Croatian Digital Thesis Repository
Not a member yet
259189 research outputs found
Sort by
CAD predložak za pojedine faze proizvodnje vijaka za beton
No full textConcrete screw anchors are well-known fasteners used in industries such as construction, automotive or nuclear. Among cold forming’s different methods, the ones mainly used for producing screw anchors are extrusion and upsetting. Screws must consistently meet the given requirements and perform the way they are meant to in different environments, and that's the task for which multi-stage cold forming is a suitable choice. Multi-stage cold forming is a widely used forming process for efficient and fast mass-production of simple and complex parts with great mechanical properties. Benefits to this forming process are negligible loss of material, good dimensional control, great surface finish, improved strength, and reproducibility. However, the forming sequence must be carefully designed by highly experienced die designers, and it requires both their experienced judgment and the implementation of established design rules. The development of such sequences is being improved through the years. Since one specific screw is designed in a couple of variations, to reduce the total design time, engineers have implemented CAD templates for automatically generating the forming stages for different screw lengths. The final product’s dimensions, tools, and machine parameters are given as an input, and the template outputs the forming part’s dimensions through the stages for different screw sizes and lengths. The template for hexagonal head screw anchors had issues with replicating the part’s dimensions from the machine, i.e., the actual formed stages were not following the computer-generated ones. The initially assumed root causes for the dimension differences were that the volume distribution between the screw’s head and body are not the same for all stages. Likewise, the effects of some machine parameters, such as different ejector positions, were previously not thoroughly examined. Therefore, the main objective of this thesis is to have a better understanding of the volume distribution between the screw’s head and body through the stages, and of the forming process itself. For these reasons, an analysis of the semi-finished screw billets through the stages using precise measurements and numerical analysis is necessary. The effects of different ejector positions were observed on the measurements, and further tested in a numerical analysis tool Deform2D. The necessary adjustments to the template are finally implemented, and the modified template is tested. The modified template had smaller differences to the real parts in comparison to the initial one.Betonski sidreni vijci su dobro poznati spojni elementi korišteni u industrijama kao što su građevinska, automobilna i nuklearna. Između različitih metoda hladnog oblikovanja, one koje se najviše koriste za proizvodnju betonskih vijaka su ekstruzija i sabijanje. Vijci moraju redovito zadovoljavati različite zahtjeve koji se na njih postavljaju i to u različitim okruženjima, a da bi se to postiglo, idealan proces proizvodnje je hladno oblikovanje. Hladno oblikovanje u više faza je često korišteni proces oblikovanja za efikasnu i brzu masovnu proizvodnju jednostavnih i kompleksnih dijelova s odličnim mehaničkim svojstvima. Prednosti ovog procesa su zanemarivi gubitak materijala, dimenzijska točnost, dobra kvaliteta površine, poboljšana čvrstoća i ponovljivost. Međutim, redoslijed operacija mora biti pažljivo oblikovan od strane iskusnih konstruktora alata i zahtjeva njihovu iskustvenu procjenu, kao i implementaciju općih pravila deformiranja. Takvi redoslijedi operacija se poboljšavaju kroz godine. S obzirom da jedan vijak ima nekoliko varijacija veličine, inženjeri su implementirali CAD predloške za automatsko generiranje redoslijeda operacija za različite dužine i veličine vijaka s ciljem smanjenja ukupnog vremena procesa dizajna. Dimenzije gotovog proizvoda i parametri alata i strojeva unose se u predložak, koji onda stvara redoslijed sa svim dimenzijama kroz različite faze, za različite veličine i dužine vijaka. Jedan predložak koji generira vijke sa šesterokutnom glavom nije dobro replicirao dimenzije stvarnog proizvoda, tj. dimenzije na proizvedenim dijelovima nisu u potpunosti odgovarale dimenzijama na predlošku. Inicijalno pretpostavljeni uzroci tog problema su nejednaka distribucija volumena između glave i tijela vijka kroz faze na stvarnim uzorcima. Nadalje, efekti podešavanja nekih parametara strojeva, kao što su pozicije izbacivača, nisu prethodno bile detaljnije ispitane. S obzirom na to, glavni cilj ovog rada je formiranje boljeg razumijevanja distribucije volumena između glave i tijela vijka kroz faze, ali i samog proizvodnog procesa. Iz tih razloga, potrebna je analiza pojedinih poluproizvoda vijaka kroz proizvodne faze uz pomoć preciznih mjerenja uzoraka i numeričke analize. Efekti različitih pozicija izbacivača su prepoznati pomoću mjerenja, i dodatno ispitani uz pomoć alata za numeričku analizu Deform2D. Potrebne promjene na predlošku su u konačnici implementirane, a promijenjeni predložak je ispitan. Novi predložak je imao manje razlike između stvarnih vrijednosti i onih u predlošku u odnosu na inicijalni
