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Permeability control of die-cast aluminium alloy castings
No full textTlačno lijevani odljevci nemaju sasvim homogenu strukturu. Legure u rastaljenom stanju sadrže plinove i oksidne uključke koji mogu izazivati mikropukotine te poroznost kod gotovih odljevaka. Ako se od neke komponente očekuje sposobnost zadržavanja nekog medija (vode, zraka, ulja i sl.), zahtijeva se kontrola propusnosti medija kroz stijenke. Za kontrolu propusnosti tlačno lijevanih odljevaka izrađuju se posebni namjenski uređaji.
U okviru rada opisan je proces tlačnog lijevanja i konstrukcija kalupa za tlačno lijevanje aluminijevih legura. Opisano je kako parametri lijevanja utječu na pojavu propusnosti i koje se još greške na odljevcima mogu pojaviti. Navedene su metode pomoću kojih se ispituje poroznost odljevaka, a na kraju je dan osvrt na ukupne troškove proizvodnje. Teorijska analiza potkrijepljena je primjerom iz industrije.
U zaključku je ukratko objašnjeno koje teme su se obradile u radu i dodani su prijedlozi kako se optimizirao promatrani postupak lijevanja.Die castings do not have a completely homogeneous structure. Alloys, while in a molten state, contain gas bubbles and inclusions that can cause microcracks and porosity in finished castings. If a component is expected to retain a medium (like water, air, oil, etc.) its leak tightness control through the walls is required. Special devices are built to control the leak tightness of die castings.
The thesis describes the process of die casting and the design of molds for die casting of aluminium alloys. It was described how the casting parametres affect the leak tightness and which other defects can occur in castings. The methods used to analyze the porosity of castings were listed and at the end, an overview of the total production costs was given. Theoretical analysis was supported by an example from industry.
In the conclusion, it is briefly explained which topics were covered in the paper and suggestions were added to optimize the observed casting process
Development of a remote-controlled mobile platform for the purpose of cutting the pipes of a nuclear power plant in decommissioning
No full textDekomisija nuklearnih elektrana predstavlja veliki problem u Svijetu. Pojavljuju se problemi
kod načina zbrinjavanja nuklearnog otpada i rušenja građevinskih konstrukcija. U takvoj
opasnoj radnoj atmosferi od velike pomoći pokazali su se daljinski upravljani roboti. Zadatak
diplomskog rada bio je u suradnji s tvrtkom INETEC razviti mobilnu robotsku platformu na
koju se postavlja robotska ruka te koja bi služila za pomoć pri dekomisijskim radovima rezanja
cijevi i skidanja građevinskih dijelova. Prvo su pronađena postojeća rješenja i patenti kako bi
se dobila opća smjernica konstrukcijskom rješenja. Potom su osmišljeni i ocijenjeni koncepti te
je izabran koncept s najvišim ocjenama. Izabrani koncept razrađen je u CAD programu
Inventor. Konačni model sastoji se od četiri podizne gusjenice koje omogućuju kretanje
robotskog sustava u svim smjerovima te ima dodan stabilizacijski mehanizam za dodatnu
sigurnost od prevrtanja.Decommissioning nuclear power plants presents a significant problem worldwide. Issues arise
with the disposal of nuclear waste and the demolition of structural constructions. In such a
hazardous work environment, remotely operated robots have proven to be of great assistance.
The objective of the thesis was to collaborate with the company INETEC in developing a
mobile robotic platform equipped with a robotic arm, which would aid in decommissioning
tasks such as cutting pipes and removing building components. Existing solutions and patents
were initially researched to provide a general guideline for the design solution. Subsequently,
concepts were devised and evaluated, and the concept with the highest ratings was selected.
