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Influence of the reaction parameters on the biodiesel synthesis from palm oil and selected straight-chain alcohols
No full textKroz posljednjih nekoliko desetljeća znanost se intenzivnije posvetila razvoju biogoriva s ciljem smanjenja onečišćenja okoliša uzrokovanog izgaranjem fosilnih goriva. Isto tako, porast broja svjetske populacije, brza industrijalizacija, urbanizacija, samo su neki od čimbenika koji uzrokuju rastuću potražnju za energijom i time potiču sve veću upotrebu fosilnih goriva. Kako su fosilna goriva neobnovljivi izvori energije, istraživanja su usmjerena na gorivo koje bi potjecalo isključivo od obnovljivih izvora. Kao dobra alternativa pokazao se biodizel zbog svoje ekološki prihvatljive prirode. Dobiva se katalitičkom transesterifikacijom – reakcijom biosirovine (biljnih ulja i životinjskih masti) s alkoholom uz prisutnost katalizatora. Sastavni dio masti i ulja su trigliceridi – esteri alkohola glicerola i viših masnih kiselina koji sudjeluju u reakciji transesterifikacije s alkoholom. Nastaju smjese alkilnih estera masnih kiselina (biodizel) i alkohol glicerol kao sporedni produkt. U ovom je radu biodizel sintetiziran transesterifikacijom iz palminog ulja kao glavne biosirovine te odabranih ravnolančanih alkohola: 1-propanola, 1-butanola, 1-pentanola, 1-heksanola, 1-oktanola uz prisutnost baznog katalizatora - kalijeva hidroksida (KOH), budući da svojstva primjene biodizela ovise o strukturi reaktanata korištenih u sintezi. Praćeni su utjecaji određenih parametara na reakciju sinteze, a to su: reakcijsko vrijeme (5, 15, 60 minuta), temperatura
(60 °C), molarni omjer alkohola i ulja (5:1 i 10:1) i maseni udio katalizatora (1 mas.% KOH i 3 mas.% KOH). Osim utjecaja navedenih parametara, praćen je i utjecaj molekulske mase alkohola na iskorištenje reakcije. S obzirom na navedene alkohole, u reakciji sinteze biodizela nastaju propilni, butilni, pentilni, heksilni i oktilni esteri masnih kiselina. Dobiveni rezultati pokazuju da reakcijsko vrijeme ima vrlo malo ili nimalo utjecaja na iskorištenje. Povećanje masenog udjela katalizatora i molarnog omjera alkohola i ulja generalno dovodi do većeg iskorištenja sinteze biodizela. S povećanjem molekulske mase alkohola pada polaritet alkohola, a u konačnici i alkoksidnog aniona koji ima glavnu ulogu u mehanizmu bazne transesterifikacije. Padom polariteta alkoksidnog aniona pada i njegov afinitet prema esterskoj skupini triglicerida i time se iskorištenje reakcije smanjuje.Over the past few decades, science has devoted itself more intensively to the development of biofuels with the aim of reducing environmental pollution caused by the burning of fossil fuels. Likewise, the increase in the number of the world's population, rapid industrialization, urbanization, are just some of the factors that cause the growing demand for energy and thus encourage the ever-increasing use of fossil fuels. As fossil fuels are non-renewable sources of energy, researches aimed for fuel that would come exclusively from renewable sources. Biodiesel proved to be a good alternative due to its environmentally friendly nature. It is obtained by catalytic transesterification - the reaction of feedstocks (vegetable oils and animal fats) with an alcohol in the presence of a catalyst. An integral part of fats and oils are triglycerides - esters of glycerol and fatty acids that participate in the transesterification reaction with an alcohol. Therefore, fatty acid alkyl esters (biodiesel) and also alcohol glycerol as a by-product are produced. In this work, biodiesel was synthesized by base – catalyzed transesterification from palm oil as the main feedstock and selected straight-chain alcohols: 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-octanol, in the presence of a base catalyst - potassium hydroxide (KOH), since the application properties of biodiesel depend on the structure of the reactants used in the synthesis. The effects of certain parameters on the synthesis reaction were monitored: reaction time (5, 15, 60 minutes), temperature
(60 °C), molar ratio of alcohol and oil (5:1 and 10:1) and mass fraction of catalyst