SELECTION OF OPTIMAL PRECIPITATING AGENT FOR ZINC REMOVAL FROM AQUEOUS SOLUTIONS BY CHEMICAL PRECIPITATION : bachelor thesis
No full textIndustrijskom revolucijom započelo je intenzivnije onečišćenje okoliša različitim štetnim tvarima. Značajnu ulogu u onečišćenju prirodnih voda imaju industrijske otpadne vode, koje su jedan od glavnih izvora emisije teških metala u okoliš. S ekološkog i zdravstvenog stajališta važno je prije emisije industrijske otpadne vode adekvatno pročistiti. Najčešće metode obrade takvih voda su kemijsko taloženje, ionska izmjena, adsorpcija i membranske tehnike. U ovome radu provedeno je uklanjanje cinka iz vodenih otopina koncentracija 100 mg/L i 500 mg/L metodom kemijskog taloženja uz prethodnu neutralizaciju do pH područja 7,0-7,5; 8,0-8,5 i 9,0-9,5 različitim taložnim sredstvima - suspenzijama vapnenog mlijeka pripravljenim iz tehničkog vapna različite čistoće te natrijevim hidroksidom. Uklanjanje cinka uspješno je provedeno uz neutralizaciju u pH području 9,0-9,5 korištenjem svih ispitanih taložnih sredstava, s ostatnom koncentracijom cinka ispod maksimalno dopuštene. Uzimajući u obzir učinkovitost taložnog sredstva, cijenu te količinu nastalog otpadnog mulja, optimalno taložno sredstvo za ispitane eksperimentalne uvjete je suspenzija vapnenog mlijeka pripravljena iz tehničkog vapna čistoće 94,3%.With the industrial revolution, more intensive environment pollution with various harmful substances began. Industrial wastewaters, as one of the main sources of heavy metal emissions into the environment, play a significant role in the pollution of natural waters. From an ecological and health point of view, it is important to adequately purify industrial wastewaters before emission. The most common methods of their treatment are chemical precipitation, ion exchange, adsorption and membrane techniques. In this bachelor thesis, the removal of zinc from aqueous solutions containing 100 mg Zn/L and 500 mg Zn/L was carried out by chemical precipitation with prior neutralization to a pH ranges of 7.0-7.5; 8.0-8.5 and 9.0-9.5, respectively, using different precipitating agents - milk of lime prepared from technical lime of different purity and sodium hydroxide. Zinc removal was successfully performed with neutralization in the pH range of 9.0-9.5 using all precipitating agents tested, with the residual zinc concentration below the maximum allowed. Taking into account the effectiveness of the precipitating agent, costs and the amount of waste sludge generated, the optimal precipitating agent for the tested experimental conditions is milk of lime prepared from the technical lime with 94.3% of purity
Lokalizacija naspram modularnosti funkcija - studija slučaja oporavka kognitivnog, izvršnog i emocionalnog funkcioniranja nakon operacije tumora mozga
No full textDugo se smatralo da su određene kognitivne funkcije, poput govora, jasno lokalizirane u određenim područjima mozga. Ovaj pristup temelji se na istraživanjima posljedica lokaliziranih oštećenja mozga na osnovi kojih su razvijene teorije o uzročno-posljedičnoj vezi oštećenja ili lezija anatomskih struktura mozga i pripadajućih kognitivnih deficita. U novije vrijeme koncept lokaliziranosti funkcija mijenja se u koncept modularne povezanosti prema kojem je u osnovi kognitivnih funkcija povezani sustav neuralnih mreža. Prema tome, lezija određene strukture mozga ne mora nužno rezultirati deficitom funkcije koja je povezana s tom strukturom. U Klinici za neurokirurgiju KBC-a Zagreb postoji višegodišnja praksa operativnog liječenja u budnom stanju koje za cilj ima maksimalno uklanjanje tumora mozga uz minimiziranje deficita govora i/ili motorike. Cilj ove studije slučaja je prikazati učinak tumorske infiltracije i kognitivno, izvršno i emocionalno funkcioniranje nakon operacije tumora mozga u budnom stanju, a koji je zahvatio govorna područja u čeonom i sljepoočnom režnju lijeve mozgovne polutke kod pacijentice u dobi od dvadeset devet godina koja je kao komorbidno stanje imala i multiplu sklerozu s plakovima obostrano sljepoočno, lijevo parahipokampalno supratentorijski obostrano peritrigonalno, periventrikularno u području centrum semiovale i