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Composition of the bacterial microbiota of donated human milk
No full textUvod: Istraživanja su pokazala utjecaj različitih obilježja na sastav bakterijske mikrobiote humanog mlijeka (HMM), no nisu provođena na uzorcima iz mješavina darovanog humanog mlijeka (DHM).
Cilj: Cilj istraživanja bio je identificirati sastav bakterijske mikrobiote DHM-a te istražiti postoje li obilježja koja mogu utjecati na zastupljenost rodova pojedinih bakterija.
Ispitanice i metode: Iz arhivskih uzoraka mješavina DHM-a izolirana je bakterijska deoksiribonukleinska kiselina. Sekvenciranjem nove generacije određena je zastupljenost operativnih taksonomskih jedinica bakterija i uspoređena s poznatim obilježjima darivateljica, njihove djece i darovanog mlijeka.
Rezultati: U istraživanje je uključeno 88 uzoraka DHM-a od 88 darivateljica. U zastupljenosti bakterijskih rodova između skupina uzoraka podijeljenih prema načinu poroda i izloženosti antibioticima nije bilo značajnih razlika. Razlike su nađene s obzirom na tjedne gestacije na porodu i tjedne laktacije, način hranjenja majčinim mlijekom, način izdajanja viška mlijeka, broj bakterija kultiviranih u mlijeku prije pasterizacije te duljinu trajanja i temperaturu pohrane.
Zaključak: Dojenje djece te kraća pohrana na -30 ⁰C u Banci ovim su se istraživanjem pokazali kao pozitivni prediktori za zastupljenost rodova Lactobacillus i Bifidobacetrium kao dio bakterijske HMM-e u uzorcima mlijeka.Introduction: Studies have shown the influence of different characteristics on the composition of the bacterial microbiota of human milk (HMM), they were not conducted on samples from pools of donated human milk (DHM).
Aim: The aim of the research was to identify the composition of the bacterial microbiota of DHM and to investigate whether there are characteristics that can influence the representation of certain bacterial genera.
Subjects and methods: Bacterial deoxyribonucleic acid was isolated from archival samples from pools of DHM. Using next generation sequencing, the representation of operational taxonomic units of bacteria was determined and compared with the known characteristics of donors, their children and DHM.
Results: 88 DHM samples were included in the research. There were no significant differences in the representation of bacterial genera between sample groups divided according to the mode of delivery and exposure to antibiotics. Differences were found regarding weeks of gestation at delivery and weeks of lactation, the method of feeding with breast milk, the method of expressing surplus milk, the number of bacterial colonies cultivated in milk before pasteurization, and the length of time and temperature of storage.
Conclusion: Breastfeeding of children and shorter storage at -30 ⁰C in the human milk bank have been shown as positive predictors for the presence of the genus Lactobacillus and Bifidobactrium as part of bacterial HMM in milk samples
Dario Fo's dramatic and acting opus
No full textDario Fo, talijanski glumac i dramatičar, poznat je po svojim dubokim i univerzalnim porukama koje prenosi kroz kazališne komade. Njegova djela istraživala su teme poput ljudske prirode, društvenih normi i moralnih dilema, što svakako doprinosi njihovoj univerzalnoj privlačnosti i relevantnosti za različite publike diljem svijeta neovisno o dobnim skupinama kao i kulturnim pozadinama. Disertacija pokazuje kako je Fo majstor u stvaranju likova i situacija koje lako prepoznajemo i s kojima se možemo poistovjetiti, što omogućuje publici dublji zaron u priču i razmišljanja o složenim temama poput emocija, životnih gubitka, identiteta i sukoba. Rad ispituje Foovu tehniku pisanja i inventivne pristupe kazalištu što je rezultiralo djelima koja su često kombinirala humor s dubokim emocijama i filozofskim promišljanjima. Ovaj doktorski rad, polazeći od različitih aspekata Foova opusa, na monografski način donosi nekoliko ključnih elemenata. Započinjući od povijesno-političkog konteksta afirmacije Darija Foa, rad istražuje njegove prve susrete s narativnom izvedbom, pri čemu osobitu pažnju pridaje onim povijesnim razdobljima koja su značajno utjecala na njegov izričaj i opus – osobito ono fašističko i njegovu poslijeratnu kritiku, kao i načine na koji su strukture fašizma ostavile trag na društvenoj kritici. Nadalje, rad istražuje dramaturgiju Darija Foa polazeći od profesionalnoga umjetničkog rada, osobnih životnih prilika pa sve do javnoga angažmana koji je u uskoj vezi s autorovim kazališnim radom. Doktorski rad sintetizira uvide u istraživanja o dramaturgiji Darija Foa u njegovoj opsežnoj i snažnoj kazališnoj kritici društva, osobito kroz forme humora i satire. Rad osobiti naglasak stavlja na istraživanje satire kao političke kritike društva, koja se čini dominantnom pojavom u Foovu opusu. Naposljetku, rad donosi nekoliko elemenata univerzalnosti kazališne kritike Darija Foa, a koja je jedan od najvažnijih razloga zbog kojeg je i postao dobitnik Nobelove nagrade. U ovakvom monografskom prikazu te analitičkim postupcima rad prikazuje važnost dramaturgije Darija Foa, utemeljene u povijesno-političkom kontekstu kritike talijanskog društva i političke ideologije fašizma, po svome karakteru univerzalne i primjenjive na različite forme političkih patologija koje se pojavljuju kao predmet kazališne kritike.Dario Fo, an Italian actor and playwright, is known for his deep and universal messages that he conveys through theater pieces. His works explored themes such as human nature, social norms and moral dilemmas, which certainly contributes to their universal appeal and relevance to diverse audiences around the world. Fo is a master at creating characters and situations that we can easily recognize and identify with, which allows the audience to dive deeper into the story and think about complex topics such as emotions, life's losses, identity and conflict. This doctoral thesis, starting from different aspects of Fo's opus, brings several key elements in a monographic manner. Starting from the historical-political context of Dario Fo's affirmation, this thesis investigates his first encounters with narrative performance, putting special attention to those historical periods that significantly influenced his expression and writing - especially the fascist period and its post-war criticism, and the ways in which structures of fascism left their mark on social criticism. Furthermore, the work explores the dramaturgy of Dario Fo, starting from professional artistic work, personal life circumstances and all the way to public engagement, which is closely related to the author's theatrical work. The doctoral thesis synthesizes insights from research into the dramaturgy of Dario Fo in his extensive and powerful theatrical criticism of society, especially through forms of humor and satire. The work places special emphasis on the research of satire as a political criticism of society, which seems to be a dominant phenomenon in Fo's oeuvre. Finally, the thesis brings several elements of the universality of Dario Fo's theater criticism, which is one of the most important reasons why he became a Nobel Prize winner. In this kind of monographic presentation and analytical procedures, the thesis shows the importance of Dario Fo's dramaturgy, based on the historical-political context of criticism of Italian society and the political ideology of fascism, universal in the world and applicable to various forms of political pathologies that appear as the subject of theater criticism
Samopoimanje učenika s ADHD poremećajem
No full textADHD (Attention Deficit/Hyperactivity Disorder) is a developmental disorder characterized by a persistent pattern of inattention and/or hyperactivity/impulsivity, which is a disruptive factor in the daily functioning of an individual (APA 2013).
