Plastično oblikovanje lima nestišljivim fluidom

The plastic forming of sheet metal with fluid pressure has most application at the modern producing of special elements and element of widespread use. Higher relations of drawing ratio are reached by the application of this technology and it is decreased the number of necessary operations and tools as well as the decreasing of costs to product unit. The quality of produced products is considerable better than clasic methods therefore there are satisfactory tribological conditions of plastic forming. Therefore there is considerable application increasing of this technology at the technological developed countries.Plastično oblikovanje pomoću nestišljivog fluida ima sve veću primjenu u modernoj proizvodnji specijalnih elemenata i elemenata široke potrošnje. Primjenom ove tehnologije postižu se veći odnosi izvlačenja, smanjuje se broj potrebnih operacija i alata, te se smanjuju troškovi izrade po jedinici proizvoda. Kvaliteta dobivenih proizvoda je znatno bolja u odnosu na klasične metode jer su bolji tribološki uvjeti plastičnog oblikovanja. Zbog toga je značajan porast primjene ove tehnologije u tehnološki razvijenim zemljama

A Zincian Chrome-Spinel from the Cr-Ba-Fe-Cu-Zn Deposit near Busovaca (Bosnia and Herzegovina)

The metamorphic complex of the Busovaca area is mostly composed of Upper Silurian-Lower Devonian metapelites, metapsammites and metarhyolites formed under low grade metamorphism at 350° to 450°C and 3 to 5 kbars. The ore minerals of the Busovaca deposit are: magnetite (with relics of zincian chrome-spinel), rimmed by ferrichromite, and pyrite, chalcopyrite, enargite, bornite and siegenite. The gangue minerals are: siderite, quartz, albite, hyalophane, muscovite, chromian-chlorite and manganoan ankerite. Proton microprobe analyses (PIXE) were made of samples A (core Ac of the slightly altered chrome-spinel), B (strongly altered chrome-spinel with Bc-core, Bfc-ferrichromite zones, Br-magnetite rim) and C (cryptically zoned magnetite with Cc-core and Cr-magnetite rim). The results are recalculated in formulae, and presented on separate diagrams. The optical investigations, microprobe analyses, beam-scan photographs, diffusion rates of Mg, Al, Zn, Cr, and Mn, and diagrams, allow the following conclusions to be made: (1) magmatic origin of the primary chrome-spinel, (2) the emplacement of the Zn was prior to the alteration under very low f02, most probably synchronous with the sulphide mineralization; (3) the alteration process took place in two phases: (a) the early stage volume-for-volume replacement and formation of the ferrichromite and magnetite zones, (b) the late stage characterized by decolourization and/or resorption, and/or dissolution of the core (patches, specks, “atoll structure”); (4) released Al, Cr, Mn, and Zn have been taken up by silicate, carbonate and oxide minerals forming chromian-chlorite, manganoan ankerite or contaminated siderite and pyrite; (5) the diffusion rates among Al, Zn, Cr, and Mn during different stages of the alteration have the following sequence: Al - Zn - Cr - Mn; (6) the optically unzoned magnetite crystals or aggregates originated in chrome-spinel; (7) the mineral assemblage of the Busovaca deposit co-exists with the surrounding metamorphic complex belonging to the greenschist facies

Lanthanide Geochemistry and Fluid Inclusion Peculiarities of the Fluorite from the Barite Deposits South of Kresevo (Bosnia and Herzegovina)