unutar žuljevitog tijela. Neuropsihologijsko ispitivanje provedeno je u dva navrata. Rezultati su pokazali očuvano govorno funkcioniranje nakon uklanjanja govornih područja. Rezultati su također pokazali očuvano ostalo kognitivno, izvršno i emocionalno funkcioniranje u kojem nije došlo do značajnih promjena u odnosu na predoperativno neuropsihologijsko testiranje. Obrazac kognitivnog funkcioniranja ove ispitanice nakon operativnog liječenja govori u prilog neuroplastičnosti mozga kao i postojanju kompenzatornih mehanizama u mozgu koji uslijed pojave tumora počinju i prije operacijskog liječenja i dodatno se konsolidiraju nakon neurokirurške intervencije stoga nalazi studije govore u prilog i teorije o modularnosti funkcija.Introduction
For much of the 20th century, the brain was viewed as having specialized, localized regions responsible for specific functions, and damage to these areas was thought to cause permanent deficits. This view had significant implications for surgery, suggesting that "eloquent" areas, such as Broca’s or Wernicke’s areas, were non-operable due to their critical functions. However, functional recovery observed after damage to these areas challenged this model, leading to a shift towards a more dynamic understanding of brain function. Recent theories emphasize the brain as a complex, interconnected neural network where cognitive functions are not solely dependent on individual regions but rather on the dynamic interplay between various structures, including cortical-subcortical networks and white matter pathways. Current perspectives on brain connectivity consider the brain as a network of functional areas that interact dynamically, and lesions can disrupt not only the affected region but the entire brain's functional connectivity. This shift in understanding has significant clinical implications, particularly for surgery in areas previously thought to be inoperable. The objective of this work is to explore the evolution of the concept of brain function and dysfunction, the role of brain connectivity and plasticity, and how this knowledge is applied to conditions like brain tumors and multiple sclerosis, as well as recovery following brain injuries.
Aim of the study
The aim of this case study is to examine cognitive, executive, and emotional functioning following brain tumor surgery performed while the patient was awake, where the tumor affected speech areas in the frontal and temporal lobes of the left hemisphere. The patient also had multiple sclerosis as a comorbidity. The study aims to stimulate discussion on various theories of brain processing and functional organization and to provide an overview of the latest neuroscientific perspectives on the impact of brain damage on cognitive functioning.
Methodology
Medical History: The patient is a 29-year-old woman with a co-occurrrence of multiple sclerosis (MS). In June 2021, she experienced left facial muscle weakness, which was later identified as a demyelinating lesion, prompting the diagnosis of relapsing-remitting multiple sclerosis (RRMS). A brain MRI in June 2024 revealed tumor progression in the left frontal lobe, which led to the decision for awake surgery.
Surgical Procedure: The patient underwent surgery using the "awake-asleep-awake" protocol, which involves preparation by various specialists, including neurosurgeons, neurologists, psychologists, speech therapists, and anesthesiologists. Neuropsychological testing was done before surgery to evaluate cognitive, executive, and emotional functioning. If significant cognitive impairment or anxiety was found, the surgery would be changed to general anesthesia.
Preoperative and Postoperative Neuropsychological Evaluation: Preoperative evaluation was carried out over two sessions, starting on the day of hospitalization. Cognitive issues described by the patients were occasional experience described as brain fog, difficulty recalling words, and slowed thinking. A follow-up neuropsychological assessment was conducted 14 weeks after surgery. The patient showed no significant changes in her emotional or cognitive state. The evaluation both times was performed over two sessions to minimize mental fatigue.
Tests Administered: A series of neuropsychological tests were used to assess cognitive, executive and emotional functions: Wechsler Bellevue Intelligence Scale (WB-II). Auditory Verbal Learning Test (AVLT), Rey-Osterrieth Complex Figure Test (RCFT), Trail Making Test (TMT), Boston Naming Test (BNT), Verbal fluency Tests (FAS, animal naming), Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI) with additionally Wisconsin Card Sorting Test (WSCT), Token Test (TT), and subtest from Boston Aphasia Diagnostic Test (BDAE) – Cookie Theft.
