Propusnost kod projektiranja procesa izrade čeličnih cijevi

Conventional approach to pipe manufacturing process design is using capacity to satisfy maximal load for each process. In the new approach, throughput is suggested as a basic determinant aiming at finding dynamic balance among following and previous process phases. Throughput is defined by the interval of time between product exiting from the preceding process phase and its entry to the next one. Interval of time for the product delivery from the preceding phase must be less or equal as the amount of time necessary for activating the next phase. Knowing the performances of the next phase one can impact to the characteristics of the preceding phase. Throughput can be also used as a more precise way for observed process productivity measurement. Such approach is suggested and for other complex technological processes.Konvencionalni pristup projektiranju procesa izrade cijevi koristi kapacitet kako bi se zadovoljilo maksimalno opterećenje u svakom trenutku procesa. U novom se pristupu kao temeljna odrednica predlaže propusnost, koja teži iznalaženju dinamičke ravnoteže narednih i prethodnih faza procesa. Propusnost se definira međuvremenima izlaza proizvoda iz jedne faze procesa i ulaska u narednu, gdje međuvrijeme isporuke proizvoda iz promatrane faze, mora biti manje ili jednako vremenu potrebnom za aktiviranje naredne faze. Tako je moguće, poznavajući performanse narednog procesa, utjecati na karakteristike onog promatranog. Propusnost se koristi i kao precizniji način mjerenja učinkovitosti promatranog procesa. Pristup se može koristiti i za druge složene tehnološke procese

The politics of performance: transnationalism and its limits in former Yugoslav popular music, 1999–2004

This paper examines transnational relations between the Yugoslav successor states from the point of view of popular music, and demonstrates how transnational musical figures (such as Djordje Balaševi?, Mom?ilo Bajagi?-Bajaga and Ceca Ražnatovi?) are interpreted as symbolic reference points in national ethnopolitical discourse in the process of identity construction. Another symbolic function is served by Serbian turbofolk artists, who in Croatia serve as a cultural resource to distance oneself from a musical genre associated by many urban Croats with the ruralization (and Herzegovinization) of Croatian city space. In addition, value judgements associated with both Serbian and Croatian newly composed folk music provide an insight into the transnational negotiation of conflicting identities in the ex-Yugoslav context. Ultimately the paper shows how the ethnonational boundaries established by nationalizing ideologies created separate cultural spaces which themselves have been transnationalized after Yugoslavia's disintegration

Metal Bioavailability in the Sava River Water

Metals present one of the major contamination problems for freshwater systems, such as the Sava River, due to their high toxicity, persistence, and tendency to accumulate in sediment and living organisms. The comprehensive assessment of the metal bioavailability in the Sava River encompassed the analyses of dissolved and DGT-labile metal species of nine metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the river water, as well as the evaluation of the accumulation of five metals (Cd, Cu, Fe, Mn, and Zn) in three organs (liver, gills, and gastrointestinal tissue) of the bioindicator organism, fish species European chub (Squalius cephalus L.).This survey was conducted mainly during the year 2006, in two sampling campaigns, in April/May and September, as periods representative for chub spawning and post-spawning. Additionally, metal concentrations were determined in the intestinal parasites acanthocephalans, which are known for their high affinity for metal accumulation. Metallothionein concentrations were also determined in three chub organs, as a commonly applied biomarker of metal exposure. Based on the metal concentrations in the river water, the Sava River was defined as weakly contaminated and mainly comparable with unpolluted rivers, which enabled the analyses of physiological variability of metal and metallothionein concentrations in the chub organs, as well as the establishment of their constitutive levels

Throughput for steel pipes manufacturing process design

Conventional approach to pipe manufacturing process design is using capacity to satisfy maximal load for each process. In the new approach, throughput is suggested as a basic determinant aiming at finding dynamic balance among following and previous process phases. Throughput is defined by the interval of time between product exiting from the preceding process phase and its entry to the next one. Interval of time for the product delivery from the preceding phase must be less or equal as the amount of time necessary for activating the next phase. Knowing the performances of the next phase one can impact to the characteristics of the preceding phase. Throughput can be also used as a more precise way for observed process productivity measurement. Such approach is suggested and for other complex technological processes

Determination of mercury traces in products of TiO2_2 manufacturing

A simple method for the determination of mercury traces in co-products and final products of titanium (IV) oxide manufacturing was developed. It was shown that different procedures recommended for the total digestion of such materials (using mixtures of HF, HNO3, HCl and HClO4) could be efficiently replaced by an unique partial digestion method based on mercury leaching from sample by HNO3. Partial digestion method was much quicker and more sensitive than total digestion methods. Mercury was detected with cold vapour atomic fluorescence spectroscopy and a detection limit of 10 pgHg/g was achieved. The method was validated using certified reference materials PACS-1 (NRCC) and maroccan phosphate rock (BCR). Regarding mercury content in analysed samples from the point of view of the ecological risk, only residual material after first digestion of raw material with H2SO4 were found to contain mercury concentrations higher than accepted background value for sediment and soils (0.1 μgHg/g). All other co-products as well as the final product titanium (IV) oxide were almost free of mercury (< 0.01 - 30 ngHg/g)

Microwave-assisted determination of total mercury and methylmercury in sediment and porewater

Existing methods for total mercury and methylmercury determination in sediment and porewaters were improved by applying open microwave heating for extraction of Hg species from the sample and decomposition of MeHg prior to detection as Hg(II) by CV AFS. It was shown that nitric acid can quantitatively leach Hg from sediment, already at a low microwave power (30 W, 5 min). Methylmercury can be quantitatively leached from sediment by dilute sulphuric acid (1 mol/L) at a power of 60 W during 5 minutes, without being decomposed. So obtained extract can be further distilled with a reduced possibility for artefactual MeHg formation, as it contains much lower levels of inorganic Hg, compared to the original sediment. Microwave-assisted BrCl oxidation was shown to be more effective for decomposition of MeHg and stable organomercury complexes in water solutions (sediment distillate and porewater), as compared with BrCl oxidation at room-temperature. Therefore, the application of low-power microwave digestion can significantly improve determination of Hg species in sediment and porewater, both in terms of time and efficiency

Organotin persistence in contaminated marine sediments and porewaters: In situ degradation study using species-specific stable isotopic tracers

International audienceThis paper provides a comprehensive study of the persistence of butyltins and phenyltins in contaminated marine sediments and presents the first data on their degradation potentials in porewaters. The study's aim was to explain the different degradation efficiencies of organotin compounds (OTC) in contaminated sediments. The transformation processes of OTC in sediments and porewaters were investigated in a field experiment using species-specific, isotopically enriched organotin tracers. Sediment characteristics (organic carbon content and grain size) were determined to elucidate their influence on the degradation processes. The results of this study strongly suggest that a limiting step in OTC degradation in marine sediments is their desorption into porewaters because their degradation in porewaters occurs notably fast with half-lives of 9.2 days for tributyltin (TBT) in oxic porewaters and 2.9 ± 0.1 and 9.1 ± 0.9 days for dibutyltin (DBT) in oxic and anoxic porewaters, respectively. By controlling the desorption process, organic matter influences the TBT degradation efficiency and consequently defines its persistence in contaminated sediments, which thus increases in sediments rich in organic matter. © 2015 Elsevier B.V