Research in the field of attention deficit hyperactivity disorder in Croatia is scarce, and the majority of studies examine how the disorder is perceived by parents, educators, and others.
Since there is limited research in the available literature on how children with ADHD experience and perceive the disorder from their own perspective, the goal of this doctoral dissertation is to provide insight into the self-concept of students with ADHD, i.e., into the lived experience of everyday life related to education, relationships with peers, and family.
In order to gather qualitative responses to the research question, "How do students with ADHD perceive their own disorder in the context of education?" a purposeful (deliberate) sample was selected (Creswell, Miller, 2000). This approach allows the researcher to derive more accurate findings and deeper understanding of the subject matter. Taking into account the sensitive population, the choice of research model depended on a child-centered approach. As the phenomenological research model is an alternative to traditional methods and research, it was chosen as a more appropriate choice, as it is safe and adapted to the child's developmental characteristics. The sample consists of 13 regular elementary school students, from 1st to 8th grade, in the area of the city of Zagreb. The criteria for the selection of research participants was the diagnosis of ADHD disorder. Semi-structured in-depth interviews and observations were implemented as data collection methods, and a phenomenological approach was used to interpret the data through a qualitative thematic analysis. These themes are used to illustrate the experiences of students with ADHD through categorizes: (1) self-relationship; (2) relationships with peers; (3) relationships with family; and (4) relationships with adults/teachers.
The inclination with this type of exploratory phenomenology study was to look into how students with ADHD view and respond to various life circumstances.ADHD – Attention Deficit/Hyperactivity Disorder (deficit pažnje / hiperaktivni poremećaj) razvojni je poremećaj koji karakterizira trajni obrazac nepažnje i/ili hiperaktivnosti/impulzivnosti, a koji predstavlja ometajući faktor u svakodnevnom funkcioniranju pojedinca (APA 2013).
Istraživanja na području ADHD poremećaja u Hrvatskoj su rijetka, a većina ih u fokusu ima viđenje ADHD poremećaja od strane roditelja, nastavnika i vršnjaka. S obzirom na to da je u dostupnoj literaturi malo istraživanja koja se bave istraživanjem načina na koji sama djeca s ADHD poremećajem doživljavaju i percipiraju poremećaj iz vlastite perspektive, cilj je ove doktorske disertacije dati uvid u samopoimanje učenika s ADHD poremećajem, odnosno u doživljeno iskustvo svakodnevnog života vezanog uz školovanje, odnose s vršnjacima i s obitelji.
Polazeći od istraživačkog pitanja Kako učenici s ADHD poremećajem percipiraju vlastiti poremećaj u kontekstu obrazovanja?, za istraživanje je odabran svrhoviti (namjerni) uzorak (purposive / deliberate sampling) koji istraživaču omogućava prikupljanje kvalitativnih odgovora, što dovodi do boljih uvida i preciznijih rezultata istraživanja (Creswell, Miller 2000). Uzorak sačinjava 13 učenika redovne osnovne škole, od 1. do 8. razreda, na području grada Zagreba, a kriterij za izbor sudionika istraživanja bila je dijagnoza ADHD poremećaja.
Vodeći računa o osjetljivoj populaciji, izbor modela istraživanja ovisio je o pristupu usmjerenom na dijete. Kako je Fenomenološki model istraživanja alternativa tradicionalnim metodama i istraživanjima, odabran je kao najprimjereniji izbor, kao siguran i prilagođen djetetovim razvojnim osobinama. Kao tehnika dobivanja podataka koristili su se polustrukturirani dubinski intervju i opservacije, a podaci su obrađeni kvalitativnom tematskom analizom fenomenološkim pristupom. Iskustvo učenika s ADHD-om prikazano je temama: (1) Odnos prema sebi, (2) Odnos s vršnjacima, (3) Odnosi u obitelji, (4) Odnos s odraslima/učiteljima. Ovakvom eksploratornom fenomenološkom studijom tendiralo se istražiti načine na koje učenici s ADHD poremećajem percipiraju situacije u odgojno-obrazovnom procesu i kako se s njima nose
Intergroup attitudes in majority and minority families: the role of ethnic socialization, family cohesion and intergroup contact
No full textRoditelji mogu na različite načine prenositi međugrupne stavove svojoj djeci – izravno, poučavanjem, i neizravno, svojim ponašanjem te oblikovanjem okruženja u kojem djeca odrastaju. Cilj je ovog rada bio istražiti različite načine na koje roditelji mogu oblikovati međugrupne stavove svoje djece. Konkretno, ovim smo radom željeli procijeniti sličnost međugrupnih stavova djece i njihovih roditelja, te ispitati u kakvim je obiteljima i kakvim kontekstima ta sličnost izraženija. Također, provjerili smo uzajamne efekte međugrupnog kontakta djece i roditelja na njihove međugrupne stavove. U istraživanju smo koristili dio podataka prikupljenih u širem projektu, a uzorak se sastojao od 542 obitelji. Djeca su bila u dobi od 11 do 19 godina, odnosno u vrijeme provedbe istraživanja bili su adolescenti. Njihove majke imale su u prosjeku gotovo 43 godine, a očevi 46. Roditelji su u projektu sudjelovali u jednoj točki mjerenja, a njihova djeca u dvije, s razmakom od godine dana. U ovom se radu bavimo stavovima prema etničkim grupama, a uzorak uključuje, uz pripadnike etnički većinske grupe, i pripadnike četiri etnički manjinske grupe. To nam je omogućilo provjeru uloge grupnog statusa, ali i kontekstualnih faktora poput povijesti međuetničkih sukoba na međugrupne stavove roditelja i njihove djece. Rezultati su pokazali da su međugrupni stavovi roditelja i djece umjereno povezani. Sličnost međugrupnih stavova bila je veća u većinskim u odnosu na manjinske obitelji, kao i u postkonfliktnim u odnosu na nekonfliktne zajednice. Obiteljska kohezija i etnička socijalizacija nisu značajno moderirale odnos međugrupnih stavova roditelja i djece. Izravni međugrupni kontakt predviđao je pozitivnije međugrupne stavove i roditelja i djece, dok prošireni (stvarni i percipirani) kontakt uglavnom nije pokazao konzistentne efekte na stavove.Introduction: The development of intergroup attitudes is a complex process shaped by numerous internal and external factors, with parents being an important external factor in shaping their children's attitudes. Parents can have an impact on children's intergroup attitudes in various ways. They can have a direct role by explicitly teaching children what kind of attitudes they should have, and an indirect role by fostering an environment that encourages the formation of specific attitudes. In this dissertation we focus on interethnic attitudes among ethnic majority and minority families. Studies so far suggest that factors such as parental ethnic socialization, family cohesion, and parental intergroup contact can be important for the formation of intergroup attitudes in children. These processes seem to continue after