Intraoperative Mapping and Awake Phase: The patient underwent a left-sided frontal-temporal craniotomy, followed by the awakening from general anesthesia. The surgery was performed using bipolar stimulation to map motor and speech functions under local anesthesia. A team of neurologists, speech therapists, and psychologists conducted the testing. During the procedure, the patient was asked to count aloud and lift up her right arm to help locate these areas. After testing different cortical areas with stimulation, neurosurgeon identified the primary motor cortex posterior to the tumor, primarily located in the opercular region of the lower frontal gyrus. The tumor was successfully removed without significant damage to key areas. The procedure lasted 5 hours, with the patient being awake for one hour. Pathological analysis confirmed the tumor was an astrocytoma grade II, indicating a slow-growing and less aggressive tumor, which suggests a favorable prognosis.
Results and discussion
Before surgery, the patient exhibited mild cognitive difficulties, including reduced verbal fluency, challenges in sequential thinking and visual attention to details, and slight impairments in parallel processing speed. Fourteen weeks post-surgery, the patient underwent a follow-up neuropsychological evaluation, which revealed no significant cognitive, executive, or emotional changes compared to preoperative functioning. She performed at average levels on most tests assessing memory, verbal conceptualization, attention, visual-spatial abilities, and verbal learning. However, verbal fluency in phonetic categories and visual attention to detail remained impaired. These issues seemed more related to multiple sclerosis (MS) than the tumor's location. The patient reported returning to normal daily and work activities, expressing no significant changes in her emotional or cognitive state. Speech and motor functions were stable, and no rehabilitation was required.
Despite the tumor affecting regions involved in language processing, no significant language deficits were observed. Intraoperative mapping showed speech issues only during stimulation of certain motor cortices, suggesting functional reorganization around the tumor. Functional reorganization, particularly in glioma cases, likely contributed to the preservation of cognitive functions. The tumor's slow growth may have triggered gradual brain network adaptation, including the involvement of remote brain regions and contralateral structures. This concept supports the idea of functional recovery following surgery, which was evident in this patient as she resumed normal work and social activities within two months post-operation.
Furthermore, the patient’s MS contributed to cognitive challenges, particularly with verbal fluency, serial thinking and slightly impaired processing speed, but did not significantly worsen post-surgery. MS-related cognitive impairments tend to progress slowly, with some patients remaining stable for years. Emotional and social functioning were minimally impacted, with the patient reporting normal emotional regulation despite some anxiety and depression. Her ability to cope, family support, and the return to normal activities contributed to improvement in emotional well-being after surgery.
Conclusion
The patient's cognitive and executive functions remained stable post-surgery, with only mild improvements observed. Functional reorganization of the brain, likely triggered by the slow growing glioma, helped preserve critical functions despite tumor removal. Additionally, while multiple sclerosis (MS) contributed to some cognitive challenges, these did not worsen after the surgery. The patient successfully resumed normal social and work activities, and her emotional well-being improved postoperatively, aided by strong family support and coping strategies
Bacterial resistance to antibiotics in Klebsiella and Enterobacter isolates from wastewater treatment plants in Croatia
No full textCilj ovog diplomskog rada je izolirati karbapenem-rezistentne Klebsiella i Enterobacter izolate iz uzoraka otpadne vode iz uređaja za otpadne vode (UPOV-i) grada Splita i morske vode u blizini pripadajućih podmorskih ispusta u srednjem Jadranu, te testirati njihovu fenotipsku osjetljivost na antibiotike. Određena je razina fekalnog onečišćenja u uzorcima te je 108 izolata identificirano do vrste i ispitana njihova fenotipska osjetljivost na 16 antibiotika metodom disk-difuzije na Mueller-Hinton agaru. Najveći broj izolata pokazao je rezistenciju na cefoksitin (97,22%), piperacilin (90,74%), aztreonam (84,26%) i meropenem (79,63%), dok je najmanja učestalost rezistencije zabilježena na trimetoprim-sulfametoksazol (17,59%). Rezultati pokazuju visok postotak rezistencije na različite klase antibiotika, odnosno višestruko rezistentni