Strata-bound barite deposits occur in Devonian dolomites, situated in the Mid-Bosnian Palaeozoic Schist Mountains. These contain barite as the main ore mineral (5.9 wt% SrSO4 on average and d34S= +8.3‰) which comprises 90-99 wt% of the bulk ores. The subordinate components are calcite, fluorite, Hg-Sb-tetrahedrite, pyrite and quartz. Analysis of REE by INAA revealed an extremely low content of lanthanides (1.584 ppm), negative Eu anomalies (Eu3+/Eu+ = 0.7398), and (Tb)N/(La)N = 6.2 indicating late-stage mineralization. Primary fluid inclusions show a uniform number of infilling phases (L+V+S), and persistent volume ratio. This indicates homogeneity of the hydrothermal ore-forming fluids and an absence of boiling phenomena at the time of fluorite formation. Th is between 200° and 310°C, with a distinctive maximum at 250°C. Tfm -20.3°C predominates but careful examinations of the early melting behaviour of the inclusions warrants the existence of Tfm -51°C, and the presence of CaCl2. High salinity between 25 and 26 wt% eq. NaCl was determined from the hydrohalite melting temperature (Tmh). Some additional daughter minerals are also present. Fluorite, barite and calcite formed from the high saline waters probably originated by mixing of heated hydrothermal fluids with the highly evolved post-Variscan Upper Permian formation waters. This is supported by the study of the isotopic composition of the carbon, oxygen and sulphur of the paragenetic carbonates and sulphides

Use of pyrophyllite to reduce heavy metals mobility in a soil environment

This study revealed the effects of pyrophyllite ore materials on heavy metals mobility in soil plots located near the steel mill in Zenica (Bosnia and Herzegovina). The experiment was set up in a randomized block design with four pyrophyllite treatment rates i.e. 0, 200, 400 and 600 kg ha-1 in three replications. Analyses of the heavy metals (Cu, Zn, Mn, Ni, Cr, Pb, Cd) in soil and plant samples were performed using atomic absorption spectrophotometry. Pyrophyllite addition in soil was found to reduce the availability of all tested heavy metals in the studied soil. The pyrophyllite addition at a rate of 200 kg ha-1 reduced Mn, Cu and Zn available forms in soil by 11.1, 20.4 and 11.2%, respectively, compared with control. The pyrophyllite addition at higher rates i.e. 400 and 600 kg ha-1 had an even higher impact on the decrease in Mn and Zn mobility in studied soil in comparison with 200 kg ha-1 . Additionally, these pyrophyllite rates have the ability to reduce Ni mobility in studied soil. The study also found a positive effect of all pyrophyllite treatments to reduce heavy metals accumulation in the leaves of potato grown on the studied soil. In sum, the results of this study indicate that pyrophyllite treatment could be an effective technique for improving the environmental quality of soils and alleviating the hazards of heavy metals to plants. However, further studies are necessary to confirm or denied this hypothesis

Plastično oblikovanje lima nestišljivim fluidom

The plastic forming of sheet metal with fluid pressure has most application at the modern producing of special elements and element of widespread use. Higher relations of drawing ratio are reached by the application of this technology and it is decreased the number of necessary operations and tools as well as the decreasing of costs to product unit. The quality of produced products is considerable better than clasic methods therefore there are satisfactory tribological conditions of plastic forming. Therefore there is considerable application increasing of this technology at the technological developed countries.Plastično oblikovanje pomoću nestišljivog fluida ima sve veću primjenu u modernoj proizvodnji specijalnih elemenata i elemenata široke potrošnje. Primjenom ove tehnologije postižu se veći odnosi izvlačenja, smanjuje se broj potrebnih operacija i alata, te se smanjuju troškovi izrade po jedinici proizvoda. Kvaliteta dobivenih proizvoda je znatno bolja u odnosu na klasične metode jer su bolji tribološki uvjeti plastičnog oblikovanja. Zbog toga je značajan porast primjene ove tehnologije u tehnološki razvijenim zemljama

Strontium Dependence of the Lattice Constants of Barites from the Kresevo Area in Central Bosnia (Bosnia and Herzegovina)