childhood, possibly even more intensely, throughout adolescence. There is still a need for further research, especially to better understand the impact of group status and contextual factors, like the history of intergroup conflict, on the transmission of intergroup attitudes within families. Therefore, in this study we examined the similarity of intergroup attitudes between parents and their children among majority and minority families within post-conflict and non-conflict communities. In addition, we tested the role of ethnic socialization and family cohesion in the similarity of parent-child intergroup attitudes. Finally, in this study we explored the mutual effects of intergroup contact of parents and children, direct and extended, on their intergroup attitudes. Methodology: This dissertation is a part of the research project "Integration processes of majority and minority in ethnically mixed communities: The role of interethnic contact, perceived threat, and social norms" (IntegraNorm). The project included both minority and majority members from four multiethnic communities in Croatia. The research was carried out in collaboration with primary and secondary schools where education is conducted in Croatian, as well as in one of the four national minority languages (Serbian, Hungarian, Czech, and Italian). Accordingly, four majority-minority contexts were examined: Croatian-Serbian, CroatianHungarian, Croatian-Czech, and Croatian-Italian. The important distinction between these communities is the recency of open conflict between two ethnic groups. In three of the intergroup contexts (Croatian-Hungarian, Croatian-Czech, and Croatian-Italian), intergroup relations have remained mostly peaceful for decades, and we categorized them as non-conflict communities. In contrast, the Croatian-Serbian context is considered a post-conflict community, as it was affected by the 1991-1995 war. The IntegraNorm project utilized mixedmethods research design, including qualitative and quantitative approach. This dissertation draws on data from quantitative study, which involved adolescents and their parents. The quantitative study followed a cross-sectional and longitudinal design, with two waves of data collection. Adolescents participated in both waves, while their parents participated only in the first. Data from the first wave (involving both adolescents and their parents) was used to examine parent-child attitudinal similarity and to explore the role of ethnic socialization and family cohesion in shaping this similarity. To investigate the role of direct and extended intergroup contact, we used parental data from the first time point and longitudinal data from adolescents. The adolescent participants were drawn from the 6th and 7th grades of primary schools, as well as the 2nd and 3rd grades of secondary schools. In some schools, additional grades were included to ensure adequate sample sizes. The first wave of data collection took place between February and April 2017, followed by the second wave a year later. Adolescents completed their questionnaires during school hours, while parents filled out theirs at home. The initial sample consisted of 1,568 adolescents (55 % daughters, 45 % sons) and 2,000 parents (1,067 mothers, 933 fathers). To test our hypotheses, we needed to select a suitable subset from the broader project sample. The selection criteria were: (1) participation of all family members, (2) all family members sharing the same nationality, and (3) the family's nationality aligning with the context being studied. Based on these criteria, the final sample consisted of 542 ethnically homogeneous adolescent-mother-father families (67.16 % majority, 32.84 % minority families; 49.63 % from post-conflict, 50.37 % from non-conflict communities). Among others, adolescents and their parents completed three measures of intergroup attitudes: ingroup bias, social distance, and tendency to discriminate against the outgroup. While the measures were largely similar for both groups, some items were adjusted for adolescents and parents to better suit their experiences. Additionally, adolescents completed an extra measure related to intergroup attitudes – the propensity for prosocial behavior. For this study, we also used two family-related measures: ethnic socialization, assessed through parents, and family cohesion, measured across all family members. Finally, intergroup contact, direct and extended, was measured for all participants. The measures about intergroup relations were designed so that minority group members always expressed their relation towards the majority, while majority group members indicated their relation towards the minority group that was predominant in their community. To test our main hypotheses, we used structural equation modeling, including longitudinal analysis and analyses designed in the framework of dyadic research.
Results: Results indicated a positive correlation between the intergroup attitudes of adolescents and their parents, suggesting that children whose parents held more positive intergroup attitudes also tended to have more positive attitudes themselves. This similarity seems to be higher in majority families compared to minority families, as well as in post-conflict communities compared to non-conflict ones. However, neither family cohesion nor ethnic socialization significantly moderated the relationship between parents' and children's intergroup attitudes. The absence of significant findings regarding the moderating effects of family cohesion may be due to the limited variability in these measures within the sample. Most participants reported high levels of family cohesion, potentially reducing the ability to detect its moderating role. Similarly, the measures of ethnic socialization may not have captured the full spectrum of socialization practices relevant to intergroup attitudes in studied contexts. Direct intergroup contact, measured as the number of friends from the outgroup, predicted more favorable intergroup attitudes in both adolescents and parents. The effects of direct contact did not significantly differ based on group status (majority vs. minority) but did exhibit some differences depending on the intergroup context, although not as expected. However, actual extended contact, e.g. the effects of parents' intergroup friendships on their children's attitudes and vice versa, were not consistent across different analyses. When analyzing the data from the two time points, we found a significant correlation between changes in perceived extended contact and intergroup attitudes among adolescents. Those who experienced a more substantial decrease in their perception of extended contact had less positive intergroup attitudes over time. However, it is important to note that these conclusions may be flawed due to the relatively small sample size, especially in the subgroups, the possibility of small underlying effects, and the complexity of the studied models.
