Racionalizacija procesa nabave storitev v gradbenem podjetjuBoštjan Kovač
, 2005, undergraduate thesis
Abstract: Nabavna funkcija je ena izmed osnovnih poslovnih funkcij vsakega podjetja. Nabava storitev je tista poslovna funkcija, ki pravočasno, po primerni ceni, s potrebno količino in ustrezno kakovostjo, oskrbuje inženirska podjetja s storitvami. Zagotoviti mora tudi potrebne informacije ostalim poslovnim funkcijam podjetja ter vzpostavljati in vzdrževati dobre stike z dobavitelji. V okviru diplomske naloge je moj namen prikazati pomen managementa nabave za sodobno poslovanje podjetja. V prvem delu naloge sem teoretično obdelal značilnosti sodobnega poslovanja in ugotovil, da ima nabavna funkcija vedno večji pomen. Prav tako v prvem delu naloge navajam cilje in naloge nabave ter poudarek na sodelovanju nabave z drugimi funkcijami v podjetju, ki je ključnega pomena za uspeh podjetja. V drugem delu diplomske naloge sem naredil analizo nabavne funkcije v konkretnem podjetju ter navedel predloge za racionalizacijo nabavnega procesa, ki bi prispevala k uspešnejšemu poslovanju celotnega podjetja.
Found in: osebi
Keywords: diplomske naloge, nabavni poces, kooperant, kooperacija, nabava storitev, partner, pogodba
Published: 15.10.2013; Views: 5394; Downloads: 537
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Removal of manganese in batch and fluidized bed systems using beads of zeolite a as adsorbentBojana Obradovic
, Nataša Novak Tušar
, Iztok Arčon
, Janez Kovač
, Mina Jovanovic
, Nevenka Rajić
, 2016, original scientific article
Abstract: In this study the uptake capacity of Mn(II) ions by zeolite A beads was investigated for different initial Mn concentration (100e400 mg Mn dm^-3) in batch mode at 25e55 C. The obtained adsorption capacity varying from 30 to 50 mg Mn g^-1 demonstrated a high affinity of zeolite A towards Mn(II) present in solutions. Kinetic studies indicated the intra-particle diffusion as the rate limiting step up to 45 C with apparent diffusivities in the range (1.2e2.0) x 10^-13 m2 s^-1 and the activation energy of 21.9 kJ mol^-1, which implies strong interactions between the zeolite A and Mn ions. At 55 C ion-exchange became the rate limiting step. The adsorption isotherms were studied at 25 C showing that the Mn adsorption is the best described by the Langmuir model suggesting a homogenous zeolite surface. XPS analysis of the Mnloaded beads showed that there is no surface accumulation of Mn but an almost uniform Mn distribution inside zeolite A, whereas XANES and EXAFS suggested that the adsorption of Mn(II) was followed by the Mn(II) oxidation and oxide formation. Regeneration of the spent zeolite was examined in 8 adsorption/desorption cycles by a chelating Na2EDTA in a fluidized column. It has been found that zeolite A beads could be reused for at least 4 cycles with satisfactory Mn(II) adsorption efficiencies of about 70%.
Found in: osebi
Keywords: Zeolite A
Published: 01.04.2016; Views: 3889; Downloads: 0
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Effect of the Morphology of the High-Surface-Area Support on the Performance of the Oxygen-Evolution Reaction for Iridium NanoparticlesLeonard Moriau
, Marjan Bele
, Živa Marinko
, Francisco Ruiz-Zepeda
, Gorazd Koderman
, Martin Šala
, Angelija Kjara Šurca
, Janez Kovač
, Iztok Arčon
, Primož Jovanovič
, Nejc Hodnik
, Luka Suhadolnik
, 2021, original scientific article
Abstract: The development of affordable, low-iridium-loading,
scalable, active, and stable catalysts for the oxygen-evolution
reaction (OER) is a requirement for the commercialization of
proton-exchange membrane water electrolyzers (PEMWEs).
However, the synthesis of high-performance OER catalysts with
minimal use of the rare and expensive element Ir is very challenging
and requires the identification of electrically conductive and stable
high-surface-area support materials. We developed a synthesis
procedure for the production of large quantities of a nanocomposite
powder containing titanium oxynitride (TiONx) and Ir.