The lattice constants of a synthetic BaSO4 and fourteen natural barite samples from the Kresevo area (Central Bosnia) were determined by X-ray powder diffraction. The natural samples contained from 0.3-17.6 mole % SrSO4, and negligible concentrations of Ca and Pb (<0.03 and 0.02 wt. %, respectively), thus representing almost pure (Ba,Sr)SO4 solid solutions. The diffraction lines of most natural samples were broadened in relation to those of synthetic BaSO4. This results from obvious compositional heterogeneity, e.g. the heterogeneous distribution of strontium, as is clearly observed from Sr variation patterns across a surface of the barite obtained by proton microprobe analysis. Nevertheless, the present values of unit-cell parameters are in agreement with those of synthetic (Ba,Sr)SO4 solid solutions documented in the literature. It has been proven that the interplanar spacing d004 may be used for determination of the Sr content of natural barites; the absolute error varies from ±0.3 mole % SrSO4 (for homogeneous samples having the diffraction line 004 clearly resolved in spectral doublet components) up to ±0.5 mole % SrSO4 (for the samples with compositional heterogeneity having a broadened and relative poorly defined diffraction line 004)

Primjena neuronske mreže kod procjene površinske hrapavosti nakon završne obrade valjanjem

In order to increase productivity, machining times and market competitiveness of machining production systems, it is important to continuously develop existing technological solutions. This article describes the usage of the neural network for the prediction of surface roughness after the roller burnishing. Since the observed problem is multidimensional with several input parameters and one output parameter and since nonlinearity and complexity of parameter correlation, there was used the backpropagation neural network algorithm. Empirical and experimental values of input and output parameters were used as initial values for the learning of the neural network. Developed neural network model with its results can be used for easier implementation of further roller burnishing process plans.Ovaj rad opisuje primjenu umjetne neuronske mreže za predviđanje hrapavosti površine obratka nakon završne obrade valjanjem. S obzirom da se radi o višedimenzionalnom problemu sa nekoliko ulaznih te jednim izlaznim parametrom te da je njihova međusobna funkcijska povezanost vrlo kompleksna, nelinearna i na kraju i nepoznata, korištena je višeslojna neuronska mreža sa primjenom algoritma “širenja unatrag”. Naime, iskustvene i eksperimentalne vrijednosti, korištene kao ulazni i izlazni parametar u svrhu učenja neuronske mreže, poslužile su kao dobra polazišna točka sustavu umjetne inteligencije za razradu općenitog modela koji se kasnije može koristiti u svrhu izgradnje nekih viših ekspertnih sustava lako upotrebljivih prilikom izrade tehnologije za završnu obradu površine valjanjem

Scripta in honorem Igor Fisković: zbornik povodom sedamdesetog rođendana

The International Research Centre for Late Antiquity and the Middle Ages prepared a Festschrift in honour of one of its founders, Igor Fisković on the occassion of his 70th birthday. The Festschrift&nbsp; includes works addressing the periods that Igor Fisković has dealt with most, thus reflecting the diversity of his interests, ranging from Late Antiquity to contemporary art, with key emphasis on the Late Middle Ages and early modernity. Due to the diversity and the broad period of time the texts are covering, they have been arranged more or less chronologically. The works focus mainly on the Late Middle Ages and the early modern period, Fisković’s forte and the topic of some of his best writings. There are also several texts addressing the baroque period, which was not one of the honouree’s interests, but they were written by some of his closest friends and members of the generation of his former students who have had prestigious careers. (from the Foreword)Zbornik je pripredio Međunarodni istraživački centar za kasnu antiku i srednji vijek povodom sedamdesetog rođendana jednog od svojih osnivača Igora Fiskovića. Zbornik obuhvaća radove koje pokrivaju razdoblja kojima se Igor Fisković ponajviše bavio, reflektirajući raznolikost njegovih interesa, od početne kasne antike i suvremene umjetnosti, do ključnoga naglaska na kasnom srednjem vijeku i početku modernog doba. Zbog te raznolikosti i širokog vremenskog razdoblja koje pokrivaju, radovi su poredani manje-više kronološki. Ističe se brojem radova upravo kasnosrednjovjekovno doba i početci modernoga, forte u kojem je Igor Fisković dao svoje ponajbolje radove. Uz njih je i više priloga koji pokrivaju razdoblje baroka, kojim se slavljenik nije bavio, no koji su iz pera njegovih najbliskijih prijatelja i one generacije njegovih bivših studenata koji su danas ostvarili ugledne karijere. (iz Predgovora