(1 wt.% KOH and 3 wt.% KOH). In addition to the influence of the mentioned parameters, the influence of the molecular weight of alcohol on the reaction conversion was investigated, as well. With regard to the mentioned alcohols in the biodiesel synthesis reaction, fatty acid propyl, butyl, pentyl, hexyl and octyl esters were produced. The obtained results show that the reaction time has very little or no influence on the reaction conversion. Increasing the mass fraction of the catalyst and the molar ratio of alcohol to oil generally leads to a higher reaction conversion. As the molecular weight of the alcohol increases, the polarity of the alcohol decreases, and ultimately of the alkoxide anion, which plays a major role in the base transesterification mechanism. As the polarity of the alkoxide anion decreases, its affinity towards the ester group of triglycerides also decreases, and thus the conversion of the reaction decreases
Hunter gatherers’ diet across the Pleistocene – Holocene transition on the eastern Adriatic coast – mammal and mollusc assemblages from Vlakno cave on Dugi Otok
No full textDoktorski rad temeljen je na arheozoološkoj analizi sisavaca i mekušaca iz špilje Vlakno na Dugom otoku. Predmetni lokalitet ima neporemećeni stratigrafski slijed prijelaza iz pleistocena u holocen, a u analizi su obuhvaćeni stratumi iz navedenih razdoblja čija usporedba daje potpunije podatke o strategijama preživljavanja ljudskih grupa koje su koristile ovu špilju. Krajem pleistocena, podizanjem razine mora, istočnojadranska obala postupno mijenja geomorfologiju, što izravno utječe na strategije opstanka tadašnjih lovaca skupljača. Hipoteza istraživanja je da su se lovci skupljači na istočnojadranskoj obali prilagođavali promjenjivim prehrambenim resursima širenjem prehrambene baze na manje sisavce i mekušce. Cilj istraživanja je razumijevanje adaptivnih sposobnosti lovaca skupljača na prijelazu iz pleistocena u holocen na istočnojadranskoj obali, kroz proučavanje promjena u prehrani u tom razdoblju. Interpretacija rezultata temeljena je na skupovima nalaza sisavaca i mekušaca na predmetnom lokalitetu, nakon čega su dobiveni rezultati stavljeni u širi kontekst spoznaja o promjenama u prehrani na istočnoj jadranskoj obali.The transition from the Pleistocene to the Holocene was a dynamic period characterized by a series of climatic and ecological changes that influenced the way of life of hunter-gatherer populations. During this period, the eastern Adriatic coast gradually underwent geomorphological transformations, losing a large part of its landmass. The submergence of the Adriatic plain led to the loss of grassy steppes with mixed low vegetation for ungulates. The gradual isolation of the island of Dugi otok and nearby islands from the mainland limited the migrations of larger herbivores towards the todays islands. On the other hand, marine resources became increasingly accessible, so it can be assumed, based on the revolution of a broad spectrum and optimal foraging theory, since their representation increased towards younger periods. Taking into account the described changes, the main hypothesis of this research is that the Late Pleistocene and Early Holocene hunter-gatherers in the eastern Adriatic adapted to the changing environmental conditions by exploiting smaller mammals and molluscs due to the decreased availability of larger herbivores. The aim of the research is to understand the adaptive capabilities of the Late Pleistocene and Early Holocene communities through changes in diet, from hunting and gathering methods to food preparation. For the purpose of this doctoral thesis, the bone remains of mammals from Pleistocene layers (5 and 4), as well as the remains of molluscs, crabs, and sea urchins from Pleistocene (5 and 4) and Holocene layers (3 and 2) in the Vlakno cave on Dugi otok (Dalmatia, Croatia) were analyzed. The faunal remains underwent taxonomic and taphonomic analysis. The energy input of identified prey from Vlakno was estimated based on the kilocalories they provided. The results of the analysis provide insights into the paleoecological picture, changes in prey/food selection, survival strategies, and the use of the cave during the transition from the Pleistocene to the Holocene. The purpose of this discussion is to outline the subsistence patterns of the huntergatherer groups that used this archaeological site, searching for changes or continuities in the strategiesfor the preparation and consumption of mammals and molluscs in the different layers. Based on the paleoecological and palaeoeconomic data from the faunal assemblage from Vlakno, an estimate was made of the importance of different terrestrial and marine animal resources in the late Pleistocene and early Holocene.