The chosen concept was further developed using the CAD program Inventor. The final model
consists of four lifting caterpillar tracks that enable the movement of the robotic system in all
directions, and a stabilizing mechanism has been added to enhance safety and prevent
overturning
Determination of volatile organic compounds from air by gas and liquid chromatography
No full textLakohlapivi organski spojevi (VOC) široko su rasprostranjeni u okolišu te su prisutni u velikom broju. U zatvorenim prostorima njihova je koncentracija značajno povišena u odnosu na koncentracije u vanjskom zraku zbog čega imaju negativan utjecaj na kvalitetu zraka i ljudsko zdravlje. Njihovi su izvori brojni, od prirodnih do antropogenih, a problem u zatvorenim prostorima stvaraju zbog isparavanja iz građevinskih materijala, namještaja, sredstava za čišćenje, otpuštanja tijekom kuhanja, grijanja, korištenja proizvoda za osobnu njegu i sl.
Zbog mogućih štetnih utjecaja na zdravlje, Svjetska zdravstvena organizacija (WHO) i razne regulatorne agencije diljem svijeta (EPA, OSHA, DFG) propisuju smjernice i granične vrijednosti za dopuštene koncentracije lakohlapivih organskih spojeva u zatvorenim prostorima. Ovaj je rad bio usmjeren na razvoj i optimizaciju analitičke metode za određivanje deset lakohlapivih organskih spojeva u zraku u zatvorenim prostorima primjenom termalne desorpcije u kombinaciji s plinskom kromatografijom i plameno-ionizacijskim detektorom
(TD-GC-FID). Optimizacija metode uključivala je ispitivanje parametara headspace ekstrakcije, temperatura i vrijeme inkubacije, kao i optimizaciju parametara protoka i volumena uzoraka zraka prilikom uzorkovanja. Cilj istraživanja bio je poboljšati osjetljivost metode i osigurati pouzdanu detekciju lakohlapivih organskih spojeva.Volatile organic compounds (VOCs) are widely distributed in the environment and present in significant numbers. In indoor spaces, their concentrations are significantly higher compared to outdoor air, which negatively affects air quality and human health. Their sources are diverse, ranging from natural to anthropogenic, and in indoor environments, they pose a problem due to evaporation from building materials, furniture, cleaning products, and emissions released during cooking, heating, and the use of personal care products. Due to their potential health hazards, the World Health Organization (WHO) and various regulatory agencies worldwide (EPA, OSHA, DFG) have established guidelines and limit values for acceptable concentrations of VOCs in indoor environments. This study focused on the development and optimization of an analytical method for the determination of ten volatile organic compounds in indoor air using thermal desorption combined with gas chromatography and a flame ionization detector (TD-GC-FID). The method optimization involved investigating headspace extraction parameters, such as incubation temperature and time, as well as optimizing sampling parameters, including airflow rate and sample volume. The aim of the research was to enhance the method's sensitivity and ensure reliable detection of volatile organic compounds
Emerging contaminants in water
No full textNove onečišćujuće tvari u vodama su kemijski spojevi čija je prisutnost u vodama tek otkrivena ili je tek otkriven njihov štetan utjecaj na ljudsko zdravlje i okoliš. Sadržane su u proizvodima koji se svakodnevno koriste, a radi manjka istraživanja i znanja o njima, ne postoji mnogo zakonskih regulativa. To sve doprinosi njihovoj širokoj prisutnosti. Glavni izvor novih onečišćujućih tvari u vodama su postrojenja za pročišćavanje otpadnih voda s konvencionalnim obradama koja su nedovoljno prilagođena za uklanjanje novih onečišćujućih tvari što rezultira njihovim ispuštanjem u okoliš. U ovom radu definirane su nove onečišćujuće tvari i njihovi izvori. Kao glavni izvor novih onečišćujućih tvari u vodi, istaknute su otpadne vode i navedene su neke od naprednih fizikalno-kemijskih i bioloških obrada. U preglednom dijelu pobliže su objašnjeni endokrini disruptori i antibiotici, te njihovi štetni utjecaji na zdravlje ljudi i okoliš.Emerging contaminants in water are chemical compounds whose presence in water has just been discovered or whose adverse effect on human health and environment has just been discovered. They are contained in products that are used on a daily basis, and due to lack of research and knowledge about them, there are not