11. Automatic reconstruction of complex dynamical networksMarc Grau Leguia, 2019 Abstract: A foremost problem in network science is how to reconstruct (infer) the topology of a real network from signals measured from its internal units. Grasping the architecture of complex networks is key, not only to understand their functioning, but also to predict and control their behaviour. Currently available methods largely focus on the detection of links of undirected networks and often require strong assumptions about the system. However, many of these methods cannot be applied to networks with directional connections. To address this problem, in this doctoral work we focus at the inference of directed networks. Specifically, we develop a model-based network reconstruction method that combines statistics of derivative-variable correlations with simulated annealing. We furthermore develop a data-driven reconstruction method based on a nonlinear interdependence measure.
This method allows one to infer the topology of directed networks of chaotic Lorenz oscillators for a subrange of the coupling strength and link density. Finally, we apply the data-driven method to multichannel electroencephalographic recordings from an epilepsy patient. The functional brain networks obtained from this approach are consistent with the available medical information. Found in: osebi Keywords: network reconstruction, simulated annealing, dynamical systems, nonlinear interdependence measure, EEG Published: 19.04.2019; Views: 2433; Downloads: 144 Fulltext (6,96 MB) |
12. Outstanding problems in nonequilibrium statistical physicsMarco Faggian, 2019 Abstract: This PhD thesis is mainly devoted to the study of different problems in nonequilibrium systems that undergo certain phase transitions. The first part of this thesis constitutes a brief review of fundamental concepts in statistical
physics. Many of them, of course, will be useful in the remaining of the thesis. My research is thus articulated in three main chapters. The second chapter focuses on a numerical and experimental evidence of an absorbing phase
transition, so far associated with spatiotemporal dynamics provided in a purely temporal optical system. We provide a numerical and experimental study of an effective model for a bistable semiconductor laser, with long-delayed opto-electronic feedback and multiplicative noise showing the peculiar features of a critical phenomenon belonging to the directed percolation universality class.
In the third part of the thesis we present a random network of heterogeneous phase oscillators in which the links mediating the interactions are constantly rearranged with a characteristic timescale and an extremely low instantaneous connectivity. We will show that, provided strong coupling and fast enough rewiring are considered, the network is able to reach partial synchronisation even in the vanishing connectivity limit. The last part is dedicated to a systematic test of an effective thermodynamics approach proposed for the identification of critical phase transitions in nonequilibrium systems by making a formal analogy with equilibrium systems. When the authors apply it to experimental data of neurons, this method seems to bring a signature of a "special critical point". However, the approach has never been tested on synthetic data and for this reason we will test it on out of equilibrium toy models that display critical transition in a known range of parameters. In the concluding section I summarise and briefly comment my main results and sketch some directions for further research. Found in: osebi Keywords: statistična fizika, ravnotežna statistična fizika, neenakomerna statistična fizika, termodinamika, kritični pojavi, kritična točka, Kuramoto model, skupina za renormalizacijo, samoorganizirana kritičnost omrežja, Zipfov zakon, efektivni termodinamični pristop Published: 28.05.2019; Views: 2600; Downloads: 155 Fulltext (14,36 MB) |
13. Podatkovna analiza političnega diskurza predsednikov Republike SlovenijeElvira Žagar, 2019 Abstract: Magistrska naloga obsega podatkovno analizo političnega diskurza predsednikov Republike Slovenije. Zajema inavguralne govore, združene govore ob slovesnosti ob Dnevu državnosti ter govore ob zaključku predsedniškega mandata; od prvega govora, ki ga je leta 1991 imel Milan Kučan, ter do zadnjega inavguracijskega govora iz leta 2017, sedanjega predsednika Boruta Pahorja. Magistrska naloga je empirično zastavljena, saj obsega podatkovno analizo korpusov govorov z namenom ugotavljanja frekventnosti pojavljanja določenih besed za ugotavljanje trenutnega stanja v državi skozi spremembe v političnem diskurzu in ugotavljanje retoričnega načina prepričevanja množic. Found in: osebi Keywords: inavguracijski govor, analiza inavguracijskih govorov, analiza političnega diskurza, podatkovna analiza, politični diskurz Published: 13.11.2019; Views: 2377; Downloads: 173 Fulltext (1,96 MB) |
14. Modelling human cardiorespiratory system through heart-rate variabilityAlbert Zorko, 2020 Abstract: The modern computer resources and the data analysis methods allow for a biomedical data to be examined in a more detail than ever. The heart rate variability (HRV) is an easily accessible vital signal that offers a range of useful information about the person under a study. One such application regards an automatical determining whether a person is awake or asleep from the HRV data only. This is of an importance not just for medical but also for practical applications, such as a traffic safety or smart homes.
In this doctoral work we study the HRV data of 75 healthy individuals of a varying age and sex, recorded with a microsecond precision. We employ the empirical fact that heart and respiration cycles couples differently during a sleep and awake period. Namely, a respiratory modulation of a heart rhythm or a respiratory sinus arrhythmia (RSA) is more pronounced while asleep, as both sleep and RSA are connected to a strong vagal activity. Therefore, the onset of sleep can be recognized or perhaps even predicted by a carefully examining the cardio-respiratory coupling. We show that the above can indeed be used, at least in principle, to design an algorithmic method to automatically determine the state of a person's consciousness from the HRV data only.