fenotip izolata i moguću prisutnost karbapenemaza. Također, obzirom da UPOV Katalinića Brig obrađuje i otpadne vode iz KBC-a Split, mogući su rizici širenja bolničkih rezistentnih sojeva u morski okoliš, što potvrđuje potrebu za daljnjim praćenjem njihove učestalosti te nastavkom istraživanja u smjeru određivanja genotipa rezistencije ovih oportunističkih patogena kritičnog prioriteta.The aim of this thesis was to isolate carbapenem-resistant Klebsiella and Enterobacter isolates from wastewater samples from wastewater treatment plants (WWTPs) of the city of Split and seawater from the adjacent submarine outlets in the central Adriatic, and to test their phenotypic sensitivity to antibiotics. The level of fecal contamination in the samples was determined, and 108 isolates were identified to species and their phenotypic sensitivity to 16 antibiotics was tested using the disk-diffusion method on Mueller-Hinton agar. The largest number of isolates showed resistance to cefoxitin (97.22%), piperacillin (90.74%), aztreonam (84.26%) and meropenem (79.63%), while the lowest frequency of resistance was recorded against trimethoprim-sulfamethoxazole (17.59%). The results show a high percentage of resistance to different classes of antibiotics, i.e. the multiple resistant phenotype of the isolates and the possible presence of carbapenemases. Also, considering that UPOV Katalinića Brig also processes wastewater from University Hospital Split, there are possible risks of the spread of hospital resistant strains into the marine environment, which confirms the need for further monitoring of their frequency and the continuation of research in the direction of determining the resistance genotype of these WHO critical-priority opportunistic pathogens
Strukturalna karakterizacija, antimikrobna aktivnost i toksičnost antimikrobnih peptida identificiranih u trakavice (Taenia solium Linnaeus, 1758)
No full textAll living organisms are constantly threatened by large number and great diversity of pathogens which is why all of them synthesize antimicrobial peptides (AMPs) as a first line of defense as a part of their innate immunity. These molecules show direct antimicrobial and/or immunomodulatory properties which make them a potential source of new therapeutics during global antimicrobial resistance crisis. As one of the most successful animal groups in nature, parasitic helminths (worms) found different ways to overcome and avoid expulsion by their host’s immune system. One of them is by secreting different immunomodulatory molecules one of which are also AMPs. Helminth’s coevolution with the host gut microbiome and reciprocal adaptation which favors development of compounds minimally invasive to the host make helminthic AMPs especially interesting for further investigation. The aim of this thesis was to characterize three potential AMPs from tapeworm (Taenia solium). That included bioinformatical analysis, structural characterization by CD spectroscopy, determination of antimicrobial activity and subsequent mode of action by propidium iodide (PI) uptake assay using flow cytometry. Cytotoxic activity was tested with MTT assay and late confirmed with PI uptake assay using flow cytometry. Two out of three peptides showed potent antibacterial activity with borderline levels of toxicity which should be addressed if the peptides undergo further studies for potential therapeutical applications.Svi živi organizmi konstantno su ugroženi velikim brojem i velikom raznolikošću patogena, zbog čega sintetiziraju antimikrobne peptide (AMP) kao prvu liniju obrane i dio svog urođenog imunološkog odgovora. Ove molekule pokazuju izravno antimikrobno i/ili imunomodulacijsko djelovanje što ih čini potencijalnim izvorom novih lijekova tijekom globalne krize razvoja rezistencije na antibiotike. Kao jedna od najuspješnijih životinjskih skupina u prirodi, parazitski crvi su pronašli različite načine da nadvladaju i izbjegnu imunološki sustav svog domaćina. Jedan od njih je izlučivanje različitih imunomodulacijskih molekula kao što su npr. antimikrobni peptidi. Koevolucija parazitskih crva s crijevnim mikrobiomom domaćina i recipročna prilagodba koja pogoduje sekreciji minimalno invazivnih spojeva čini ove antimikrobne peptide posebno zanimljivima za daljnje istraživanje. Cilj ovog rada bio je istražiti biološku aktivnost tri potencijalna AMP-a iz trakavice, Taenia solium. To je uključivalo bioinformatičku analizu, strukturnu karakterizaciju CD spektroskopijom, određivanje antimikrobne aktivnosti i mehanizma djelovanja koristeći propidij jodid i protočnu citometriju. Citotoksična aktivnost ispitana je MTT testovima i kasnije potvrđena koristeći propidij jodid (PI) i protočnu citometriju . Dva od tri peptida pokazala su potencijalno antibakterijsko djelovanje s graničnim razinama toksičnosti koju bi trebalo poboljšati ukoliko se peptidi budu dalje istraživali u svrhu potencijalne terapijske primjene