The catalysts were synthesized with an anodic oxidation process
followed by detachment, milling, thermal treatment, and the
deposition of Ir nanoparticles. The anodization time was varied to grow three different types of nanotubular structures exhibiting different lengths and wall thicknesses and thus a variety of properties. A comparison of milled samples with different degrees of nanotubular clustering and morphology retention, but with identical
chemical compositions and Ir nanoparticle size distributions and dispersions, revealed that the nanotubular support morphology is
the determining factor governing the catalyst’s OER activity and stability. Our study is supported by various state-of-the-art
materials’ characterization techniques, like X-ray photoelectron spectroscopy, scanning and transmission electron microscopies, Xray powder diffraction and absorption spectroscopy, and electrochemical cyclic voltammetry. Anodic oxidation proved to be a very suitable way to produce high-surface-area powder-type catalysts as the produced material greatly outperformed the IrO2 benchmarks
as well as the Ir-supported samples on morphologically different TiONx from previous studies. The highest activity was achieved for the sample prepared with 3 h of anodization, which had the most appropriate morphology for the effective removal of oxygen
Found in: osebi
Keywords: electrocatalysis, oxygen-evolution reaction, TiONx-Ir powder catalyst, iridium nanoparticles, anodic oxidation, morphology−activity correlation
Published: 04.01.2021; Views: 1272; Downloads: 0
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Extraction of Organochlorine Pesticides from Plastic Pellets and Plastic Type AnalysisŠpela Koren
, Manca Kovač Viršek
, Petra Makorič
, Maryline Pflieger
, 2017, review article
Abstract: Plastic resin pellets, categorized as microplastics (≤5 mm in diameter), are small granules that can be unintentionally released to the
environment during manufacturing and transport. Because of their environmental persistence, they are widely distributed in the oceans and
on beaches all over the world. They can act as a vector of potentially toxic organic compounds (e.g., polychlorinated biphenyls) and might
consequently negatively affect marine organisms. Their possible impacts along the food chain are not yet well understood. In order to assess the
hazards associated with the occurrence of plastic pellets in the marine environment, it is necessary to develop methodologies that allow for rapid
determination of associated organic contaminant levels. The present protocol describes the different steps required for sampling resin pellets,
analyzing adsorbed organochlorine pesticides (OCPs) and identifying the plastic type. The focus is on the extraction of OCPs from plastic pellets
by means of a pressurized fluid extractor (PFE) and on the polymer chemical analysis applying Fourier Transform-InfraRed (FT-IR) spectroscopy.
The developed methodology focuses on 11 OCPs and related compounds, including dichlorodiphenyltrichloroethane (DDT) and its two main
metabolites, lindane and two production isomers, as well as the two biologically active isomers of technical endosulfan. This protocol constitutes
a simple and rapid alternative to existing methodology for evaluating the concentration of organic contaminants adsorbed on plastic pieces.
Found in: osebi
Keywords: Environmental Sciences, Issue 125, Microplastics, resin pellets, pesticides, persistent organic pollutants, organochlorine pesticides, dichlorodiphenyltrichloroethane, endosulfan, hexachlorocyclohexane, lindane, Fourier transform infrared spectroscopy, pressurized fluid extractor
Published: 10.07.2017; Views: 3068; Downloads: 0
Speleogenetic factors and processes in the karst conduits of Zagorska Mrežnica Spring Cave (Croatia)Petra Kovač Konrad
, 2018, doctoral dissertation
Abstract: Zagorska Mrežnica spring cave is in the Desmerice village, 7.59 km SW from the town of Ogulin. The coordinates of the entrance are X: 399563 m, Y: 5006974 m, and Z: 314 m (HTRS96). The cave system is positioned in the contact zone of Jurassic limestone and the thrust front composed of Triassic Dolomite. The karst drainage system has elements of point recharge through a set of ponors in the hinterland karst poljes and diffuse infiltration through numerous dolines on Velika Kapela Mountain. The karst of Ogulinsko Zagorje area and its epiphreatic and phreatic cave systems have been intensively explored for the last eight years, resulting in the mapping of 1134 m of submerged passages of the Zagorska Mrežnica spring cave. Until 2014 it was the longest mapped submerged system in Croatia explored by cave diving techniques only. Altogether, over 3.5 km of submerged passages in seven caves of Ogulinsko Zagorje (Zagorska Mrežnica spring cave, Spring of Rupečica, Ponor of Rupečica, Cave system Pećine-Veliko vrelo, Spring of Bistrac, Cave Zagorska Peć and Pit Klisura) were explored during 500 hours of diving over a ten-year period. The goal of the research was to determine speleogenetic factors and processes in phreatic conditions. A new methodology for mapping of cave cross-sections, microrelief forms, and structural elements was developed, sediment and petrographic analysis were done, hydrological analysis before and after the building of the accumulation lake Sabljaci, 48 cross-sections of the cave passaged and a 3D model of the cave system was created, water chemistry as well as geomorphological analysis was carried out. In the end, a simplified (modified) vulnerability assessment was also done.