many legal regulations. That contributes to their ubiquitous presence. The main source of emerging contaminants in water are wastewater treatment plants with conventional treatments that are inadequate to remove emerging contaminants, resulting in their release into the environment. In this paper, emerging contaminants and their sources are defined. Wastewater is highlighted as the main source of emerging pollutants in water and some of the advanced physico-chemical and biological treatments are listed. In the review section, endocrine disruptors and antibiotics are explained in more detail, as well as their harmful effects on human health and the environment
The connection between implant and abutment in dental prosthetics
No full textU modernoj dentalnoj implantološkoj protetici postoji trend korištenja unutarnjih koničnih konekcija. S obzirom da različiti proizvođači nude različite kutove konusa, najčešće od 1,5° do 45°, postavlja se pitanje biomehaničke uspješnosti pojedinih konekcija pa tako i implantoloških sustava. Veza između nadogradnje i implantata ostvaruje se putem predopterećenja vijka, a otpuštanje tog vijka uslijed cikličkog opterećenja predstavlja najveći mehanički problem ovakvog sustava. U ovom radu, predstavljen je analitički model izračuna sile predopterećenja vijka i momenta otpuštanja sustava te je numeričkim modelom ispitan utjecaj pojedine konekcije na okolnu kost.In modern dental implant prosthetics, there is a trend of using internal conical connections. Given that different manufacturers offer different taper angles, usually from 1.5° to 45°, the question of the biomechanical success of individual connections and thus of implantology systems arises. The connection between the abutment and the implant is realized by screw preload, and loosening of the screw due to cyclic loading represents the biggest mechanical problem for this type of systems. In this thesis, an analytical model for the calculation of screw preload force and the loosening moment of the system is presented. The influence of a few connections on the surrounding bone is examined with a numerical model
Application of Lean principles and tools in product development
No full textKroz ovaj rad bit će opisan životni ciklus proizvoda s posebnim naglaskom na prvu fazu - razvoj proizvoda. Detaljno će se prikazati primjena Vitkog upravljanja na proces razvoja proizvoda putem opisa principa, sistematizacije primjenjivih alata i identifikacije vrsta gubitaka koji se javljaju tijekom procesa. U praktičnom dijelu rada prikazat će se plan razvojnog procesa zajedno s opisom ključnih prekretnica i sustavom kontrole u realnom vremenu, s ciljem sprječavanja nastanka naknadnih gubitaka i iteracija u kasnijim fazama razvoja uzrokovanih greškama.This paper will describe the product life cycle with a specific focus on the first phase - product development. The application of Lean Management to the product development process will be extensively presented through the description of principles, systematization of applicable tools, and identification of types of losses that occur during the process. The practical
part of the paper will present a development process plan, along with a description of key milestones and a real-time control system, aiming to prevent the occurrence of subsequent losses and iterations in later stages of development caused by discrepancie
Influence of diesel-biodiesel blend composition on engine performance characteristics
No full textBiodizel je vrsta goriva koja predstavlja potencijalnu zamjenu konvencionalnom dizelskom gorivu. U ovom radu, u svrhu ispitivanja utjecaja smjese biodizela i dizelskog goriva na karakteristike rada dizelskog motora, sintetizirani su metilni (FAME), propilni (FAPRE), butilni (FABE), pentilni (FAPE) i heksilni (FAHE) esteri masnih kiselina iz otpadnog ulja reakcijom transesterifikacije, nakon čega su pročišćavani i namiješavani u dvokomponentne smjese s konvencionalnim dizelskim gorivom. Dvokomponentnim smjesama biodizela i dizelskog goriva ispitivane su karakteristike rada motora na jednocilindarskom, četverotaktnom, zrakom hlađenom dizelskom motoru s unutarnjim izgaranjem. Pripremljene su smjese FAME, FAPRE, FABE, FAPE i FAHE s dizelskim gorivom u volumnim udjelima biodizela od 5, 10, 20 i 30 %. Mjerenja na motoru provedena su pri tri različite brzine vrtnje motora od 1200, 1600 i 2000 min-1 za tri različita opterećenja motora. Mjerene