Testing the stability of fluoride solutions of different concentrations in glass packaging : diploma thesis
No full textStaklo je jedan od najvažnijih materijala u svakodnevnom životu, u kojem se pojavljuje posvuda, a razlog zbog kojeg se tako često koristi je njegova kemijska stabilnost. Kemijski je stabilno zbog svoje amorfne strukture odnosno izostanka pravilnog rasporeda atoma. Iako je staklo otporno na mnoge kemikalije, ono nije univerzalno inertno. Zadatak ovog diplomskog rada je bio u određenom vremenskog periodu, u nekoliko staklenih boca pohraniti različite koncentracije standardne otopine natrijevog fluorida, utvrditi utječe li pohrana tih otopina u staklu na promjenu koncentracije fluorida, odnosno događa li se interakcija otopine (fluorida) sa staklom. U eksperimentu su pripravljene otopine natrijevog fluorida u rasponu koncentracija 1,0×10 --6 do 1,0×10 -2 mol L -1 . Radnim otopinama u svakom mjerenju izmjeren je potencijal, konstruiran je graf ovisnosti potencijala o pF-vrijednosti koncentracija i metodom dodatka standarda matematičkim modelom određena koncentracija. Na temelju eksperimentalnih podataka doneseni su određeni zaključci. Najmanje odstupanje od očekivane koncentracije ispitivanih otopina zabilježeno je u otopini koncentracije 1,0×10 -2 mol L -1 , dok je najveće odstupanje zabilježeno u otopini koncentracije 1,0×10 -3 mol L -1 . Koncentracija otopine 1×10 -5 mol L - 1 je bila nešto malo viša u odnosu na očekivanu vrijednost kroz sva mjerenja. U nastavku eksperimenta uočeno je kako se prvotno izmjerene koncentracije previše ne mijenjaju, pri tome blago rastu ili padaju ali variraju oko početno izmjerenih vrijednosti. Iz grafičkog prikaza ovisnosti pF vrijednosti o danima mjerenja, kao i iz ovisnosti nagiba o danima mjerenja zaključeno je kako se koncentracije, iako u pojedinačnim mjerenjima blago rastu ili padaju, u konačnici ipak ne mijenjaju drastično što ukazuju i navedeni grafički prikazi iz kojih se vidi da su rezultati smješteni uglavnom linearno. Obzirom na to da se ni pri jednoj koncentraciji ne uočava kontinuirani pad vrijednosti kroz cijeli period mjerenja, zaključuje se da u ovom eksperimentu staklo ne utječe na koncentraciju fluorida.Glass is one of the most important materials in everyday life, in which it appears everywhere, and the reason it is used so often is its chemical stability. It is chemically stable due to its amorphous structure, i.e. the absence of a regular arrangement of atoms. Although glass is resistant to many chemicals, it is not universally inert. The task of this thesis was to store different concentrations of a standard solution of sodium fluoride in several glass bottles for a certain period of time, to determine whether the storage of these solutions in glass affects the change in fluoride concentration, or whether the solution (fluoride) interacts with the glass. In the experiment, sodium fluoride solutions were prepared in the concentration range of 1,0×10 -6 to 1,0×10 -2 mol L -1 . The potential was measured with the working solutions in each measurement, a graph of the dependence of the potential on the pF-value of the concentrations was constructed, and the concentration was determined using the standard addition method using a mathematical model. Based on the experimental data, certain conclusions were drawn. The smallest deviation from the expected concentration of the tested solutions was recorded in a solution with a concentration of 1,0×10 -2 mol L -1 , while the largest deviation was recorded in a solution with a concentration of 1,0×10 -3 mol L -1 . The concentration of the solution 1,0×10 -5 mol L -1 was slightly higher compared to the expected value throughout all measurements. In the continuation of the experiment, it was observed that the initially measured concentrations do not change too much, while they rise or fall slightly, but vary around the initially measured values. From the graphical presentation of the dependence of the pF value on the days of measurement, as well as from the dependence of the slope on the days of measurement, it was concluded that the concentrations, although they slightly increase or decrease in individual measurements, ultimately do not change drastically, as indicated by the above graphical representations, which show that the results are arranged mostly linearly. Given that no continuous decrease in values is observed at any concentration throughout the entire measurement period, it is concluded that in this experiment the glass does not affect the fluoride concentration
Statistical analysis of total water hardness data of the Jadro river : diploma thesis