The results of my research showed that the distribution of the cave passages is a result of complex tectonic activities that are reflected in the orientation of cave passages. The general orientation of the measured fissures, measured during cave diving, show a dominance of a NWW-SEE direction but also the pattern of cave passages shows a significant dominance of the NE-SW orientation indicating the existence of multiple secondary traverse faults originating from main NW-SE faults. The morphology of the cave passages shows a transition between epiphreatic (possibly vadose) and phreatic phases as well as the presence of paragenetic developments in the ceiling. This indicates the existence of several epiphreatic (possibly vadose) and phreatic speleogenetic phases. The initial shape of the cross-sections was identified by sub-horizontal beds and bedding planes. The mapping of microrelief forms showed that the mechanical erosion was a very intensive process shaping the morphology of the cave passages.
The sediment mineralogy coincides with the lithology of the catchment area, and the sub- angular grains reveal relatively short transport distances. Further analysis of the catchment area’s geomorphology and its relevance for the speleogenesis of Zagorska Mrežnica cave show influence of relief structures that have a Dinaric orientation (NW-SE) with cave structures and passage orientations, great relative relief, steep slopes on Velika Kapela, and flat areas of karst poljes dictate the allogenic and autogenic hydrological regime of the cave. A 3D model of the cave system reveals a relationship between the cave system and the landscape, as well as a possible connection with the nearby Zagorska Peć cave. The modified karst vulnerability assessment shows that the catchment area of Zagorska Mrežnica spring cave has a high vulnerability ranking, mainly due to high doline density and the potential large diffuse capacity of infiltration of pollutants.
Found in: osebi
Keywords: Ogulin Zagorje, karst, spring, speleogenesis, Zagorska Mrežnica spring cave
Published: 02.03.2018; Views: 3497; Downloads: 138
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Prevzeto izrazje s področja popularnih glasbenih zvrsti in njegova slovarska obravnavaPetra Kovač
, 2019, undergraduate thesis
Abstract: Diplomska naloga obravnava problematiko pisanja prevzetega besedja v slovenskem jeziku. V uvodnem delu se bom najprej posvetila obravnavi problematike prevzemanja besed, načinu prevzemanja v slovenski jezikovni sistem in predstavila tudi historični vidik prevzemanja slovenskih prevzetih besed in besednih zvez. Osrednji del diplomskega dela bo osredotočen na besedje s področja glasbe, zlasti prevzemanje izrazov, povezanih s popularno glasbo. V svojem delu želim ugotoviti, v kateri obliki se posamezni izrazi dejansko uporabljajo, v nepodomačeni ali podomačeni, pri čemer lahko soobstaja več podomačenih različic. S pomočjo korpusa Gigafida bom naredila analizo, s katero bo ugotovljeno, v kolikšni meri jezikovni uporabniki upoštevajo določila normativnih priročnikov glede pisanja prevzetih besed oziroma nasprotno, ali ta pravopisna določila sledijo rabi, ki jo uveljavljajo jezikovni uporabniki. Cilj diplomskega dela je prikazati glavne jezikovne zadrege uporabnikov slovenskega jezika pri zapisovanju besed s področja glasbe, ki smo jih v slovenski jezik prevzeli iz drugih jezikov, in ta opažanja tudi pojasniti.
Found in: osebi
Keywords: Podomačevanje, prevzete besede, glasbene zvrsti
Published: 26.09.2019; Views: 2171; Downloads: 94
Fulltext (1,61 MB)