Metallization degree of pre-reduced chromite was determined using two methods. The chromite samples were reduced in the solid state by methane-hydrogen gas mixtures. First method was image analysis ...of micrographs obtained by scanning electron microscope where heavier metallic phases appeared as bright white areas which were relatively easy to segment using a thresholding algorithm. The second technique was Rietveld analysis of X-ray powder diffraction pattern which fitted a calculated profile onto a measured X-ray diffraction pattern to gain information about phase quantities. Rietveld refinement and phase composition analysis was performed with PANalytical?s X?Pert HighScore Plus software from the XRPD (X-ray powder diffraction) data. Both techniques were in good agreement. Metallization degrees for the investigated samples ranged from 15 to 65 % depending on the extent of reduction which was a function of time, reduction temperature, and methane content of the gas mixture. These results were promising and indicate that either image analysis or X-ray Rietveld analysis can be used as a relatively fast method to determine the degree of metallization of pre-reduced samples in comparison to the slow and tedious chemical analysis.
In this study, copper alloy matrix composites reinforced with tungsten carbide (WC) particles with the addition of different Ni contents (0, 3, 5, 7, and 10 wt.%) were prepared by the spontaneous ...infiltration process. Image analysis was used to quantify the microstructural parameters, such as the particle size and distribution, area fraction, binder mean free path, and pore size. The effect of Ni addition on the microstructure, density and hardness are discussed. The results show that a small addition of Ni improves the densification of the infiltrated composites. The highest density value of 11.84 g/cm3 with a hardness of 327 HV was obtained for the infiltrated composite with the addition of 3 wt.% of Ni. The quantitative analysis results are in good agreement with the microstructure properties and hardness results.
nema
Centar izvrsnosti za računalni vid Lončarić, Sven; Bogdan, Stjepan; Gajski, Dubravko ...
Annual of the Croatian Academy of Engineering,
06/2022, Letnik:
2021, Številka:
1
Journal Article
Odprti dostop
Centar izvrsnosti za računalni vid na Fakultetu elektrotehnike i računarstva (FER) osnovan je 2012. godine sa ciljem okupljanja relevantnih istraživača s FER-a i s drugih sastavnica Sveučilišta. U ...osnivanju Centra sudjelovalo je sedam sastavnica Sveučilišta u Zagrebu. Ciljevi Centra su jačanje međunarodne vidljivosti Sveučilišta u Zagrebu u području računalnog vida, stvaranje kritične mase istraživača za zajednički nastup u većim znanstvenoistraživačkim i razvojnim projektima, poboljšanje kvalitete doktorskih istraživanja u području računalnog vida i poticanje zajedničkog nastupa prema gospodarstvu radi suradnje i transfera tehnologije. U radu je predstavljena motivacija za osnivanje Centra te znanstvene i stručne aktivnosti članova Centra.
Provider: - Institution: - Data provided by Europeana Collections- Building materials come into the focus of interest at the time when waste,
industrial or municipal, is becoming increasingly ...important as a potential
raw material. Probable cause for that is the base of building materials-
cement which contains numerous waste materials originating from the
ingredients or the fuel used for its production. On the one side, the primary
application area of building materials has been constantly expanding, but
beside these materials, the alternative materials are also taking their
place. Modification of conventional building materials is commonly realized
using some of the secondary raw materials from various industrial processes.
Generally, building materials and their products are important recipients of
waste as long as they can provide complete immobilization without degradation
of their basic properties. Nowadays, most researches in the world are devoted
to using ashes from power plants and other large incinerators in order to
obtain high-quality building material with wide range of applications. By
following the similar concept, possibility of using secondary sulfur as an
alternative component of concrete was analized in this thesis. Waste sulfur
is often neglected despite the large amount of globally produced secondary
sulfur which possibly exceeds the amount of ash to whom a great importance is
given. Technological revolution has brought a reversible process to the
natural process of sulfur removing from the atmosphere, that is sulfur
restoring by processing of crude oil, natural gas and ores. The by-products
thereby obtained, sulfur and sulfuric acid, present serious environmental
problem. Therefore, it was necessary to consider alternative ways of sulfur
and sulfuric acid valorization in the real process (large scale). In this
case, the solutions can be found in application of these types of secondary
sulfur for fertilizers production, immobilization of waste materials by
conversion into insoluble compounds, and as an additive in building
materials. In the research presented in this thesis, the use of secondary
sulfur as binding agent in concrete for wide application possibilities was
analysed. The starting point was the fact that sulfur is known as a binder
and that it can quite possibly be used as a binding agent in building
materials. The initial studies were directed towards modification of sulfur
for the application in sulfur concrete. The next step was the analysis of