su i specifične emisije ispušnih plinova s obzirom na ostvarenu snagu motora i njihovi volumni udjeli te temperatura. Dvokomponentnim smjesama biodizela FAPRE i FAPE s dizelskim gorivom u volumnom udjelu biodizela od 10, 20 i 30 % ispitivano je raspršenje za tlak ubrizgavanja od 300, 500 i 700 bara za četiri različite duljine ubrizgavanja u trajanju od 0,6, 0,8, 1 i 3 ms. Smjese su ubrizgavane u stakleni okvir za atmosfersko ubrizgavanje, a domet i kut raspršenja mlaza određivani su sustavom za mjerenje s visokobrzinskom kamerom i laserom. Kako bi se podaci o karakteristikama rada dizelskog motora i raspršenja mogli dodatno potkrijepiti, svim smjesama biodizela i dizelskog goriva te čistim komponentama određene su kinematička viskoznost i gustoća pri četiri različite temperature od 15, 25, 40 i 60 °C. Na temelju provedenog ispitivanja, zaključeno je da je domet smjesa biodizela veći, a kut raspršenja manji u odnosu na čisto dizelsko gorivo zbog veće viskoznosti i gustoće biodizela. Potvrda tome su i podaci dobiveni mjerenjem viskoznosti i gustoće smjesa biodizela i dizelskog goriva. Mjerenjem karakteristika rada motora, dobiveno je da su emisije dušikovih oksida (NOx) i ukupnih ugljikovodika (THC) uglavnom manje, a emisije ugljikovog monoksida (CO) i dioksida (CO2) veće za smjese biodizela u odnosu na čisto dizelsko gorivo.Biodiesel is a type of fuel that represents a potential replacement for conventional diesel fuel. In this work, for the purpose of examining the influence of a mixture of biodiesel and diesel on the performance characteristics of a diesel engine, methyl (FAME), propyl (FAPRE), butyl (FABE), pentyl (FAPE) and hexyl (FAHE) esters of fatty acids from waste cooking oil were synthesized via transesterification reaction, after which they were purified and mixed into two-component mixtures with conventional diesel fuel. Two-component mixtures of biodiesel and diesel were used to test the performance characteristics of a single-cylinder, four-stroke, air-cooled, internal combustion diesel engine. Mixtures of FAME, FAPRE, FABE, FAPE and FAHE with diesel were prepared in biodiesel volume fractions of 5, 10, 20 and 30 %. Measurements on the engine were performed at three different engine speeds of 1200, 1600 and 2000 min-1 for three different engine loads. Specific emissions of exhaust gases were also measured with regards to the achieved engine power and their volume ratios and temperature. Two-component mixtures of biodiesel FAPRE and FAPE with diesel in a volume fraction of biodiesel of 10, 20 and 30 % were tested for dispersion at injection pressures of 300, 500 and 700 bar with four different injection durations of 0,6, 0,8, 1 and 3 ms. The mixtures were injected into a glass frame for atmospheric injection, penetration and angle of the jet dispersion were determined by a measurement system with a high-speed camera and a laser. In order to further support the data on diesel engine operation characteristics and dispersion, kinematic viscosity and density were determined for all biodiesel and diesel mixtures and pure components at four different temperatures of 15, 25, 40 and 60 °C. Based on the conducted test, it was concluded that the range of biodiesel mixtures is greater and the fuel injection angleis lower compared to pure diesel due to the higher viscosity and density of biodiesel. This is confirmed by the data obtained by measuring the viscosity and density of biodiesel and pure diesel mixtures. By measuring the performance characteristics of the engine, it was found that the emissions of nitrogen oxides (NOx) and total hydrocarbons (THC) are mostly lower, and the emissions of carbon monoxide (CO) and dioxide (CO2) are higher for biodiesel mixtures compared to pure diesel
The influence of the feedstock type and reaction parameters on the synthesis of fatty acid pentyl and hexyl esters
No full textReakcijom transesterifikacije u kojoj trigliceridi iz ulja/masti reagiraju s alkoholom u prisutnosti katalizatora dolazi do nastajanja alkilnih estera masnih kiselina, odnosno biodizela. Budući da se dobiva iz obnovljivih izvora, biodizel se dodaje u određenim omjerima u dizelsko gorivo, čime se smanjuje utjecaj na okoliš. Metanol se u odnosu na ostale alkohole najviše upotrebljava u proizvodnji biodizela, međutim biodizel se također može proizvoditi iz viših alkohola čija je prednost što se mogu dobiti iz obnovljivih izvora za razliku od metanola.
