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31.
Atmospheric chemistry and physics in the atmosphere of a developed megacity (London): An overview of the REPARTEE experiment and its conclusions
Roy M Harrison, Manuel DallOsto, David C S Beddows, Alistair J Thorpe, William J Bloss, James D Allan, Hugh Coe, James R Dorsey, Martin W Gallagher, Claire Martin, John Whitehead, Paul I Williams, Roderick L Jones, Justin M Langridge, A K Benton, Stephen M Ball, Ben Langford, C Nicholas Hewitt, Brian Davison, Damien Martin, K Fredrik Peterson, Stephen J Henshaw, Iain R. White, Dudley E Shallcross, Janet F Barlow, Tyrone Dunbar, Fay Davies, Eiko Nemitz, Gavin J Phillips, Carole Helfter, Chiara F Di Marco, Steven Smith, 2012, pregledni znanstveni članek

Opis: The Regents Park and Tower Environmental Experiment (REPARTEE) comprised two campaigns in London in October 2006 and October/November 2007. The experiment design involved measurements at a heavily trafficked roadside site, two urban background sites and an elevated site at 160-190 m above ground on the BT Tower, supplemented in the second campaign by Doppler lidar measurements of atmospheric vertical structure. A wide range of measurements of airborne particle physical metrics and chemical composition were made as well as measurements of a considerable range of gas phase species and the fluxes of both particulate and gas phase substances. Significant findings include (a) demonstration of the evaporation of traffic-generated nanoparticles during both horizontal and vertical atmospheric transport; (b) generation of a large base of information on the fluxes of nanoparticles, accumulation mode particles and specific chemical components of the aerosol and a range of gas phase species, as well as the elucidation of key processes and comparison with emissions inventories; (c) quantification of vertical gradients in selected aerosol and trace gas species which has demonstrated the important role of regional transport in influencing concentrations of sulphate, nitrate and secondary organic compounds within the atmosphere of London; (d) generation of new data on the atmospheric structure and turbulence above London, including the estimation of mixed layer depths; (e) provision of new data on trace gas dispersion in the urban atmosphere through the release of purposeful tracers; (f) the determination of spatial differences in aerosol particle size distributions and their interpretation in terms of sources and physico-chemical transformations; (g) studies of the nocturnal oxidation of nitrogen oxides and of the diurnal behaviour of nitrate aerosol in the urban atmosphere, and (h) new information on the chemical composition and source apportionment of particulate matter size fractions in the atmosphere of London derived both from bulk chemical analysis and aerosol mass spectrometry with two instrument types.
Ključne besede: megacity, trace gas, urban atmosphere, atmospheric transport, chemical composition, aerosol
Objavljeno v RUNG: 18.07.2019; Ogledov: 3189; Prenosov: 0
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32.
Regional biodiversity and seasonal dynamics of the bacterial communities in karstic springs of Slovenia
Maja Opalički Slabe, 2019, doktorska disertacija

Opis: Information on groundwater’s natural bacterial communities is important for evaluating pristine groundwater’s quality, as environmental changes potentially lead to alterations in bacterial community structures. In four seasons, 15 hypothetically pristine springs across five karst eco-regions in Slovenia (Central Europe) were analysed during their low discharge, and their basic physical and chemical parameters were recorded. The diversity of bacterial community structures was assessed with a terminal restriction fragment length polymorphism fingerprinting method. Total cell counts as bacterial abundance and electron transport system activity as bacterial respiratory activity were used for quantitative evaluation of bacterial communities. To detect anthropogenic pollution, spring water was tested by the cultivation of coliform bacteria and Escherichia coli (E. coli). Results indicate distinct regional differences in environmental parameters, bacterial respiratory activity, presence of coliforms and E. coli, bacterial abundances, and qualitative bacterial community structures, but there were no regional differences in the numbers of operational taxonomic units and biodiversity indices (Shannon-Wiener’s and Simpson’s diversity index, Buzas and Gibson’s evenness). The analysis of seasonal environmental parameters showed significant differences in dissolved organic carbon and pH, and also significant changes in bacterial respiratory activity and abundances, as well as differences in bacterial community structures, the numbers of operational taxonomic units, and biodiversity indices. No seasonal variations were shown for coliforms and E. coli. Despite seasonal oscillations, regional differences prevailed among five karst eco-regions and indicate a significant influence on the qualitative and quantitative aspects of groundwater bacterial community structures. The study confirmed both regional and seasonal differences in groundwater bacterial community structures, which should be included in further sustainable management plans of the aquifers.
Ključne besede: karst springs, bacterial community structure (BCS), terminal restriction fragment length polymorphism (T-RFLP), total cell counts (TCC), electron transport system activity (ETSA)
Objavljeno v RUNG: 26.06.2019; Ogledov: 3720; Prenosov: 184
.pdf Celotno besedilo (3,76 MB)

33.
Role of transport band edge variation on delocalized charge transport in high-mobility crystalline organic semiconductors
Gvido Bratina, Andrey Kadashchuk, Egon Pavlica, Fei Tong, 2017, izvirni znanstveni članek