technology ie. process of sulfur concrete obtaining in order to optimize the
technological parameters for producing high-quality material. This was
followed by the researches related to the examination of sulfur concrete
properties, as well as testing the new material quality during the
exploitation, which was more important. The fact is that the influence of
various environmental factors causes a certain degree of destruction and
therefore degradation of the basic properties of all materials, including the
building materials. In case of metals, these processes are well-known as
corrosion which can be generally attributed to all inorganic materials. In
case of organic materials, the mentioned process is known as material aging
under the influence of environmental factors. The other fact is that the
processes of accellerated corrosion or aging are caused by high atmospheric,
water, and soil pollution, so the investigation of the newly obtained
material- sulfur concrete was directed towards the analysis of its behavior
in the presence of the induced destruction agent. There are two key elements
during the application of this methodology. The first one is a selection of
the induced destruction gent, while the other one is a selection of methods,
that means methodologies for monitoring and quantifying changes that occur
under the influence of the certain agent. When choosing the induced
destruction agent for inorganic materials, the decisive factor can be
aggressiveness of the substance, whereby strong acids or bases are usually
selected. In the scope of this research, hydrochloric acid, sulfuric acid,
and sodium chloride were used in screening experiment which was realized with
the aim to choose the induced destruction agent. In the second screening
experiment, which was performed using chosen induced destruction agent-
hydrochloric acid, the time required for the complete degradation of the
reference material, Portland cement concrete was investigated. The results
showed that the reference material lost its properties after 21 days of
treatment, while sulfur concrete kept its properties even after a year of
treatment. The filler and the treatment time were also determined through
screening experiments. In this way, after screening experiments, the
material, the induced destruction agent, and the treatment time were
precisely defined. In examining the materials properties, as well as in
selecting methods for quantifying their changes, classical aspect was not
applied. The idea was to implement a number of destructive and nondestructive
methods and correlate the material properties with the structure. The
structure of the obtained material was analyzed by the methodology of
quantification of visual information whereby the images obtained by optical
and scanning electron microscopes were used. It means that properties of the
material structure were analyzed by different resolutions. For testing the
material behavior under the influence of the induced destruction agent, the
ultrasonic method, which offers defining the homogenity changes of the
samples during the treatment time, and thermovision for examining the thermal
properties were applied. Mechanical testing results showed that sulfur
concrete had possessed satisfactory properties and kept them after six months
of treatment by the induced destruction agent. Based on the ultrasonic
examination, it was found that significant qualitative changes in the
structure of sulfur concrete occurred after a certain period, whereby the
most intensive homogenity change happened during 21 days of the agent
influence, and after that period, its effect weakened. This indicated the
rearrangement of the constituents in the material. Scanning electron
microscopy showed a rearrangement of the structure during the treatment.
Energy dispersive X-ray analysis (EDS) was also performed. The mapping showed
the concentration of sulfur in some locations. Based on the SEM analysis, it
was concluded that sulfur had a major role in rearrangement that was
occurring as a consequence of the agent influence. The thermovision analysis
results pointed out significant structural differences among the sulfur
concrete samples treated by the agent during the different time periods.
Also, the same analysis showed noticeable differences in thermal properties
between sulfur concrete and Portland cement concrete samples owing to the
structural changes during the exposure to the agent. Based on the obtained
results, working models for defining correlations between mechanical and
structural properties of the tested materials were developed. As an additon
to the study of possible secondary sulfur application in production of
building materials, synthesis of sulfur modified asphalt and its
characterization by standard methods were presented. The tests showed
advantages of sulfur modified asphalt over the conventional asphalt. Part of
these results was published in relevant international journals.- Građevinski materijali dolaze u fokus interesovanja u vreme kada otpad, bilo
industrijski, bilo komunalni, dobija na značaju kao potencijalna sirovina.
Verovatan razlog za to je osnova građevinskog materijala-cement, koji u svom
sastavu ima i veliki broj uslovno otpadnih materijala koji mogu da vode
poreklo od sastojaka ili od energenata koji se koriste za njegovu
proizvodnju. S jedne strane, primarna primena građevinskih materijala sve se
više širi, ali pored njih i alternativni materijali dobijaju svoje mesto.