No full textU diplomskom radu izvršena je statistička analiza podataka o ukupnoj tvrdoći vode koristeći različite statističke metode. Cilj ovog diplomskog rada je primjenom različitih statističkih metoda analizirati podatke o ukupnoj tvrdoći vode na pojedinim lokacijama u gradu Splitu kao i na samom izvorištu rijeke Jadro. Na temelju prikupljenih podataka o ukupnoj tvrdoći vode na različitim lokacijama u području Splita te na izvoru rijeke Jadro, podaci su obrađeni pomoću deskriptivne statistike kako bi se dobio uvid u osnovne karakteristike uzoraka, poput srednje vrijednosti, standardne devijacije, raspona i drugih relevantnih statističkih parametara. Daljnja analiza uključivala je primjenu inferencijalne statistike s ciljem testiranja hipoteza i donošenja zaključaka o populaciji iz koje su uzorci uzeti. Korištene metode uključivale su T - test i F - test radi utvrđivanja značajnosti razlika i povezanosti među različitim skupinama podataka. Ovim istraživanjem istaknuta je važnost statističke obrade podataka u razumijevanju i interpretaciji ne samo mjerenja tvrdoće vode, već i brojnih drugih okolnosti iz svakodnevnog života.In this thesis, a statistical analysis of data on total water hardness was conducted using various statistical methods. The aim of this thesis is to analyze data on total water hardness at specific locations in the city of Split as well as at the Jadro River source using different statistical methods. Based on the collected data on total water hardness at different locations in the Split area and at the Jadro River source, the data were processed using descriptive statistics to gain insight into the basic characteristics of the samples, such as mean, standard deviation, range, and other relevant statistical parameters. Further analysis included the application of inferential statistics to test hypotheses and draw conclusions about the population from which the samples were taken. The methods used included the T - test and F - test to determine the significance of differences and relationships between different data groups. This research highlighted the importance of statistical data processing in understanding and interpreting not only measurements of water hardness but also numerous other circumstances from everyday life
Removal of Tartrazine Yellow dye from aqueous solution by electrocoagulation : diploma thesis
No full textU radu je promatran je utjecaj gustoće struje (0.008, 0.016 ili 0.024 A/cm 2 ) na učinkovitost uklanjanja Tartrazine Yellow (TY) boje. Vrijeme elektrokoagulacijskog (EK) procesa je variralo u granicama od 10 do 50 min, a početna pH vrijednost onečišćene otopine od 3.0 do 7.0. Tijekom EK procesa dolazi do promjene pH, temperature, električne provodnosti te koncentracije TY boje. Dobiveni rezultati ukazuju na veliku učinkovitost uklanjanja TY boje, koja svih eksperimentalnih uvjeta raste i postiže konstantnu vrijednost. Maksimalna učinkovitost uklanjanja TY boje od 99.39 % postignuta je nakon 37 minuta pri i = 0.024 A/cm 2 i pH vrijednosti 3.0. Tijekom EK procesa sagledavana je potrošnja anodnog materijala koja se povećava s porastom gustoće struje. Izgled anoda nakon provedenog procesa ukazuje na opći oblik korozijskog napada čija intenzivnost ovisi o primijenjenoj struji. Operativni troškova procesa ovise o eksperimentalnim uvjetima te je uočeno da se povećavaju s porastom gustoće struje, a opadaju porastom podešene početne pH vrijednosti TY otopine.In this paper, the current density (0.008, 0.016 or 0.024 A/cm 2 ) on the efficiency of Tartrazine Yellow (TY) dye removal was investigated. The duration of the electrocoagulation (EC) process varied from 10 to 50 minutes and the initial pH of the contaminated solution from 3.0 to 7.0. During the EC process, the pH, temperature, electrical conductivity, and concentration of the TY dye changed. The results show a high efficiency in removing TY dye, which increases and reaches a constant value under all experimental conditions. The maximum TY dye removal efficiency of 99.39% was achieved after 37 minutes at i = 0.024 A/cm 2 and a pH of 3.0. During the EC process, the consumption of the anode material was observed to increase with the increase in current density. The appearance of the anodes after the process indicates a general form of corrosion attack, the intensity of which depends on the applied current. The operating costs of the process depend on the experimental conditions and were observed to increase with the increase in current density and decrease with the increase in the adjusted initial pH of the TY solution
Analysis and design of a teaching aid for vibration theory
No full textVibracije su neizostavni dio industrije, a u današnje vrijeme kada sve ubrzano napreduje bitno je znati rješavati probleme koji se stavljaju pred inženjere. Kako bi problem vibracija bio što lakše rješiv bitno je od početka razumjeti kako vibracije nastaju i koji su postupci rješavanja istih.