Paleoecological indicators suggest that the environment near Vlakno, i.e., Dugi otok, has changed from the Late Pleistocene to the Holocene. The Late Pleistocene fauna from the Vlakno cave indicates a greater availability of open forests and steppe areas. The rising sea level and gradual submergence of the low-lying areas are also reflected in the changing set of animal remains in Vlakno. Large herbivores (bovids, equids) that inhabited steppe expanses are absent in the Holocene layers, and the representation of species inhabiting open areas with groves increases. The changes recorded in the paleoecology of Vlakno are identical to those found in the rest of the eastern Adriatic coast. According to malacological samples, the immediate vicinity of the cave was characterized by more open and karst areas in the early Holocene. Comparing the Pleistocene and Holocene layers, there is a clear difference in prey selection. The Pleistocene layers abound with remains of red deer (Cervus elaphus), along with foxes (Vulpes vulpes) and hares (Lepus europaeus), and significant sources of meat are also represented by bovids and equids. In the Holocene layers, small game becomes more prevalent, and the more frequent use of marine resources (marine molluscs and fish) indicates a gradual adaptation of hunter-gatherer communities by expanding their food base. The treatment of large herbivore carcasses shows similar practices throughout all the layers, primarily involving dismembering the bodies for easier transport, and mostly transporting whole animals to the cave. It is likely that small game was transported in pieces and processed at the site. Based on the assemblage of mammal and mollusc remains, in combination with lithic indicators, it can be concluded that the Vlakno cave exhibits characteristics of a residential camp that was presumably used for the majority of the year, but mainly during autumn, winter, and spring. The zooarchaeological analysis of the mammal and mollusc remains showed that the indicators of a broad-spectrum revolution are visible in Vlakno as well as along the entire eastern Adriatic coast. Although they share certain commonalities, the eastern Adriatic sites have their own microlocation specificities that significantly influenced the adaptation strategies of survival in the area
Flow spiral freezer for food products
No full textU ovom radu proučavaju se tehnologije konzerviranja hrane zamrzavanjem s fokusom na
zamrzavanje u struji hladnog zraka. Fizikalno će se objasniti zašto su upravo IQF zamrzivači,
među koje spada i protočni spiralni tunel za duboko zamrzavanje, jedni od najkorištenijih
zamrzivača u prehrambenoj industriji. Nadalje se objašnjavaju ključne komponente spiralnog
zamrzivača te se za njega određuje toplinsko opterećenje. Naglasak rada je na osmišljavanju
rashladnog procesa za zamrzavanje 2000 kg/h piletine za postrojenje u Varaždinu. Rad sadržava
termodinamički proračun komponenata rashladnog sustava te odabir istih.This thesis examines conservation technologies with a focus on freezing in a cold air stream. It
will physically explain why IQF freezers, including the flow spiral tunnel for deep freezing, are
among the most widely used freezers in the food industry. Furthermore, the key components of
the spiral freezer are explained, and its thermal load is determined. The focus of this paper is on
designing the refrigeration process for the required production capacity of 2000 kg/h of chicken
for the facility in Varaždin. The paper includes a thermodynamic calculation of the refrigeration
system components and their selection
Analysis of residual stresses in aluminium alloy T-joints made by AC MIG and DC MIG process
No full textZavršni rad obrađen je teorijski i eksperimentalno. U teorijskom dijelu naglasak je na zaostalim naprezanjima kao neizbježnoj pojavi koja se pojavljuje u materijalu kao posljedica zavarivanja. Prikazana su svojstva i karakteristike materijala uzoraka u eksperimentalnom dijelu, te su opisani postupci AC i DC MIG zavarivanja. Objašnjeni su razlozi nastanka zaostalih naprezanja nakon zavarivanja kao i svojstva materijala koja utječu na njih. Prikazana je raspodjela zaostalih naprezanja na zavarenim spojevima uz probleme koje uzrokuju te se predstavljene mjere za smanjenje zaostalih naprezanja. Ukratko su opisane najčešće metode mjerenja zaostalih naprezanja, uz naglasak na metodu rendgenske difrakcije.
U eksperimentalnom dijelu provedeno je mjerenje zaostalih naprezanja metodom rendgenske difrakcije na dvama uzorcima zavarenim AC MIG odnosno DC MIG postupkom. Provedena je analiza rezultata te su dobivene distribucije zaostalih naprezanja shodno literaturi. Usporedbom rezultata AC i DC MIG-a mogu se uočiti različiti iznosi i raspodjela zaostalih naprezanja. Provedeno je elektropoliranje uzoraka te analiza dobivenih rezultata.The topic of this final paper was addressed both theoretically and experimentally. The theoretical part focuses on residual stresses as an inevitable phenomenon occurring in materials after welding. Initially, the materials used for the experimental samples are presented, followed by a description of AC and DC MIG welding processes. The reasons for the formation of residual stresses after welding and the material properties that influence them are explained. The distribution of residual stresses is shown, along with the problems they cause, and measures for their mitigation are discussed. The most common methods for measuring residual stresses are briefly described, with an emphasis on the X-ray diffraction method, its working principle, and basic classification, which was utilized in the experimental part of the work.