Conclusion: In conclusion, this dissertation contributes to the expanding collection of research emphasizing the significant role parents play in shaping their children's intergroup attitudes. Our findings provide support for the importance of group status and social context in parentchild attitudinal similarity. While parents do have a role in their children's intergroup attitudes, the underlying mechanisms seem complex and require further exploration, particularly in relation to the differences across various status groups and social contexts
Algoritmi i konvergencija metoda Jacobijeva tipa
No full textThe Jacobi eigenvalue algorithm is a well-known iterative method used for solving the eigenvalue problem of symmetric matrices. The process is based on matrix diagonalization. In this thesis we study several modifications of the Jacobi method. We work on both matrix and tensor numerical problems. First, we review and generalize the Eberlein method, which is a Jacobi-type method for diagonalization of an arbitrary matrix. We prove the global convergence of the Eberlein method under a broad class of generalized serial pivot strategies with permutations. Moreover, we discuss the cases of unique and multiple eigenvalues. Next, we consider block-partitioned matrices and introduce a block version of the Eberlein method. We give a convergence proof for the block Eberlein algorithm under the already mentioned class of generalized serial pivot strategies. Lastly, we study the methods for approximate tensor diagonalization. We propose an iterative Jacobi-type trace maximization algorithm for solving this problem on general tensors, as well as the structure-preserving variant for the symmetric tensors. We prove the global convergence for both of our algorithms. All theoretical work is accompanied by numerous numerical examples.Jacobijev algoritam je poznata iterativna metoda za rješavanje problema svojstvenih vrijednosti za simetrične matrice. Postupak se temelji na dijagonalizaciji matrice. U ovoj se disertaciji bavimo modifikacijama Jacobijeve metode koje koristimo za rješavanje numeričkih problema za matrice i tenzore. U prvom dijelu rada proučavat ćemo Eberleininu metodu Jacobijevog tipa za dijagonalizaciju opće matrice. Poopćit ćemo Eberleininu metodu i dati dokaz globalne konvergencije za široku klasu tzv. generaliziranih serijalnih pivotnih strategija s permutacijama. Analizirat ćemo slučaj jednostrukih i višestrukih svojstvenih vrijednosti. Nadalje, promatrat ćemo matrice s blok-particijom te uvesti blok verziju Eberleinine metode. Dat ćemo dokaz konvergencije blok Eberleininog algoritma za već spomenutu klasu generaliziranih serijalnih pivotnih strategija. Naposljetku, promatrat ćemo problem približne dijagonalizacije tenzora. Predstavit ćemo iterativni algoritam Jacobijevog tipa temeljen na maksimizaciji traga tenzora. Konstruirat ćemo algoritam za opće tenzore te njegovu varijantu za simetrične tenzore u kojoj je očuvana polazna simetrična struktura. Za oba algoritma dokazat ćemo globalnu konvergenciju. Svi teorijski rezultati će biti popraćeni brojnim numeričkim primjerima. Disertacija je podijeljena u četiri poglavlja. U prvom poglavlju dan je osvrt na rezultate iz literature. Opisan je realni i kompleksni Jacobijev algoritam za rješavanje problema svojstvenih vrijednosti i izvedene su formule za računanje kutova transformacije. Opisano je nekoliko klasa pivotnih strategija. Poglavlje se nastavlja teorijom o Jacobijevim anihilatorima i operatorima koji se koriste u brojnim rezultatima o konvergenciji za standardnu Jacobijevu metodu i za druge metode Jacobijeva tipa. Koristit ćemo tu teoriju za dokaz konvergencije Eberleinine metode po elementima, ali i njene blok varijante. Prvo poglavlje završava osvrtom na teoriju o konvergenciji Jacobijeva algoritma. Drugo poglavlje temelji se na članku [10] od Begović Kovač i Perković objavljenom 2024. godine. Prvo je dan pregled postojećih rezultata o konvergenciji Eberleinine metode, za realni i kompleksni slučaj. Glavni dio poglavlja je proširenje globalne konvergencije metode na široku klasu generaliziranih serijalnih pivotnih strategija. Pokaže se da, za proizvoljnu početnu matricu A, Eberleinina metoda konvergira uz bilo koju strategiju iz navedene klase. Niz matrica , koji se dobije nakon svake iteracije, konvergira prema normalnoj matrici. Niz hermitskih dijelova dobivenih matrica, , konvergira prema dijagonalnoj matrici takvoj da su na dijagonali realni dijelovi svojstvenih vrijednosti od . Ako sve svojstvene vrijednosti od imaju različite realne dijelove, niz konvergira prema dijagonalnoj matrici sa svojstvenim vrijednostima od na dijagonali. Inače, svojstvene vrijednosti s jednakim realnim dijelovima mogu dovesti do ne-nul van-dijagonalnih elemenata u dobivenoj matrici. Kroz numeričke primjere testirana je metoda na realnim i kompleksnim matricama, za početne matrice koje su unitarno dijagonalizabilne i za one koje to nisu. Promatrana je promjena u matričnoj van-dijagonalnoj normi, tj., udaljenosti od dijagonalne matrice. Nadalje, pokazana je blok struktura koja se pojavljuje ako početna matrica ima višestruke svojstvene vrijednosti. Naposljetku, pokazano je kako numerički riješiti problem kod ponavljajućih svojstvenih vrijednosti. Treće poglavlje sadrži prijedlog novog blok Eberleininog algoritma. Dan je kratki uvod u blok matrice i blok algoritme. Opisana je blok verzija Eberleinine metode u kojoj su matrice podijeljene u blokove. Zatim, predložen je način za računanje transformacija i , te dan dokaz konvergencije algoritma uz generalizirane serijalne pivotne strategije. Rezultati konvergencije su u skladu s onima za Eberleininu metodu po elementima. Numeričkim testovima pokazano je kako blok algoritam radi za različite veličine blokova i za ponavljajuće realne dijelove svojstvenih vrijednosti. Četvrto i posljednje poglavlje orijentirano je na približnu dijagonalizaciju tenzora. Temelji se na članku [11] od Begović Kovač i Perković objavljenom 2024. godine. Ovdje je detaljno objašnjena terminologija i pojmovi vezani uz tenzore koji se koriste u tenzorskom računu. Prvo je dan osvrt na postojeće algoritme za dijagonalizaciju tenzora. Zatim je iznesen prijedlog algoritma koji se temelji na maksimizaciji traga tenzora, kao u [65]. Algoritam koristi metodu alternirajućih najmanjih kvadrata (ALS). Naime, jedna iteracija algoritma na tenzoru reda sastojat će se od mikroiteracija. Pokazana je globalna konvergencija našeg algoritma za opće tenzore. Preciznije, pokazano je da je svako gomilište dobiveno našim algoritmom stacionarna točka funkcije koju maksimiziramo. Ovaj rezultat istog je tipa kao rezultati konvergencije algoritama za dijagonalizaciju tenzora koji se baziraju na maksimizaciji Frobeniusove norme dijagonale tenzora. Konvergencija vrijedi za sve cikličke strategije uz dodatni uvjet na pivotni par , zvan Łojasiewitzeva nejednakost gradijenta. Nadalje, naš algoritam maksimizacije traga prilagođen je kako bi se očuvala struktura simetričnih tenzora. U tom slučaju, svih d rotacija koje djeluju u jednoj iteraciji moraju biti iste. Prema tome, ovo više nije ALS algoritam jer se trag maksimizira po svim modovima istovremeno. Ipak, dokaz konvergencije će ići uz bok dokazu za algoritam koji ne čuva strukturu. Numerički primjeri uključuju testove oba algoritma na tenzorima različitih redova, dijagonalizabilnih tenzora i onih koji to nisu. Promatrano je povećanje traga tenzora i smanjenje van-dijagonalne norme tenzora, te su dane usporedbe za različite cikličke pivotne strategije
Dinamika na hiperprostoru jednodimenzionalnih kontinuuma