Mehaničke vibracije su periodična ili kvaziperiodična gibanja mehaničkih sustava koja mogu nastati uslijed vanjskih uzbuda ili unutarnjih dinamičkih svojstava sustava. Isaac Newton svojim je drugim zakonom postavio temeljnu dinamiku čitave klasične mehanike, uključujući i analizu vibracija. Jean Baptiste le Rond d'Alembert tu je osnovu produbio razvojem d'Alembertova načela i matematičkih metoda za rješavanje gibanja niza praktičnih vibracijskih sustava, osobito kontinuiranih. Zajedno, njihova razmatranja omogućuju razradu općih jednadžbi za proučavanje, kontrolu i prigušenje mehaničkih vibracija te čine temelj suvremene teorije oscilacija.
U ovom radu dan je pregled triju koncepata nastavnog pomagala za razmatranje i proučavanje u nastavi koji će studentima olakšati shvaćanje vibracija. Svaki koncept se razlikuje po osnovnim dijelovima uređaja kao što su linearna vodilica, vozičak i uteg (masa). Nakon pregleda svih koncepata odabran je najbolji koncept koji je i konstrukcijski razrađen. Odabrani koncept razrađen je analitički te parametriziran i programiran u Matlabu.Vibrations are an unavoidable part of today's industry, where everything is developing at fast pace. As engineers, it's important to be able to deal with presented challenges. For a better understanding of vibration problems it's crucial to understand how they occur and what necessary steps are needed to solve them.
Mechanical vibrations are periodic or quasi-periodic movements of mechanical systems that can appear due to external excitations or internal dynamic properties of the system. Isaac Newton's second law laid the foundation for the dynamics of classical mechanics, including vibration analysis. Jean-Baptiste le Rond d'Alembert development d'Alembert's principle and mathematical methods for solving the motion of various practical vibration systems, especially continuous vibration systems. Together, their work enabled the development of general equations for studying, controlling, and damping mechanical vibrations, which form the foundation of modern oscillation theory.
In this paper, an overview of three teaching approaches to vibration is given, which will make students' understanding of vibrations easier. Each concept differs from the others based on primary components such as linear guide, carriage and mass. After reviewing all concepts, the best one was chosen and structurally elaborated. The chosen concept is explored analytically, parametrized, and programmed in MATLAB
Comparison of welding technology of Y-25 longitudinal beams
No full textCilj ovog rada je istražiti razlike prilikom zavarivanja uzdužnih greda Y-25 poluautomatskim i
robotskim MAG postupkom zavarivanja. Uzdužne grede se koriste za izgradnju postolja Y25
koja su predviđena za daljnju montažu teretnih vagona.
U teorijskom dijelu rada istraženo je koji se čelici koriste prilikom zavarivanja uzdužnih greda
Y-25, kakva je njihova zavarljivost te na što treba obratiti pozornost. Također je opisano što
predstavljaju uzdužne grede Y-25. Osim istraživanja čelika, opisan je način rada s
poluautomatski i robotskim MAG postupkom zavarivanja i njihovi parametri.
U eksperimentalnom dijelu prikazani su rezultati dobiveni prilikom zavarivanja uzdužnih greda
na okretnim postoljima robotskim MAG-om te usporedba kvalitete zavara s poluautomatskim
postupkom MAG zavarivanja.The aim of this research paper is to explore differences between semi-automatic and robotic
MAG , whilst welding longitudinal beams Y-25. Longitudinal beams are used for construction
of Y25 boogies, which are further intended for assembly of freight cars.
In theoretical part of this research paper, it is explored what steel is is used for welding
longitudinal beam Y-25, steels weldability and where do we have to focus our attention in doing
so. Also it is described what longitudinal beam represent and what they are. In addition to steel
research, the way of working with semi-automatic and robotic MAG welding process are
described as well as their parameters.
In the experimental part of the research paper, the results obtained during the welding of
longitudinal beams on turntables with robotic MAG welding are compared to results of manual
MAG welding