Modifikacija konvencionalnih građevinskih materijala uglavnom se vrši
korišćenjem nekih od sekundarnih sirovina iz različitih industrijskih
procesa. Generalno gledajući, građevinski materijali i njihovi proizvodi
značajni su akceptori otpadnih materija ukoliko mogu u potpunosti da izvrše
njihovu imobilizaciju, pri čemu mora biti ispunjen uslov da ne dolazi do
degradacije osnovnih svojstava samog materijala. Danas se najveći broj
istraživanja u svetu odnosi na korišćenje pepela iz termoelektrana i ostalih
velikih insineratora u cilju dobijanja kvalitetnog građevinskog materijala
široke primene. Prateći sličnu koncepciju, u ovom radu prikazana je i
analizirana mogućnost korišćenja sekundarnog sumpora kao alternativnog
sastojka betona. Sumpor cesto predstavlja zapostavljen otpad, iako je veliko
pitanje da li količina proizvedenog sekundarnog sumpora na svetskom nivou
premašuje količinu pepela kome se pridaje veliki značaj. Zahvaljujući
tehnološkoj revoluciji, došlo je do vraćanja sumpora u atmosferu preradom
nafte, prirodnog gasa i II ruda, što predstavlja reverzibilan proces
prirodnom uklanjanju sumpora iz atmosfere. Tako se kao nusproizvodi dobijaju
sumpor i sumporna kiselina koji danas predstavljaju ozbiljan ekološki
problem. Zbog toga je bilo neophodno razmatrati alternativne načine
valorizacije sumpora i sumporne kiseline u realnom procesu (large scale). U
tom slučaju, rešenja se mogu naći u korišćenju pomenutih vrsta sekundarnog
sumpora u proizvodnji đubriva, imobilizaciji otpadnih materijala prevođenjem
u nerastvorna jedinjenja i kao dodatak odgovarajućim građevinskim
materijalima. U prikazanim istraživanjima analiziran je aspekt korišćenja
sekundarnog sumpora kao veziva u betonima čije su mogućnosti primene široke.
Polazna osnova bila je činjenica da je sumpor poznat kao vezivna supstanca i
da ga je sasvim moguće koristiti kao vezivno sredstvo i u građevinskim
materijalima. Prva istraživanja bila su usmerena ka modifikaciji sumpor
Rana prognoza uroda jabuka i krušaka napravljena na temelju lipanjskog pregleda voćnjaka od iznimne je važnosti za organizaciju berbe, planiranje rashladnih prostora, izbora voća za duže skladištenje ...te postavljanje prodajnih cijena i mogućnosti prodaje na domaćim odnosno stranim tržištima. U radu je predstavljen suvremen pristup vizualizacije rodnog volumena stabala pomoću digitalnog fotoaparata te obrada digitalnih slika za potrebe računanja očekivanog uroda za vrijeme berbe. Predstavljena metoda u praktične namjene koristi se u Sloveniji od 2004. godini, a bila je uspješno testirana u više susjednih zemalja pa tako i u Hrvatskoj.
Ovo istraživanje pokušava analizirati posljedice gubitka paketa u prijenosu komunikacijskim kanalom u vidu pogrešaka na slici. Greške se simuliraju korištenjem tri najčešća tipa grešaka u ...komunikacijskom kanalu uz korištenje dva tipa entropijskog kodiranja. Na dobivenim, oštećenim, slikama provodi se objektivna analiza slike te se rezultati prikazuju u tabličnom obliku.
Provider: - Institution: University of Zagreb. School of Dental Medicine. Department of Oral Surgery. - Data provided by Europeana Collections- Svrha je istraživanja bila testirati mogućnosti uporabe ...specijaliziranoga računalnog programa za kompjutoriziranu analizu digitalnih RVG snimaka za pronalaženje regije interesa na sukcesivnim snimkama i za mjerenje srednjih vrijednosti zasjenjenja regije interesa oko implantata. Za tu se svrhu obradilo 180 digitalnih rendgenskih snimaka kod 60 ispitanika podijeljenih u dvije grupe po 30 ispitanika, kojima je gubitak jednog zuba u premolarnoj regiji gornje čeljusti nadomješten ugradnjom dentalnog implantata Nobel Replace Tapered Groovy (Nobel Biocare, Gothenburg, Sweden). Prvu skupinu ispitanika čine pacijenti kojima je implantat ugrađen imedijatno, odnosno neposredno nakon ekstrakcije zuba, dok su drugoj skupini ispitanika, koju također čini 30 pacijenata, implantati ugrađeni u formiranu alveolnu kost standardnom odgođenom tehnikom. Svim je ispitanicima 4-6 mjeseci nakon ugradnje implantata postavljena metal keramička krunica. Prije postave krunice implantati nisu bili funkcionalno opterećeni. Računalnim su se programom mjerile digitalne snimke svakog ispitanika regije interesa (veličine 0,5 mm x 0,5 mm i veličine 0,5 mm x 1,5 mm) na sedam mjesta oko implantata tri puta (nakon ugradnje, 4-6 mjeseci nakon ugradnje, odnosno postavljanja suprastrukture i nakon godinu dana). Za provjeru računalnog programa rezultati zasjenjenja su se uspoređivali s Osstell testom i kliničkim parametrima.