On the methodological front we rely on quantifying the (self)similarity among the shapelets, the short chunks of the HRV time series, that allow for a consistent comparison among and within the time series. To establish a better benchmark, we also carry out a comprehensive analysis of the overall HRV dynamics depending on age and sex.
Our results include: (i) that a distinctive patterns of the HRV dynamics are consistent across age and sex, (ii) that they are not only an indicative of sleep and awake, but allow to pinpoint the change from awake to sleep and vice versa almost immediately, (iii) that the shapelet analysis is a viable tool to examine these data with a great precision. We conclude that a more systematic analysis involving more subjects could lead to a practical method for the prediction of the onset of sleep. Found in: osebi Keywords: algoritem, EKG, Holter, vzorčna entropija, razmerje signal-šum, klasifikacija Published: 18.09.2020; Views: 2224; Downloads: 218 Fulltext (5,09 MB) |
15. Analiza družabnega omrežja Twitter v času pandemije COVID-19Tomaž Gorenc, 2021 Abstract: Pandemija covid-19 je spremenila svet. Za zajezitev okužb smo večino časa preživeli po svojih domovih, opravljali delo od doma, se šolali na daljavo, veliko več smo se rekreirali in hodili samo po nujnih opravkih. Ker smo bili več časa doma, smo imeli več prostega časa. Posledično smo preživeli več časa na družabnih omrežjih, kjer so se začele pojavljati poleg preverjenih informacij tudi nepreverjene informacije, govorice in zarote. Tako se je poleg obstoječe pandemije pojavila še t. i. »infodemija« in je zajezitev le-te postalo skoraj enako pomembno kot zajezitev same pandemije. V sklopu magistrske naloge smo analizirali družabno omrežje Twitter, tako da smo zbrali in analizirali slovenske tvite, povezane s pandemijo covid-19 z uporabo programskega jezika Python. Proučevali smo vpliv pandemije na Twitter in kaj Slovence najbolj skrbi v povezavi s pandemijo. Found in: osebi Keywords: COVID-19, pandemija, Twitter, družabna omrežja, infodemija Published: 17.03.2022; Views: 1651; Downloads: 78 Fulltext (5,02 MB) |
16. The role of transnational value chains in regional innovation. Analysis of Central and Eastern European regions engaged in automotive and electronics production networksCristian Gangaliuc, 2022 Abstract: The thesis touches on important concepts of innovation and regional development. Their
empirical relevance for economic and social growth is a subject of active debate. Studies
revealed that interactions have a major impact, de facto, on the capacity to innovate.
Diversifying knowledge sources, joint ventures and co-creational practices can explain much
of the locational factors and innovation in a-spatial networks. With the rise of globalisation,
scholars found that Multinational Corporations and their global production chains are
integrating more and more into regions worldwide. They share practices and engage local
stakeholders in their innovation projects. This research aims to explore the importance of
locational and global factors in this process. The goal is to see how these two forces contribute
to innovation separately and when intertwined regionally, closing the gap between regional and
global innovation frameworks.
The thesis contributes to science by developing a new synthesis model based on mainstream
Innovation theories. It includes the endogenous and exogenous forces that create environmental
pressures and opportunities, pushing economic agents to innovate. The central aspect of this
model is the acknowledgement of the multiscalar nature of innovation. Local institutions,
mindsets and influence from the production chains create conditions and pressures in the
network, which motivates companies to innovate. Depending on the local competencies and the
needs of production networks, it creates various environments for companies. It is up to
enterprises to use created opportunities, which can be local, national or global.