No full textWhenever we are given a selfmap of a compact metric space , we can associate with it the induced mappings and on the hyperspace of compact subsets of and the hyperspace of continua in , respectively, both defined in a natural way. This thesis concentrates on the relationship between the certain properties of selfmaps of some one-dimensional continua and of the induced mappings on their respective hyperspaces of subcontinua. Specifically, first we present the equality of the topological entropies of the arbitrary graph map and its induced mapping on the hyperspace of subgraphs. In order to do so, we characterize the set of subgraphs which are recurrent under the induced mapping. Further, we describe the structure of -limit sets of the induced mapping on the hyperspace of continua for an arbitrary graph map. Strictly speaking, we prove that any subgraph is either asymptotically periodic, wandering or almost all of its iterates lie in a subsystem which is an almost 1-1 extension of irrational rotation, thus generalizing the earlier results obtained in the cases of compact intervals and topological trees. In the last chapter of the thesis, for every tree map , we establish the relation between the periods of the subtrees which are the periodic points of and the periods of periodic points of contained in those subtrees. We close the thesis by showing how the latter result can be used in order to prove some properties of the induced system on the hyperspace of continua. For any tree map , we provide complete description of the Birkhoff center of and prove its almost equicontinuity.Kad god je zadano preslikavanje na kompaktnom metričkom prostoru , možemo mu pridružiti inducirana preslikavanja i na hiperprostoru kompaktnih podskupova od i hiperprostoru kontinuuma u , redom, oba definirana na prirodan način. Kroz disertaciju smo usredotočeni na istraživanje odnosa između određenih svojstava preslikavanja na nekim jednodimenzionalnim kontinuumima i njihovih induciranih preslikavanja na pripadnim hiperprostorima potkontinuuma. Preciznije, prvo se bavimo uspostavljanjem jednakosti topoloških entropija proizvoljnih preslikavanja na topološkim grafovima i njihovih induciranih preslikavanja na hiperprostorima podgrafova. Kako bismo to postigli, karakteriziramo skup podgrafova koji su rekurentni s obzirom na inducirano preslikavanje. Nadalje, opisujemo strukutru -graničnih skupova induciranog preslikavanja na hiperprostoru kontinuuma za proizvoljno preslikavanje topološkoga grafa. Strogo govoreći, pokazujemo da je svaki podgraf asimptotski periodičan, lutajuć ili su gotovo sve njegove iteracije sadržane u podstustavu koji je gotovo 1-1 proširenje iracionalne rotacije. Ovaj rezultat poopćava ranije dobivene rezultate u slučajevima kompaktnog intervala i topološkog stabla kao baznih prostora. U posljednjem poglavlju disertacije za svako preslikavanje na topološkom stablu uspostavljamo odnos između perioda podstabala koja su periodičke točke od i perioda periodickih točaka of , sadržanih u tim podstablima. Za kraj pokazujemo kako upravo spomenuti rezultat može biti koristan pri dokazivanju određenih svojstava induciranog sustava na hiperprostoru kontinuuma. Naime, za proizvoljno preslikavanje na topološkom stablu dajemo potpun opis Birkhoffovog centra od i dokazujemo njegovu gotovo ekvikontinuiranost
Relationship between the degree of digitalization of accounting processes and the quality of work of the accounting profession
No full textDigitalizacija poslovanja poduzeća i njihovih računovodstvenih procesa donosi promjene u načinu na koji poduzeća djeluju kao i u načinu na koji zaposleni radnici izvršavaju svoje radne zadatke. Implementacija tehnoloških inovacija za cilj bi trebala imati unaprjeđenje djelovanja pojedinaca, poduzeća kao i cjelokupnog društva. Dosadašnja istraživanja ukazuju na primjetne promjene u radu računovodstvenih profesionalaca pod utjecajem digitalne transformacije poduzeća i njihovih računovodstvenih odjela, a koje je moguće dovesti u vezu s kvalitetom rada samih računovodstvenih radnika. Kako bi se ispitalo koje su ključne odrednice kvalitete rada računovodstvene profesije provedeno je predistraživanje te su podaci o potvrđenim ključnim odrednicama kvalitete rada računovodstvene profesije korišteni u drugom dijelu istraživanja. Prvom hipotezom testirana je povezanost digitalizacije računovodstvenih procesa poduzeća s kvalitetom rada računovodstvene profesije pri čemu su ujedno identificirani i ključni tehnološki postupci digitalizacije računovodstvenih procesa u poduzećima u Republici Hrvatskoj. Hipoteza je testirana zasebno za svaku odrednicu kvalitete rada računovodstvene profesije te je potvrđena za odrednicu kvalitete rada poznavanje, praćenje i usvojenost zakonskih odredbi i regulative iz područja računovodstva i ostalih povezanih grana ekonomije. Drugom hipotezom testirana je i uspoređena razina digitalizacije računovodstvenih procesa eksterno i interno orijentiranoga računovodstva. Hipoteza je potvrđena odnosno pokazalo se kako je razina digitalizacije računovodstvenih procesa eksterno orijentiranoga računovodstva viša od razine digitalizacije računovodstvenih procesa interno orijentiranoga računovodstva. Postoji li značajna razlika u stupnju digitalizacije računovodstvenih procesa između mikro, malih, srednjih i velikih poduzeća testirano je trećom hipotezom te je hipoteza potvrđena za varijablu vrijednost uloženih financijskih sredstava u digitalizaciju računovodstvenih procesa. Posljednjom je hipotezom utvrđeno da gospodarska razvijenost regije poduzeća nema utjecaja na stupanj digitalizacije računovodstvenih procesa. Rezultati provedenih istraživanja mogu biti od koristi poduzećima, regulatorima, računovodstvenim strukovnim udruženjima kao i profesionalnim računovođama te su ovime zadovoljeni postavljeni znanstveni i aplikativni ciljevi doktorskog rada.Digitalization of business operations of companies and their accounting processes has brought changes in the way companies operate as well as in the way employees perform their work tasks. The goal of implementing technological innovations should be to improve the performance of individuals, companies, and society as a whole. Previous research indicates notable changes in the work of accounting professionals under the influence of the digital transformation of companies and their accounting departments, which can be linked to the quality of work of the accountants themselves. Technological innovations in the field of accounting in the last few decades have fundamentally changed the way accountants work. Data recording in accounting has been significantly accelerated, business books and financial reports have become more accurate and thus more reliable, accountants have been freed from repetitive tasks and can focus on more creative and complex tasks. As a result, the role of accountants in the company is also changing - from administrative workers who record data they are turning into advisors to the management, with information about the success and safety of a company's operations. In order to examine what are the key determinants of the quality of work of the accounting profession, a preliminary study was conducted using the Delphi method. Out of ten offered determinants of the quality of work, five key determinants were identified through the preliminary research:
• knowledge, monitoring and comprehension of legal provisions and regulations in the field of accounting and other related branches of the economy
• accuracy and reliability
• meeting deadlines and timeliness in the execution of work tasks
• level of support to the management
• digital skills.
The data on the identified key determinants of the quality of work of the accounting profession determined by the preliminary research were used in the second part of the research.