Promjene razine zasjenjenja su se između skupina ispitanika pokazale statistički značajnima u smislu veće promjene zasjenjenja kod imedijatno ugrađenih implantata u odnosu na odgođenu implantaciju tijekom praćenja od godinu dana. Promjene razine zasjenjenja su korelirale s vrijednostima Osstell testa i parodontološkim indeksima. Pokazalo se da je za precizniji prikaz zasjenjenja kosti preporučljivo koristi veću regiju interesa (0,5 mm x 1,5 mm) u odnosu na manju (0,5 mm x 0,5 mm).
Računalni se program pokazao pouzdani i objektivni parametar za praćenje promjena razine zasjenjenja u dentalnoj implantologiji.- The aim of this research was to test the possibility of the use of a specialized software for the analysis of digital RVG images to find the areas of interest on the successive images, and the measurement of average values of shading areas of interest around the implants.
Materials and methods: One hundred and eighty digital radiographs were processed of 60 patients, divided in 2 groups of 30, whose lost tooth in the maxillary premolar region was replaced with a NobelReplace™ Tapered Groovy (Nobel Biocare, Gothenburg, Sweden) dental implant. The first group consisted of patients who received immediate implant placements following tooth extraction, while the other group of patients received their implant placements in healed sites. All patients received metal ceramic crowns four to six months after the implant placement. The implants were not exposed to functional loading prior to crown placement. The computer program was used to measure digital images of each patient's area of interest (sizes 0.5 mm × 0.5 mm and 0.5 mm × 1.5 mm) of seven areas around the implant at three time intervals (after the implant placement, 4-6 months after the placement of implant suprastructure and after one year). To verify the computer program evaluation, the results of shading areas were compared with Ossell test and clinical parameters.
Results: Loss of a single implant has not been described. The results showed a significant increase of shading six months after the implant placement, which corresponded to the osseointegration, while a year after the implant placement a mild decrease in shading was observed, compared to the second measurement, which can be attributed to the functional bone remodelling after functional loading. Changes in the levels of shading monitored for one year between the groups of patients were statistically significant; greater changes in shading were observed in patients who received immediate implant placements following tooth extraction, compared to the patients with implant placements in healed sites. These changes correlated with the values of Ossell test and periodontal indices. There was no statistically significant difference related to average change in ISQ values between the immediate and
delayed groups. Statistically significant correlations between smoking habits and changes in shading, Osstell test and clinical parameters were found.
Conclusion: The computer program appeared to be a promising tool in finding the regions of interest in successive images, i.e. for measuring average values of shading of the areas of interest. Titanium implants for correction, i.e. standardization of images has proven satisfactory outcome in annulling the difference in the exposition of each image. For more precise representation of bone shading, the use of the larger area of interest (0.5 mm × 1.5 mm), compared to the smaller one (0.5 mm × 0.5 mm), is recommended.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Cilj istraživanja bio je ispitati mogućnost upotrebe metoda procesiranja i analiziranja slike za ranu prognozu uroda jabuka sorti Golden Delicious, Jonagold i Idared, cijepljenih na podlozi M9 u ...pedoklimatskim uvjetima Međimurja. Kod analize slike najbolje prognoze u prosjeku su dobivene u srednje kasne sorte Idared (-734
kg/ha), a najslabije kod sorte Golden Delicious (-4.700 kg/ha), dok je kod sorte Jonagold urod u prosjeku precijenjen za 3.266 kg/ha. U buduća istraživanja potrebno je uključiti i ostale sorte iz asortimana te prilagoditi krivulje rasta lokalnim pedoklimatskim uvjetima.
Rad se bavi procjenom razlika između gornje i donje strane OSB/3 ploča, prije svega u smislu savojnog naprezanja. OSB ploče drvni su materijal proizveden od drvnog iverja velike površine, nepravilnog ...oblika i nejednake duljine. Drvno je iverje slučajno raspoređeno te stoga nije uvijek potpuno pravilno orijentirano. Razlike u sastavu površinskih slojeva OSB ploča bitno utječu na nejednolikost svojstava ploča, posebice pri opterećenju na savijanje. Provedena mjerenja pokazala su da OSB ploče koje su pri testiranju okrenute gornjom površinom ploče prema dolje mogu podnijeti veća opterećenja na savijanje i bilježe manje deformacije od ploča koje su pri testiranju bile postavljene donjom površinom prema dolje.
Ovaj rad prikazuje postojeće standardne metode za mjerenje i određivanje udjela lomnih površina kroz drvo, nedostatke njihove primjene te usporedbu standardnih metoda s novom metodom. Novom metodom ...za određivanje udjela loma kroz drvo uklanjaju se nedostaci postojećih metoda odnosno subjektivni utjecaji ispitivača
i povećava se preciznost mjerenja. Metoda se temelji na fotografiranju lomnih površina koje se zatim obrađuju i analiziraju računalom. Rezultati pokazuju da je ova metoda objektivnija i točnija od normiranih metoda.
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