In the experimental part, residual stress measurements were performed using the X-ray diffraction method on two samples, one welded using the AC MIG process and the other using the DC MIG process. The results were analyzed, and residual stress distributions were obtained according to the literature. By comparing the results of AC and DC MIG, different amounts and distributions of residual stress can be observed. Electropolishing of the samples was performed and the results obtained were analyzed
Stress analysis of the transformer’s anchoring system due to earthquake
No full textTema ovog završnog rada je analiza naprezanja sidrenog sustava transformatora uslijed potresa. Cilj rada je provesti računalnu analizu naprezanja dna transformatora uslijed djelovanja potresnog opterećenja kako bi se provjerio jedan od sustava sidrenja transformatora unutar tvrtke Končar D&ST. Analiza je provedena uz pomoć dinamičkih modula programskog paketa Abaqus. Rad se sastoji od 6 poglavlja koja zaokružuju cijelu tematiku vezanu uz naziv rada. U prvom poglavlju je napravljen pregled tematike energetskog sustava kako bi se shvatila uloga transformatora u istom. U drugom poglavlju je transformator podijeljen na aktivni te na pasivni dio kako bi se objasnila zadaća pojedinih dijelova transformatora. Treće poglavlje je svojevrsni preglednik najvažnijih pojmova vezanih za potrese. Problematika četvrtog poglavlja su vrste analiza potresnih opterećenja, kao podsjetnik na važnost i prednost numeričkih analiza unutar programskih paketa koji olakšavaju svakodnevnu inženjersku praksu. Posljednja dva poglavlja su vezana uz numeričku analizu te zaključke koji su izvedeni na temelju dobivenih rezultataThe topic of this final thesis is stress analysis of the transformer’s anchoring system due to earthquake. The aim of this paper is computer analysis of the Končar D&ST transformer’s tank bottom, due to earthquake load. The analysis was provided by dynamic modules in Abaqus software package. The paper is composed of six chapters, which round off the mentioned topic. In the first chapter, review of the whole energetic system was done, as well as clearing up the function of the transformer. In the second chapter transformer is divided on active and passive parts, which are all explained in details. In the third chapter, most important concepts of earthquake are described. Different types of earthquake load analyses are presented in chapter four, pointing out importance and benefits of numerical analysis, incorporated in software packages, which make engineer’s working days easier. The last two chapters are dedicated to the numerical analysis and conclusions, based on acquired results
A survey of tick species in Sjeverovac, Sunja
No full textKrpelji su mali ektoparazitske hematofagne grinje koji pripadaju redu Ixodida. Poznato je da
su oni uzročnici i prijenosnici uzročnika bolesti. Između ostalog, ti uzročnici uključuju viruse,
bakterije, protiste i metozoe. Iako nisu sve vrste krpelja i svi krpelji unutar vrste vektori,
uvijek postoji potencijalna opasnost za zdravlje u ubodu koji može dovesti do bolesti. Kod
domaćih životinja bolesti koje prenose krpelji mogu uzrokovati velike ekonomske gubitke,
dok kod ljudi velike zdravstvene probleme, uključujući paralizu i smrt. Dakle, prepoznavanje
vrste krpelja može dati uvid u potencijalne uzročnike koji mogu biti preneseni na domaće
životinje, pa čak i ljude.
Cilj ovog istraživanja bio je istražiti raznolikost i morfologiju vrsta krpelja trenutno prisutnih
u Sjeverovcu, Sunja, nudeći pri tome kritički uvid u njihove ekološke uloge i potencijalne
utjecaje na zdravlje. Krpelji su prikupljeni „dragging“ metodom na tri lokacije u Sjeverovcu.