Empirical research on the connection between the digitalization of accounting processes and the quality of work of the accounting profession followed the preliminary research and was carried out using a survey questionnaire. The data collected by the questionnaire was statistically analyzed, with descriptive analysis and multiple regression analysis used as the main statistical methods. Digitalization of accounting processes, measured by the number of implemented digitalized technological procedures, is the first independent variable, while the second independent variable is the value of financial resources invested in the development of digitalization of accounting processes. The dependent variable is the quality of work of the accounting profession. The connection between the digitalization of a company's accounting processes and the quality of work of the accounting profession was tested by the first hypothesis of the doctoral thesis. At the same time, the key technological procedures of the digitalization of accounting processes in companies in the Republic of Croatia are also identified here. The hypothesis was tested separately for each determinant of the quality of work that was identified as a key determinant during the preliminary research. A higher degree of digitalization of a company's accounting processes is positively related to some, but not all, determinants of the quality of work of the accounting profession. The hypothesis was confirmed for the knowledge, monitoring and comprehension of legal provisions and regulations in the field of accounting and other related branches of the economy determinant. There is a connection between the number of implemented technological procedures of digitalized accounting processes and the quality, knowledge, monitoring and comprehension of legal provisions and regulations in the field of accounting and other related branches of the economy determinant, measured by the variables ‘number of hours per week within the working hours of an accountant spent on monitoring the provisions and regulations in accounting and other related branches of economy’ and the ‘use of a software solution’, which implies warnings about current changes in legal provisions and regulations in the field of accounting and other related branches of the economy. The first hypothesis is partially accepted, and the connection is statistically significant for the knowledge, monitoring and comprehension of legal provisions and regulations in the field of accounting and other related branches of the economy determinant. The hypothesis was not confirmed for the other determinants of the quality of work of the accounting profession. The second hypothesis tested and compared the level of digitalization of accounting processes of externally and internally oriented accounting, and the hypothesis was accepted, that is, it was confirmed that the level of digitalization of accounting processes of externally oriented accounting is higher than that of internally oriented accounting. The testing was carried out by using the Wilcoxon test of differences, whereby a statistically significant difference was established in the share of implemented technological procedures for the digitalization of accounting processes in externally and internally oriented accounting. On average, companies have implemented 44% of the technological procedures for digitalizing the accounting processes of externally oriented accounting and 31% of the technological procedures for digitalizing the accounting processes of internally oriented accounting. Externally oriented technological procedures of digitalization of accounting processes are those whose application is aimed at reporting to external users. Unlike the external, the implemented internal technological procedures of digitalization of accounting processes are those whose application is aimed at reporting to internal users. Internally oriented accounting is mostly based on estimates, current, and future events. Externally oriented accounting is based on past events and is primarily oriented towards reporting to external users on the achieved business results. The third hypothesis tested whether there is a significant difference in the degree of digitalization of accounting processes between micro, small, medium, and large enterprises. This hypothesis was partially confirmed. It was confirmed for the ‘value of financial resources invested in the digitalization of accounting processes’ variable. This implies that larger companies invest more financial resources in the digitalization of accounting processes, and as the size of the company decreases, the value of the financial resources invested in the digitalization of accounting processes decreases as well. The hypothesis was not confirmed for the digitalization level variable measured by the number of implemented technological procedures for the digitalization of accounting processes, and in this aspect, there is no statistically significant difference among companies of different sizes. The last hypothesis has established that the economic development of a company's region has no effect on the degree of digitalization of accounting processes. When testing the fourth hypothesis, the independent variable was the geographical location with four categories, each category belonging to one region of the Republic of Croatia, while the dependent variable was the degree of digitalization of accounting processes. The fourth hypothesis of the research problem was tested by using the Kruskal-Wallis test of differences. Based on the results of the Kruskal-Wallis test of differences between regions, it was determined that there is no statistically significant difference in the number of implemented technological procedures for the digitalization of accounting processes. This implies that companies in all regions have an equal number of implemented technological procedures for the digitalization of accounting processes. Based on the same test, it was also determined that there is no statistically significant difference in the values of financial resources invested in the digitalization of accounting processes, i.e. companies in all regions equally invest financial resources in the digitalization of accounting processes.
The process of digitalization of accounting processes is a continuous sequence of implementation of technological innovations in accounting systems that can be observed in the past few decades, and which will certainly continue to be present within accounting systems in the future as well. Partial digitalization of accounting processes is primarily the result of the still extremely high costs of technological implementation. Digitalization of accounting processes is still not fully established in many companies and requires the efforts of the accounting profession in the implementation of digital transformation. Although the results of digitalization are still not visible in terms of connection of various platforms and systems, which would make the work of accounting professionals easier and simpler, digitalization has certainly changed the structure of the work tasks of accountants and improved the quality of their work. The collected and analyzed data on the degree of digitalization of accounting processes and the quality of work of the accounting profession can be useful to companies, regulators, professional accounting associations as well as to professional accountants. The conducted research has fulfilled the scientific and practical goals of the doctoral thesis
Assotiations of nutritional and periodontal status with the intima-media thickness of carotid arteries in kidney transplant recipients