U ovom radu provedena je sinteza biodizela bazično kataliziranom transesterifikacijom, u prisutnosti kalijeva hidroksida, s različitim biosirovinama (suncokretovo, repičino, kokosovo, otpadno jestivo ulje i životinjska mast) te upotrebom alkohola 1-pentanola ili 1-heksanola. Istražen je utjecaj različitih reakcijskih uvjeta na iskorištenje reakcije transesterifikacije.
Uvjeti koji su se mijenjali bili su: molarni omjer alkohola i ulja/masti (5:1 i 12:1), vrijeme reakcije (2, 5, 15 i 30 minuta) te maseni udio katalizatora (1 i 3 %). Dobiveni rezultati ukazuju da molarni omjer alkohola i ulja/masti ima najveći utjecaj na iskorištenje reakcije transesterifikacije. Veliki utjecaj na iskorištenje ima i udio katalizatora, dok vrsta biosirovine i vrijeme provedbe reakcije ne utječu značajno na iskorištenje. Iskorištenja dobivena sintezom biodizela iz 1-pentanola i 1-heksanola pri istim uvjetima reakcije imaju slične vrijednosti, ali uočeno je da se povećanjem duljine alkilnog dijela lanca smanjuje iskorištenje korištenjem suncokretovog i repičinog ulja pri omjeru 5:1 s 3 mas.% KOH. Isto tako, vidljivo je da veći udio zasićenih masnih kiselina u sirovini pridonosi višem iskorištenju reakcije. Zadovoljavajuća iskorištenja dobivena su pri molarnom omjeru alkohola i ulja/masti 12:1 i 1 mas.% KOH sintezom iz suncokretovog, repičinog i otpadnog jestivog ulja te životinjske masti, dok su kod kokosovog ulja zadovoljavajuća iskorištenja postignuta korištenjem 5:1 molarnog omjera i 3 mas.% KOH.The transesterification reaction in which triglycerides from oils/fats react with alcohol in the presence of a catalyst leads to the formation of alkyl esters of fatty acids, i.e. biodiesel. Since it is obtained from renewable sources, biodiesel is added in certain proportions to diesel fuel, which reduces the impact on the environment. Compared to other alcohols, methanol is mostly used in the production of biodiesel, but it can also be produced from higher alcohols, the advantage of which is that they can be obtained from renewable sources, unlike methanol. In this work, the synthesis of biodiesel was carried out by base-catalyzed transesterification, in the presence of potassium hydroxide, with different feedstocks (sunflower, rapeseed, coconut, waste cooking oil and animal fat) and using the alcohol 1-pentanol or 1-hexanol. In addition, the influence of different reaction conditions on the yield of the transesterification reaction was investigated. The conditions that were varied were: the molar ratio of alcohol and oil/fat (5:1 and 12:1), the reaction time (2, 5, 15 i 30 minute) and the mass fraction of the catalyst (1 and 3 %). The obtained results indicate that the molar ratio of alcohol and oil/fat has the greatest influence on the utilization of the transesterification reaction. The mass fraction of the catalyst also has a great influence on the conversion, while the type of feedstock and the reaction time do not significantly affect the conversion. The yields obtained by the synthesis of biodiesel from 1-pentanol and 1-hexanol under the same reaction conditions have similar values, but it was observed that increasing the length of the alkyl chain decreases the yield using sunflower and rapeseed oil at a ratio of 5:1 with 3 wt% KOH. Also, it is evident that a higher amount of saturated fatty acids in the feedstock contributes to a higher conversion of the reaction. Satisfactory conversions were obtained at a molar ratio of alcohol and oil/fat of 12:1 and 1 wt% KOH synthesis from sunflower, rapeseed and waste cooking oil and animal fat, while with coconut oil sufficient conversions were achieved using a 5:1 molar ratio and 3 wt% KOH