Ukupno je sakupljeno i identificirano četiri vrste krpelja od ukupno 134 jedinke: Ixodes
ricinus (88,06%), Dermacentor marginatus (5,97%), Dermacentor reticulatus (4,48%) i
Haemaphysalis concinna (1,49%). Rezultati ovog istraživanja su dali, početni temeljni
pregled o tome koliko i kojih vrsta krpelja trenutno ima na području Sjeverovca, pridonoseći
pri tome budućim istraživanjima o raznolikosti krpelja, ekologiji i potencijalnim
zdravstvenim posljedicama.Ticks are small ectoparasitic, hematophagous mites that belong to the order Ixodida. They are
known to be causative agents and vectors of various caustive agents of diseases. Among these
causative agents are viruses, bacteria, protista and metozoa. While not every tick species and
every tick within the species are vectors, there is always a potential health risk associated
with a tick bite, which can lead to disease. In domestic animals, tick-borne diseases can cause
significant economical losses, while in humans, they can lead to major health issues,
including paralysis and death. Thus, identifying tick species can give insight into the potential
causative agents that can be transmitted to domestic animals, and even humans.
The aim of this study was to investigate the diversity and morphology of tick species
currently present in Sjeverovac, Sunja, offering critical insights into their ecological roles and
potential health impacts. Ticks were collected using the drag sampling method across three
locations within Sjeverovac. A total of four species out of 134 specimens were collected and
identified: Ixodes ricinus (88.06%), Dermacentor marginatus (5.97%), Dermacentor
reticulatus (4.48%) and Haemaphysalis concinna (1.49%). The results of this research
provided an initial basic overview of the number and species of ticks currently present in the
Sjeverovac area, contributing to future research on tick diversity, ecology and health-related
implications
Optimisation of layup and layer orientation of the Formula Student composite chassis
No full textU ovom radu je prikazan pregled pravilnika, opis korištenih materijala i teorija iza proračuna kompozitnih struktura. Također, prikazana je strukturalna razrada monokoka Formula Student bolida. Strukturalna razrada uključuje proračun rasporeda slojeva metodom konačnih elemenata, izradu i ispitivanje uzoraka strukture šasije te proračun jednakovrijednosti odabrane kompozitne strukture u odnosu na pravilnikom definiranu čeličnu cijevnu šasiju. Detaljno su opisani koraci pri odabiru rasporeda slojeva monokoka te proračunati svi dijelovi nove, odabrane kompozitne strukture monokoka. Ispitivanjima uzoraka i proračunima dokazana je sigurnost monokoka i samim time vozača koji će voziti bolid. Konačno, provedena je analiza metodom konačnih elemenata torzijske krutosti šasije i naprezanja šasije kod različitih uvjeta vožnje bolida.This paper presents an overview of the regulations, a description of the materials used, and the theoretical background behind the calculation of composite structures. It also includes the structural development of a Formula Student monocoque chassis. The structural analysis involves the calculation of the layup using the finite element method, fabrication and testing of chassis structure samples, as well as the equivalence analysis of the selected composite structure in comparison to the steel space frame defined by the regulations. The steps taken in selecting the monocoque layer configuration are described in detail, and all components of the newly selected composite monocoque structure are calculated. Through sample testing and analytical calculations, the safety of the monocoque and consequently, the safety of the driver has been demonstrated. Finally, a finite element analysis of the chassis torsional stiffness and stress distribution under various driving conditions was performed
Application of Lean tools in manufactuirng
No full textTema ovog završnoga rada je primjena Vitkih (Lean) alata u proizvodnji. U prvom dijelu rada
detaljno je opisan procesni pristup poduzeću, karakteristike takvog pristupa i njegove prednosti
u odnosu na druge organizacijske strukture. Nadalje, objašnjeni su načini praćenja provedbe
procesa te detaljan opis Lean alata, korištenih za poboljšanje proizvodnog procesa.
U praktičnom dijelu rada će se na primjeru jednog poduzeća detaljno prikazati princip primjene
Lean alata: 5S i Poka Yoke. 5S se uvodi s ciljem za sortiranje, čišćenje i standardizaciju, dok
Poka Yoke služi za eliminiranje gubitaka tako da se spriječi greška operatera. Alati se uvode s
ciljem postignuća veće efikasnosti procesa te bolje kvalitete proizvoda.
Na kraju rada predstavljeni su standardizirani predlošci implementacije alata te kvantificirane
uštede nakon primjene navedenih alata Lean menadžmenta.Main topic of this paper is the application of Lean tools in manufacturing. In the first part of
the paper, process approach is explained in detail. its characteristics and advantages to other
organizational structures. Furthermore, methods for tracking the succes of process
implementation will be explained, along with the detail explanation of Lean Tools, used for
improving the manufacturing process.