No full textUVOD: Cilj ovog istraživanja bio je procijeniti IMT kao surogatnog markera ateroskleroze i analizirati moguće čimbenike rizika za povećanje vrijednosti IMT-a kod bolesnika s transplantiranim bubregom te analizirati njegovu povezanost s nutritivnim i parodontološkim statusom. Ovo istraživanje je analiziralo povezanost adropina s parametrima sastava tijela u bolesnika s TB-om, posebno naglašavajući razlike između spolova. MATERIJALI I METODE: U ovo je istraživanje uključeno 93 bolesnika s TB-om. Prikupljeni su podaci o kliničkim i laboratorijskim parametrima, sastavu tijela, antropometriji, mjerenjima krajnjih produkata glikacije, krvnom tlaku i krutosti arterija. Svi sudionici podvrgnuti su ultrazvučnom pregledu IMT-a i procjeni parodontološkog statusa. Razine adropina u serumu određene su s pomoću komercijalnog ELISA testnog kompleta. REZULTATI: TB s vrijednosti IMT ≥ 0,9 bili su značajno stariji, imali su nižu razinu ukupnog kolesterola, masnog tkiva i manji broj zuba. Također su imali značajno više vrijednosti PWV-a, RI-a i EDV-a. Potvrdili smo pozitivnu korelaciju između vrijednosti IMT-a i trajanja dijalize, dobi, parametara krutosti krvnih žila, AGE-a, RI-a i CAL-a. Regresijski model je pokazao da je IMT u TB-u povezan s većom krutošću krvnih žila, pothranjenosti i manjim brojem zuba. Bolesnici s TB i IMT ≥ 0.9 mm imali su manji broj zuba i veću vrijednost CAL-a. Ti parodontološki parametri su se dokazali kao najvažniji prediktori IMT-a u TB. Analiza je obuhvatila podskupinu bolesnika od 59 TB-a (28 žena u postmenopauzi i 31 muškarca), koje su dodatno kategorizirane prema vrijednostima adropina u odnosu na prosječnu vrijednost svake skupine. Univarijatna regresijska analiza pokazala je negativnu povezanost razina adropina s većinom antropometrijskih i parametara sastava tijela u muških TB-a. Suprotno tome, razina adropina u serumu bila je negativno povezana samo s faznim kutem u ženskih TB-ova. Multivarijatna regresija analiza pokazala je da su u ženskoj skupini TB-a skeletna mišićna masa i fazni kut bili jedini negativni prediktori, dok su u muškaraca negativni prediktori bili ITM i udio tjelesne vode. ZAKLJUČAK: Rezultati našeg istraživanja sugeriraju da su nutritivni i parodontološki status povezani s većom vrijednosti IMT-a kod TB-a. Nalazi sugeriraju da adropin može imati različit utjecaj na metaboličku homeostazu u TB-ova s obzirom na spol i može se smatrati negativnim prediktorom sastava tijela u ovoj skupini bolesnika. Glavna snaga ovog našeg istraživanja bolesnika s TB-om je u tome što je ovo prva studija analize povezanosti parodontoloških, nutritivnih parametara i medijatora upale poput adropina sa zadebljanjem intima-medije kao zamjenskog markera subkliničke ateroskleroze i KV rizika.INTRODUCTION: This study aimed to evaluate intima-media thickness (IMT) as a surrogate marker for atherosclerosis and to analyze potential risk factors associated with increased IMT values in kidney transplant patients as well as to analyze its connection with nutritional and parodontal status. This study analyzed the relationship between adropin levels and body composition parameters in kidney transplant patients, with a particular focus on gender differences. MATHERIALS AND METHODS: This study included 93 kidney transplant patients. Clinical and laboratory parameters, body composition, anthropometrics, advanced glycation end products (AGEs), blood pressure, and arterial stiffness measurements were collected. All participants underwent ultrasound examination of IMT and periodontal assessment. Adropin levels in serum determined with comercial ELISA test set. RESULTS: Patients with IMT values ≥ 0.9 mm were significantly older, had lower levels of total cholesterol, less adipose tissue, and fewer teeth. They also showed significantly higher values for pulse wave velocity (PWV), resistive index (RI), and end-diastolic velocity (EDV). We confirmed a positive correlation between IMT values and dialysis duration, age, vascular stiffness parameters, AGE, RI, and clinical attachment loss (CAL). Regression modeling indicated that IMT in kidney transplant recipients was associated with higher vascular stiffness, malnutrition, and a lower number of teeth. Kidney transplant recipients with IMT ≥ 0.9 mm had less number of teeth i higher value of CAL. These parodontal paramete have proven to be the most important predictors of IMT in KTR. The analysis included a subset of 59 transplant patients (28 postmenopausal women and 31 men), further categorized based on adropin values relative to the average within each group. Univariate regression analysis revealed a negative association between adropin levels and most anthropometric and body composition parameters in male transplant patients. In contrast, serum adropin levels were negatively associated only with phase angle in female patients. Multivariate regression analysis showed that skeletal muscle mass and phase angle were the only negative predictors in the female group, while in men, body mass index (BMI) and body water percentage were negative predictors. CONCLUSION: Our findings suggest that nutritional and periodontal status are associated with higher IMT values in kidney transplant patients. These findings suggest that adropin may have a sex-specific impact on metabolic homeostasis in kidney transplant patients and may be considered a negative predictor of body composition within this patient group. The primary strength of this study on kidney transplant recipients lies in being the first to analyze the association between periodontal and nutritional parameters and inflammatory mediators like adropin with intima-media thickness as a marker of subclinical atherosclerosis and CV risk
PHOTOCATALYTIC DECOMPOSSITION OF METHANE AS A TECHNOLOGY FOR REDUCING EMISSIONS FROM LOWMETHANE MUNICIPAL WASTE LANDFILLS
No full textOdlagališta otpada predstavljaju ekološke, ekonomske i društvene izazove, prvenstveno zbog
onečišćenja nastalog od organskog otpada koji se raspada u samom odlagalištu. Razgradnjom
organskog otpada nastaje metan (CH4), staklenički plin koji doprinosi klimatskim promjenama.
Metan (CH4) se obično zbrinjava spaljivanjem čime ga se pretvara u ugljični dioksid (CO2) i
vodenu paru (H2O). Međutim, kada su razine metana ispod 20 %, spaljivanje na baklji postaje
neisplativo, što dovodi do njegovog izravnog ispuštanja u atmosferu.
U predmetnom istraživanju stoga je istražen potencijal fotokatalitičke oksidacije s ciljem samog
razvitka prikladne tehnologije za zaštitu zraka iznad odlagališta otpada. Ovaj proces koristi
Sunčevo zračenje i fotokatalizator, a pokazao se učinkovitim i isplativim za razgradnju
onečišćivala poput metana (CH₄) u odlagališnom plinu. Uz navedeno, razvijen je i matematički
model za računalnu simulaciju i dizajn budućih sustava za smanjenje emisija odlagališnih
plinova na samom izvoru.
Ispitivanje fotokatalitičke razgradnje na uzorku stvarnog metana (CH₄) s odlagališta neopasnog
otpada Totovec pokazalo je smanjenje metana (CH₄) za približno 20 %. Iako je smanjenje bilo
nešto niže od očekivanog, rezultati su potvrdili učinkovitost fotokatalitičke oksidacije, čak kada
je koncentracija metana nešto niža (< 10 %).
Matematički model otkrio je ključne čimbenike koji utječu na razgradnju metana (CH₄) u
prstenastom reaktoru, osobito važnost duljine cijevi. Iako je model bio učinkovit, upotreba alata
računalne dinamike fluida za simulaciju pokazala se izazovnom zbog potrebe za opsežnom
prilagodbom i stručnošću za ovu specifičnu primjenu.Landfills are places intended for the disposal of solid waste and, as such, carry numerous
ecological, economic, and social problems. The decomposition of organic waste at landfills
produces methane (CH4), a greenhouse gas that is 25 times more potent than carbon dioxide
(CO2) in terms of heat retention, according to the Intergovernmental Panel on Climate Change
(IPCC). Accordingly, landfills represent one of the largest sources of methane (CH4) resulting
from human activity.
To reduce methane (CH4) emissions at landfills, landfill gas collection systems are often
installed to "capture" methane (CH4) and other gases emitted during the decomposition of
organic waste and transport them to a centralized facility for disposal. The most common
method of methane (CH4) disposal at landfills is flaring, which converts methane into carbon
dioxide (CO2) and water vapor (H2O). This practice is typical when the methane (CH4) content
in the landfill gas is at least 20%. When concentrations are lower, flaring becomes economically
unfeasible, leading to the release of methane into the atmosphere.
For this reason, the potential of photocatalytic oxidation was explored in this study on a real
landfill gas sample with lower methane (CH4) content. The goal of the study was to develop an
effective air protection technology for use at the source of landfill gas emissions. Photocatalytic
oxidation is a process that uses light-activated photocatalysts to create redox reactions that
degrade pollutants such as volatile organic compounds (VOCs) into harmless substances like
water and carbon dioxide (CO2).
The expected scientific contribution of this research is to confirm the effectiveness of solar
photocatalysis and demonstrate that it is a suitable technology for air protection above landfills,
which could potentially be used at the source of landfill gas emissions. Additionally, the
development of a mathematical model for the photocatalytic degradation of air pollutants will
provide the foundation for scaling up the process and applying it in real systems.
For the purpose of the research, the following four hypotheses were proposed: (1) Methane
(CH4), whose content in landfill gas composition is variable, can oxidize to carbon dioxide
(CO2) with the available amount of oxygen at the outlet from the landfill body; (2) Hydrogen
sulphide (H₂S), a component of landfill gases, is separated by the adsorption process from the
gas stream and remains on the photocatalytic material; (3) Suitable photocatalytic materials
based on titanium dioxide (TiO2) can be used for extended periods and regenerated if necessary
IX
before reuse; (4) An annular-type photocatalytic reactor represents a model system for the
simple upgrade of gas wells within the landfill body.
