as psychological constructs residing in our minds. By analyzing brand associations, we can study the mental constructs around them. In this paper, we study brands as parts of an associative network based on a word association database. We explore the communities–closely-knit groups in the mind–around brand names in this structure using two community detection algorithms in the Hungarian word association database ConnectYourMind. We identify brand names inside the communities of a word association network and explain why these brand names are part of the community. Several detected communities contain brand names from the same product category, and the words in these categories were connected either to brands in the category or to words describing the product category. Based on our findings, we describe the mental position of brand names. We show that brand knowledge, product knowledge and real word knowledge interact with each other. We also show how the meaning of a product category arises and how this meaning is related to brand meaning. Our results suggest that words sharing the same community with brand names can be used in brand communication and brand positioning

On a correlational clustering of integers

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Gyakorló orvosok egészségnyereség társadalmi elosztásával kapcsolatos attitűdje – a Q-vizsgálat

Gyakorló orvosok egészségnyereség társadalmi elosztásával kapcsolatos attitűdje – a Q-vizsgálat »»» A tanulmány a kvalitatív kutatás egyik eszközét, a Q-módszert mutatja be, amely lehetőséget teremt adott témával kapcsolatos személyes vélemények megismerésére, a véleménykülönbségek feltárására. Az eljárás során az adatgyűjtés és az adatelemzés kvantitatív módon történik, az elemzés korrelációszámításra, illetve faktoranalízisre támaszkodik, de kis esetszámú minta bevonásával végezhető

Szelektív szintézismódszerek kifejlesztése vizes közegben átmenetifém-komplexek jelenlétében = Development of selective synthetic methods in aqueous medium in the presence os transition metal complexes

Kutatómunkánkat króm(II) komplexek szelektív szintézisreakcióinak fejlesztésén végeztük. Kidolgoztuk a Nozaki-Hiyama reakció szén-szén kötések enantioszelektív kialakítására alkalmas módszerét karbonil- és halogénszármazékok kapcsolásában, króm(II) komplexek jelenlétében. Tanulmányoztuk szénhidrátszármazékok anomer centrumának reaktivitását CrIIEDTA komplex jelenlétében, semleges-vizes közegben és új módszereket dolgoztunk ki glikálok és C-glikozidok előállítására. Természetes aminosavak króm(II) komplexeinek királis információját aminok enantioszelektív szintézisére alkalmaztuk. Tanulmányoztuk az enantioszelektív autokatalízis törvényszerűségeit, empirikus összefüggést dolgoztunk ki a királis erősítés jellemzésére. | Selective synthetic reactions could be developed in our research work in the present of chromium(II) complexes. The Nozaki-Hiyama reaction could be developed for enantioselective carbon-carbon coupling in the reactions of carbonyl- and halogen derivatives using chromium(II) complexes. Reactivity of the anomeric centre of carbohydrate derivatives was investigated with CrIIEDTA complex in neutral aqueous medium and new methods could be developed for preparation of glycals and C-glycosides. Amino acid induced enantioselective amine synthesis could be developed in the presence of Cr(II) in aqueous medium. The principles of the enantioselective autocatalytic reactions could be investigated and empirical relation proposed for the chiral amplification

Evaluating the role of community detection in improving influence maximization heuristics

Both community detection and influence maximization are well-researched fields of network science. Here, we investigate how several popular community detection algorithms can be used as part of a heuristic approach to influence maximization. The heuristic is based on the community value, a node-based metric defined on the outputs of overlapping community detection algorithms. This metric is used to select nodes as high influence candidates for expanding the set of influential nodes. Our aim in this paper is twofold. First, we evaluate the performance of eight frequently used overlapping community detection algorithms on this specific task to show how much improvement can be gained compared to the originally proposed method of Kempe et al. Second, selecting the community detection algorithm(s) with the best performance, we propose a variant of the influence maximization heuristic with significantly reduced runtime, at the cost of slightly reduced quality of the output. We use both artificial benchmarks and real-life networks to evaluate the performance of our approach

Gateway placement and traffic load simulation in sensor networks

Because of the wide variety of possible application fields and the spread of smart devices, the research of wireless sensor networks has become an increasingly important area in the last decade. During the design of these networks, several important aspects have to be considered, for example the lifetime of the network, expected battery usage, or robustness of the installed system. In this paper a simulation environment is introduced that enables the testing of different information spreading methods on the network and provides suggestions for gateway placements with different objectives