In the practical part of the paper, the implementation of two Lean tools will be shown: 5S and
Poka Yoke. 5S is used for sorting, cleaning and standardization, while the purpose of the Poka
Yoke tool is to eliminate defects by minimizing the human error. Main purpose of the
implementation is to achieve increased efficiency of the process and better quality of the
products.
At the very end, standardized templates for implementation will be presented, along with the
estimated savings after the implementation of mentioned Lean Tools
Application of generative artificial intelligence in the maintenance of technical systems
No full textOvaj završni rad analizira primjenu generativne umjetne inteligencije u održavanju tehničkih sustava. U uvodnom dijelu prikazan je povijesni razvoj strategija održavanja, kao i razvoj umjetne inteligencije. Središnji dio rada usmjeren je na primjenu genera tivne umjetne inteligencije u održavanju tehničkih sustava, prikazujući najznačajnije prednosti i izazove, dva praktična primjera i analizu jednog komercijalnog softverskog rješenja. Dva praktična primjera ilustriraju rješavanje problema klasifikacije stanja opreme primjenjujući ChatGPT. U prvom primjeru stanje opreme klasificirano je prema normi ISO 10816, dok su u drugom primjeru korišteni stvarni podaci prikupljeni s pomoću senzora. Analiza Senseye Predictive Maintenance, komercijalnog softverskog rješenja koje primjenjuje umjetnu inteligenciju za prediktivno održavanje, ostvarena je u suradnji sa Siemens Hrvatska. Na kraju rada izveden je zaključak o primjeni generativne umjetne inteligencije u održavanju tehničkih sustava.This bachelor's thesis analyses the application of generative artificial intelligence in the maintenance of technical systems. The introductory part presents the historical development of maintenance strategies, as well as the development of artificial intelligence. The central part of the thesis focuses on the application of generative artificial intelligence in the maintenance of technical systems, presenting the most significant advantages and challenges, two practical examples, and an analysis of a commercial software solution. The two practical examples illustrate the solution of the equipment condition classification problem using ChatGPT. In the first example, the equipment condition is classified according to the ISO 10816 standard, while the second example used real data collected using sensors. The analysis of Senseye Predictive Maintenance, a commercial software solution that applies artificial intelligence for predictive maintenance, was conducted in collaboration with Siemens Croatia. At the end of the thesis, a conclusion is drawn on the application of generative artificial intelligence in the maintenance of technical systems
Impact of characteristic of electronic scolarly journals on digital archiving management
No full textUvidom u obilježja elektroničkih znanstvenih časopisa koji su počeli izlaziti 2012. godine, u radu su identificirane i istražene one kategorije časopisa koje su najugroženije glede dugoročnog očuvanja, pri čemu su usporedno analizirani digitalno arhivirani i nearhivirani časopisi. Cilj rada bio je utvrditi vezu između određenih obilježja znanstvenih časopisa i njihova digitalnog arhiviranja. Deskriptivna obilježja znanstvenih časopisa preuzeta su iz baze Ulrichsweb, dok je status o digitalnom arhiviranju časopisa provjeravan u registru Keepers. Bibliometrijska analiza časopisa provedena je prema pokazateljima iz baze podataka Web of Science. Kategorizacija izdavača ispitivanih časopisa, kao i agencija za arhiviranje, provedena je temeljem podataka dobivenih anketnim upitnikom te temeljem relevantne literature. Ishodima istraživanja dobivena su saznanja o digitalnom arhiviranju znanstvenih časopisa, a na temelju kategorizacije časopisa, izdavača te agencija za arhiviranje, predložen je model primjerenosti agencija za arhiviranje pojedinoj kategoriji izdavača, odnosno časopisa.The thesis provides an insight into the characteristics of electronic scholarly journals published since 2012. It identifies and examines the categories of journals that are most at risk in terms of long-term preservation, by analysing digitally archived and non-archived journals. The aim of this thesis is to determine the relationship between the characteristics of scholarly journals and their digital archiving. The descriptive characteristics of scholarly journals were obtained from the Ulrichsweb database, while the digital archiving status of the journals was checked in the Keepers Registry. The bibliometric analysis of the journals was carried out using indicators from the Web of Science database. The categorisation of the publishers of surveyed journals as well as archiving agencies, was based on the data from the questionnaire, as well as on relevant literature. The results of the research expand the knowledge about digital archiving of scientific journals. Based on the categorisation of scholarly journals, publishers and archiving agencies, a suitability model for archiving agencies and particular categories of publishers or journals is proposed