Opis: We demonstrate that the degree of charge delocalization has a strong impact on polarization energy and thereby on the position of the transport band edge in organic semiconductors. This gives rise to long-range potential fluctuations, which govern the electronic transport through delocalized states in organic crystalline layers. This concept is employed to formulate an analytic model that explains a negative field dependence coupled with a positive temperature dependence of the charge mobility observed by a lateral time-of-flight technique in a high-mobility crystalline organic layer. This has important implications for the further understanding of the charge transport via delocalized states in organic semiconductors.
Ključne besede: organic semiconducotrs, time of flight, transport
Objavljeno v RUNG: 13.09.2017; Ogledov: 4213; Prenosov: 0
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34.
The role of local potential minima on charge transport in thin organic semiconductor layers
Egon Pavlica, Raveendra Babu Penumala, Gvido Bratina, 2016, izvirni znanstveni članek

Opis: We have performed a systematic study of dependence of time-resolved photocurrent on the point of charge excitation within the organic semiconductor channel formed by two coplanar metal electrodes. The results confirm that spatial variation of electric field between the electrodes crucially determines transport of photogenerated charge carriers through the organic layer. Time-of-flight measurements of photocurrent demonstrate that the transit time of photogenerated charge carrier packets drifting between the two electrodes decreases with increasing travelling distance. Such counterintuitive result cannot be reconciled with the spatial distribution of electric field between coplanar electrodes, alone. It is also in contrast to expected role of space-charge screening of external electric field. Supported by Monte Carlo simulations of hopping transport in disordered organic semiconductor layer, we submit that the space-charge screens the external electric field and captures slower charge carriers from the photogenerated charge carrier packet. The remaining faster carriers, exhibit velocity distribution with significantly higher mean value and shorter transit time.
Ključne besede: Charge transport, Organic semiconductors, Time of flight, Mobility, Traps
Objavljeno v RUNG: 23.12.2016; Ogledov: 5287; Prenosov: 0
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35.
Transport električnega naboja v organskih polprevodnikih, simulacija po metodi Monte Carlo
Robert Hudej, Gvido Bratina, Egon Pavlica, 2003, izvirni znanstveni članek

Opis: The electric-charge transport in organic semiconductors is essentially different to the transport in ordered inorganic crystals. The reason is in thelocalization of the energy states, which act as charge-carrier transport channels between molecules. Consequently, the determination of the basic transport parameters in organic materials is inherently more involved than in their inorganic counterparts. The analytical methods that are used to describe charge transport in inorganic materials are unsuitable, since they are based on the extended electronic energy structure. We report here on the simulation of charge transport in organic semiconductor thin films. The simulation is based on the Monte Carlo method and describes the charge-carrier transport within the framework of carrier hopping between the sites. We employed a Gaussian energy distribution of the hopping sites with disorder elements. The degree of disorder is characterized by the width of the Gaussian distribution and is measured in eV units. The results of the transport simulation in 3,4,9,10-perylenedianhydride tetracarboxylic acid (PTCDA) show that the photogenerated charge-carrier current depends on the film thickness, temperature and disorder degree. The simulated photocurrents have the same amplitude in thick films as in the thin films, but the overall shape of the I(t) curve is more dispersive in thin films. The charge-carrier mobility decreases with the increasing degree of disorder at a given temperature. The simulation of the photogenerated positive charge carriers current matches with the time-of-flight experiment in a glass/ITO/PTCDA(600 nm)/In heterostructure at room temperature and an applied bias voltage of 8 V.
Ključne besede: neurejeni kristali, metoda Monte Carlo, organski polprevodniki, transport naboja, PTCDA, tranzientne meritve
Objavljeno v RUNG: 10.07.2015; Ogledov: 5820; Prenosov: 23
URL Povezava na celotno besedilo

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Gospodarjenje z opažnim materialom v gradbenem podjetju
Igor Medvešček, 2005, diplomsko delo

Opis: Diplomska naloga se začenja z opredelitvijo logistike in njenega pomena v podjetju. Tu so predstavljene ključne točke, s katerimi skuša logistika čim racionalnejše reševati probleme v premagovanju prostora in časa. Nadaljuje se s predstavitvijo gradbenega podjetja, njegovega informacijskega sistema in opažnega materiala, ki ga podjetje uporablja pri gradnji. Sledi analiza logističnega poslovanja z opažnim materialom od njegovega naročila, prejema, skladiščenja, izdajanja, transporta in ponovno vračanja nazaj v skladišče. V zadnjem delu so predstavljene ugotovitve in predlagane rešitve nastalih problemov.
Ključne besede: diplomske naloge, logistika, gradbeno podjetje, informacijski sistem, opažni material, skladišče, nabava, transport
Objavljeno v RUNG: 15.10.2013; Ogledov: 6259; Prenosov: 836
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39.
Zunanja oskrba notranjega transporta Iskra Avtoelektrika
Matej Frančeškin, 2011, diplomsko delo

Ključne besede: diplomske naloge, podjetja, zunanja oskrba, operativni lizing, transport, ekonomska ocena
Objavljeno v RUNG: 15.10.2013; Ogledov: 4666; Prenosov: 413
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40.
Borze prevozov in tovorov na internetu
Damjana Dolanc, 2011, diplomsko delo

Ključne besede: diplomske naloge, logistika, transport, borze prevozov, borze tovorov, spletne aplikacije
Objavljeno v RUNG: 15.10.2013; Ogledov: 5742; Prenosov: 413
URL Povezava na celotno besedilo
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