Anthropogenic pollutants
No full textAntropogene onečišćujuće tvari su tvari prisutne u okolišu nastale uslijed ljudske aktivnosti. Identificirani izvori antropogenih onečišćujućih tvari, poput industrijskih otpadnih tokova i komunalnih otpadnih voda, predstavljaju ključne izazove u očuvanju okoliša. Globalna rasprostranjenost navedenih tvari ukazuje na potrebu za međunarodnom suradnjom i propisima kako bi se suzbile negativne posljedice antropogenog onečišćenja. U okviru rada prikazani su glavni izvori antropogenih onečišćujućih tvari, njihov utjecaj na čovjeka i ostale organizme, njihova rasprostranjenost diljem svijeta te su predstavljeni postupci njihova uklanjanja. Također, istaknuti su farmaceutici kao značajna skupina antropogenih onečišćujućih tvari, s posebnim naglaskom na analgetike i anksiolitike te glavne predstavnike navedenih skupina.Anthropogenic pollutants are substances that are present in the environment as a result of human activities. Identified sources of anthropogenic pollutants, such as industrial waste streams and municipal wastewater, pose a major challenge to environmental protection.
The global distribution of these substances highlights the need for international cooperation and regulation to mitigate the negative impacts of anthropogenic pollution. The paper presents the main sources of anthropogenic pollutants, their effects on humans and other organisms, their global distribution and the methods for their removal. In addition, pharmaceuticals were highlighted as an important group of anthropogenic pollutants, with a focus on analgesics and anxiolytics and the main representatives of these groups
Improving productivity through automation of the manufacturing process
No full textIndustrija 4.0 predstavlja nove mogućnosti, ali i nove izazove za kompanije orijentirane na proizvodnju. Tehnološki napredak donio je sa sobom velik broj noviteta koji mogu biti implementirani u proizvodne sustave s namjerom da ih se modernizira, ubrza te optimizira kako bi mogli polučiti bolje rezultate i tako zadovoljiti sve zahtjevnije tržište. Stoga, kako bi povećale svoju produktivnost mnoge kompanije žele držati korak s trendovima u industriji i tako pokušati ostvariti konkurentsku prednost. Ključ u tome je uvođenje automatizacije u proizvodnju, usporedno s digitalizacijom. Ovaj rad prezentira najvažnije suvremene tehnologije Industrije 4.0 te pobliže prikazuje pristup i strategije uvođenja automatizacije na primjeru iz prakse.Industry 4.0 represents new opportunities, but also new challenges for production-oriented companies. Technological progress has brought with it many novelties that can be implemented in production systems with the intention of modernizing, speeding up and optimizing them so that they could obtain better results and thus satisfy the increasingly demanding market. Therefore, in order to increase their productivity, many companies want to keep up with the trends in the industry and consequently try to achieve a competitive advantage. The key to this is the introduction of automation in production, along with digitalization. This paper presents the most important modern technologies of Industry 4.0 and shows in more detail the approach and strategies of implementing automation on a real example