Data collected in eight (distinct) regions in Central and Eastern Europe (active in automotive
and electronics industries) was used in qualitative and logical analysis to observe patterns in
regional behaviour. The results revealed that endogenous and exogenous forces act
circumstantially in each region, partially proving all the hypotheses on endogenous and
exogenous factors and validating the model. Each region displays different rates of local and
regional engagement and, thus, different patterns of innovation, determining their competitive
potential. The research also revealed additional factors (e.g., the importance of trust,
particularities of information diffusion, etc.) relevant to innovation in Central and Eastern
Europe. Found in: osebi Keywords: innovation, regional development, transnational value chains, networks, institutions, cognitive mindset, regional-global co-operation Published: 25.10.2022; Views: 666; Downloads: 72 Fulltext (5,96 MB) |
17. The dynamic of employee population of different characteristics in principal - agent model based relationship with employerMirko Talajić, 2022 Abstract: V današnjem času je dinamika sprememb takšna, da moramo najti inovativne in kreativne načine za obvladovanje sprememb, a se tudi prilagajati pogostosti teh sprememb. Dinamika sprememb v vedenju ljudi, njihovem odnosu do dela in kaj jih motivira, so postale glavne preokupacije vodilnih v organizaciji, ki se zavedajo, da kakovostno vodenje ljudi in njihova motivacija naredijo organizacijo učinkovitejšo in nenazadnje uspešnejšo na trgu. Ključno je zavedanje, da strategija upravljanja z ljudmi ne more biti enaka za vse, ampak jo je treba prilagoditi različnim vrstam zaposlenih. Zato so v doktorski disertaciji vsi zaposleni v organizaciji razdeljeni na tri tipe, ki so si vsi homogeni po stopnji zavzetosti za organizacijo, odnosu do dela in motivaciji. Z definiranjem funkcij uporabnosti in plačila za vsako vrsto zaposlenih se modelira vedenje vsake vrste skozi čas (dolgoročno in kratkoročno). Proces modeliranja in analize rezultatov je podprt z uporabo osnovnih principov teorije iger, evolucijske teorije iger in dinamike replikatorja. Dobljeni rezultati kažejo, da se lahko organizacija, če pozna izhodiščno populacijsko strukturo svojih zaposlenih, pravočasno odloči in usmeri gibanje strukture k želenemu stabilnemu stanju, kjer so stroški optimalni. Razvit metodološki okvir odpira številne možnosti, vključno z dodajanjem novih spremenljivk, za razširitev modela, kar posledično odpira možnost podrobnejših analiz in konkretnejših usmeritev pri sprejemanju še boljših odločitev, ki se odražajo v boljših organizacijskih rezultatih. Found in: osebi Keywords: principal - agent model, evolucijsko stabilne strategije, replikatorska dinamika, tip zaposlenega, zavzetost Published: 25.04.2023; Views: 633; Downloads: 39 Fulltext (3,45 MB) |
18. Statistična analiza pogostosti potresov na svetovni ravniJernej Žagar, 2023 Abstract: Magistrska naloga vsebuje statistično analizo pogostosti potresov v svetovnem merilu. V nalogi
predstavimo zbiranje podatkov o potresnih dejavnostih, ki se nahajajo na spletni strani ameriške
znanstvene agencije. Z uporabo programskega jezika Python zbrane podatke očistimo, jih
analiziramo in predstavimo grafično. Z uporabo knjižnice GeoPandas posamezne lokacije
potresov prestavimo tudi na zemljevidu. Za vodilo analize uporabimo zastavljene hipoteze s
katerimi skušamo preveriti korelacijo med magnitudo, globino, posamezno lokacijo in časovno
komponento potresov. Pri tem se osredotočimo na potresno zanimive lokacije, obravnavamo
tudi Slovenijo. Found in: osebi Keywords: potresi, seizmologija, analiza velikih količin podatkov, magnituda, globina, gručenje Published: 19.07.2023; Views: 623; Downloads: 76 Fulltext (3,83 MB) |
19. Uporaba Google Apps v manjšem gradbenem in računovodskem podjetjuNatalija Zoran, 2013 Abstract: Računalništvo v oblaku (angl. Cloud Computing) je nova računalniška storitveno orientirana paradigma, pri kateri uporabniki dostopajo do zahtevnejših računalniških virov. Google ponuja paket omenjenih spletnih storitev pod imenom Google Apps (GApps), ki omogoča lažje in varnejše delo v skupinah z različnimi spletnimi produkti.
V diplomski nalogi smo predstavili koncept računalništva v oblaku, njegove značilnosti ter prednosti in slabosti. Osredotočili smo se na paket storitev Google Apps, ki predstavlja celovito rešitev za poslovanje podjetja.
Možnosti vpeljave Google Apps smo analizirali na primeru manjšega gradbenega in računovodskega podjetja. Found in: osebi Keywords: računalništvo, računalništvo v oblaku, spletne storitve, Google Apps, komunikacijska tehnologija, informacijski sistemi Published: 10.08.2018; Views: 3048; Downloads: 139 Fulltext (1,96 MB) |
20. Določanje normativnih količin materialov za pakiranje izdelkov v proizvodnem podjetjuNatalija Zoran, 2017 Abstract: Trg z vse večjo konkurenco zahteva od podjetij nenehne izboljšave za zviševanje kakovosti izdelkov, zniževanje stroškov in doseganje konkurenčnosti. Obravnavali smo proces določanja normativnih količin materialov za pakiranje končnih izdelkov v večjem proizvodnem podjetju, ki se ukvarja s proizvodnjo polizdelkov in pakiranjem končnih
izdelkov. V proces planiranje proizvodnje vključujemo celoten proces od trenutka vnosa prodajne napovedi oz. kupčevega naročila v informacijski sistem do trenutka lansiranja procesnega naloga za pokritje potreb. Na podlagi analiz izdelanih serij končnih izdelkov in porabljenih embalažnih materialov smo predlagali modele določanja normativnih materialov, ki upoštevajo velikost proizvodnega naloga in vrsto materiala. Found in: osebi Keywords: proizvodnja, planiranje, informacijski sistem, kosovnica, embalažni materiali Published: 24.08.2018; Views: 2894; Downloads: 134 Fulltext (1,28 MB) |