The first phase of research included the selection of photocatalytic material based on previous
research on commercial photocatalysts. Research has shown that titanium dioxide (TiO2) has
the most effective photoactivity, the highest stability and the lowest costs, which is why it was
chosen as the photocatalyst for conducting research. In the research itself, the photocatalyst was
applied to a mesh of glass fibres.
The next step in the research was the assembly of a laboratory photocatalytic reactor.
Photocatalytic reactors for air treatment require appropriate design with the aim of achieving
high quantum yields for long operating times with minimal costs. In order to achieve the above,
it is necessary to choose the appropriate configuration of the reactor and the source of UV
radiation in addition to the photocatalyst. In the test, an annular type of reactor was used, which
consists of two glass, concentric cylinders, between which the reaction mixture flows. The light
source (UV lamp) is placed in the inner cylinder, parallel to the tube. To simulate solar
radiation, Narva BIO vital® LT T5 24W / 958, UV lamp with the length of 549 mm was used.
The lamp in question emits radiation with a characteristic part of the UV-A and UV-B spectrum
(λ > 315 – 400 nm).
As a final step, the photocatalytic reactor was modelled using Computational Fluid Dynamics
(CFD). The computer program COMSOL Multiphysics was used for data visualization. In
addition to visualization, the mentioned computer program also enabled the computer
simulation of methane (CH4) decomposition in the test reactor using the estimated kinetic
parameters. Computer simulations were performed for different cases in order to be able to
compare the results obtained by the research with those obtained in the computer simulation.
The purpose of the above was to check the accuracy of the computer simulation, which will
ultimately enable further optimization of the test system and the adaptation of future potential
air protection systems above the waste disposal site.
Regarding the results themselves, based on which the proposed hypotheses were confirmed, the
results of the photocatalytic oxidation of methane (CH4) on a real gas sample from the
"Totovec" non-hazardous waste landfill showed an average reduction in methane (CH4)
concentration of 19.91 % across three measurements, specifically 21.59 % in the first
measurement, 18.15 % in the second, and 20.00 % in the third measurement. The
aforementioned confirmed the effectiveness of photocatalytic oxidation as methane (CH4) was
X
oxidized to carbon monoxide (CO) and carbon dioxide (CO2). This was confirmed by observing
the decomposition products, evidenced by a 30 % increase in carbon monoxide (CO) levels, as
CO concentrations rose from 2 to 3 ppm in the first and second tests and from 3 ppm to 4 ppm
in the third test.
Regarding the second hypothesis, the presence of hydrogen sulphide (H2S) in the landfill gas
samples was low (< 100 ppm) due to the prior separation of food waste at the source (the
landfill), and no significant difference in methane (CH4) degradation efficiency was observed
between samples with and without hydrogen sulphide (H2S) during the testing.
The third hypothesis was confirmed by using a fiberglass mesh in the research. The fiberglass
mesh served as a carrier for the photocatalyst, titanium dioxide (TiO2), and enabled efficient
photocatalytic oxidation due to its large surface area and porous structure, as supported by the
results of the photocatalytic oxidation during the study. This mesh had previously proven to be
a very good solution, as it could be regenerated after use through thermal treatment, thereby
extending its usage time. Thermal regeneration of the fiberglass mesh was effective due to the
high thermal stability of titanium dioxide (TiO2), allowing the removal of organic pollutants
through thermal oxidation. This kept the surface clean and ready for the further adsorption of
pollutants for additional photocatalytic degradation.
Concerning the fourth hypothesis, the annular-type photocatalytic reactor represents a model
system for the simple upgrade of gas wells at landfills due to its efficient design. The ring shape
allows for a larger surface area for the photocatalyst, promoting effective interaction between
the landfill gases and the used catalyst, as demonstrated in the model simulation created in the
COMSOL Multiphysics software. This design, being of a ring type, facilitates integration into
existing landfill gas collection systems, which are cylindrical in shape and thus require minimal
modifications to the gas wells
Optimal allocation and sizing of distributed generations and capacitor banks at multiple voltage levels of a distribution network : doctoral thesis
No full textOvaj doktorski rad istražuje optimalan razmještaj distribuiranih izvora i kondenzatorskih baterija na više naponskih razina distribucijske mreže s ciljem poboljšanja tehničkih i ekonomskih karakteristika sustava. Ključna svrha je dodatno smanjenje gubitaka radne snage i poboljšanje naponskog profila uz kontrolu investicijskih troškova. Zbog kompleksnosti sustava s transformatorima i različitim naponskim razinama razvijena je nova metoda optimizacije koja uzima u obzir gubitke na transformatorima i utjecaj na napone na različitim naponskim razinama. Simulacije su pokazale da ovaj pristup može značajno unaprijediti učinkovitost razmještaja distribuiranih izvora i kondenzatorskih baterija u odnosu na tradicionalne metode koje
uzimaju u obzir samo impedancije, gubitke i nadomjesne modele mreže jedne naponske razine. Također, pokazano je da pristup s uključivanjem modela transformatora i razmatranjem utjecaja distribuiranih izvora i kompenzacijskih prigušnica može poboljšati performanse kod distribucijskih sustava s problemima porasta napona. Ovaj pristup može se koristiti i za razmještaj prigušnica uz
distribuirane izvore, a ne samo kod kondenzatorskih baterija. Naglašena je važnost preciznog modeliranja svih elemenata distribucijske mreže. Rezultati istraživanja nude smjernice te ukazuju na potencijal daljnjeg razvoja i primjene u elektroenergetskim sustavima. Rad pridonosi razvojem nove metode optimizacije razmještaja distribuiranih izvora i kondenzatorskih baterija u distribucijskim mrežama s više naponskih razina. Ključni doprinosi uključuju modifikaciju genetskog algoritma za bolji razmještaj izvora i baterija, integraciju modela transformatora te ekonomsku evaluaciju. Ovaj rad pruža temelj za buduća istraživanja i inovacije u optimizaciji distribucijskih mreža.This doctoral dissertation explores the optimal placement of distributed generation and capacitor banks across multiple voltage levels of the distribution network, aiming to enhance the technical and economic characteristics of the system. The objective is to reduce real power losses and improve the voltage profile while controlling investment costs. Due to the complexity of systems involving transformers and various voltage levels, a new optimization method has been developed that accounts for transformer losses and voltage impacts across different levels. Simulations show that this approach significantly improves the efficiency of distributed generation and capacitor bank placement compared to traditional methods, which consider only impedance, losses, and equivalent models for a single voltage level. Additionally, it has been shown that including transformer models and considering the impact of distributed generations and shunt reactors enhances performance in systems with voltage rise issues. This approach applies to the placement of shunt reactors alongside distributed generations, not just capacitor banks. Precise modeling of all network elements is emphasized. The research results offer guidelines and suggest potential for further development in power systems. This dissertation contributes by developing a new optimization method for placing distributed generations and capacitor banks in multi-voltage-level networks. Key contributions include the modification of genetic algorithms, integration of transformer models, and economic evaluation. This research provides a foundation for future studies and innovations in network optimization