Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme

Options:
  Reset


11 - 20 / 31
First pagePrevious page1234Next pageLast page
11.
Atomically resolved dealloying of structurally ordered Pt nanoalloy as an oxygen reduction reaction electrocatalyst
Andraž Pavlišič, Primož Jovanovič, Vid Simon Šelih, Martin Šala, Marjan Bele, Goran Dražić, Iztok Arčon, Samo B. Hočevar, Anton Kokalj, Nejc Hodnik, Miran Gaberšček, original scientific article

Abstract: The positive effect of intermetallic ordering of platinum alloy nanoparticles on oxygen reduction reaction (ORR) activity has been well established. What is still missing is an understanding of selective leaching of the less noble metal from the ordered structure and its correlation to longterm ORR performance. Using a combination of kinetic Monte Carlo simulations and advanced characterization techniques, we provide unprecedented insight into dealloying of intermetallic PtCu3 nanoparticles a well-known binary alloy. Comparison of ordered and disordered samples with identical initial compositions and particle size distributions reveals an unexpected correlation: whereas the copper dealloying rates in the ordered and disordered counterparts are almost the same, in the ordered structure Pt atoms are surrounded by 15−30% more Cu atoms throughout all the stages of acid leaching. This more convenient Pt−Cu coordination explains the statistically significant increase of 23−37% in ORR activity of the ordered structure at all stages of alloy degradation.
Found in: ključnih besedah
Summary of found: ...ORR performance. Using a combination of kinetic Monte Carlo simulations and advanced characterization techniques, we...
Keywords: ORR activity, fuel cells, platinum alloy, nanoparticle stability, intermetallic ordering, kinetic Monte Carlo, dealloying, in situ ICP-MS
Published: 27.09.2016; Views: 4129; Downloads: 0
.pdf Fulltext (3,27 MB)

12.
Packing patterns of silica nanoparticles on surfaces of armored polystyrene latex particles
Sara Fortuna, Catheline A. L. Colard, Stefan A. F. Bon, Alessandro Troisi, 2009, original scientific article

Abstract: Fascinating packing patterns of identical spherical and discotic objects on curved surfaces occur readily in nature and science. Examples include C60 fullerenes,(1, 2)13-atom cuboctahedral metal clusters,(3) and S-layer proteins on outer cell membranes.(4) Numerous situations with surface-arranged objects of variable size also exist, such as the lenses on insect eyes, biomineralized shells on coccolithophorids,(5) and solid-stabilized emulsion droplets(6) and bubbles.(7) The influence of size variations on these packing patterns, however, is studied sparsely. Here we investigate the packing of nanosized silica particles on the surface of polystyrene latex particles fabricated by Pickering miniemulsion polymerization of submicrometer-sized armored monomer droplets. We are able to rationalize the experimental morphology and the nearest-neighbor distribution with the help of Monte Carlo simulations. We show that broadening of the nanoparticle size distribution has pronounced effects on the self-assembled equilibrium packing structures, with original 12-point dislocations or grain-boundary scars gradually fading out.
Found in: ključnih besedah
Summary of found: ...the nearest-neighbor distribution with the help of Monte Carlo simulations. We show that broadening of...
Keywords: packing patterns, silica, simulation, Monte Carlo, order, disorder, transition, armored particles, nanoparticles, Pickering emulsion
Published: 10.10.2016; Views: 3390; Downloads: 0
.pdf Fulltext (3,85 MB)

13.
An artificial intelligence approach for modeling molecular self-assembly: Agent Based simulations of rigid molecules
Sara Fortuna, Alessandro Troisi, 2009, original scientific article

Abstract: Agent-based simulations are rule-based models traditionally used for the simulations of complex systems. In this paper, an algorithm based on the concept of agent-based simulations is developed to predict the lowest energy packing of a set of identical rigid molecules. The agents are identified with rigid portions of the system under investigation, and they evolve following a set of rules designed to drive the system toward the lowest energy minimum. The algorithm is compared with a conventional Metropolis Monte Carlo algorithm, and it is applied on a large set of representative models of molecules. For all the systems studied, the agent-based method consistently finds a significantly lower energy minima than the Monte Carlo algorithm because the system evolution includes elements of adaptation (new configurations induce new types of moves) and learning (past successful choices are repeated).
Found in: ključnih besedah
Summary of found: ...algorithm is compared with a conventional Metropolis Monte Carlo algorithm, and it is applied on...
Keywords: Self-assembly, self-organisation, agent based, Monte Carlo, rigid molecules, simulation
Published: 10.10.2016; Views: 3372; Downloads: 0
.pdf Fulltext (2,25 MB)

14.
Hexagonal lattice model of the patterns formed by hydrogen-bonded molecules on the surface
Sara Fortuna, David L. Cheung, Alessandro Troisi, 2010, original scientific article

Abstract: We model the two-dimensional self-assembly of planar molecules capable of complementary interactions (like hydrogen bonding) as a set of hexagonal tiles on a hexagonal lattice. We use Monte Carlo simulations to study the phase diagrams of three model systems. The phases are characterized using a variety of order parameters, and they are studied as a function of the strength of the complementary interaction energy. This simplified model is proven to be capable of reproducing the phases encountered in real systems, unifying within the same framework most of the structures encountered experimentally.
Found in: ključnih besedah
Summary of found: ...tiles on a hexagonal lattice. We use Monte Carlo simulations to study the phase diagrams...
Keywords: self-assembly, self-organisation, Monte Carlo, simulation, lattice model, dicarboxilic acid, hexagonal lattice
Published: 10.10.2016; Views: 3383; Downloads: 0
.pdf Fulltext (3,44 MB)

15.
Agent based modelling for the 2D molecular self-organization of realistic molecules
Sara Fortuna, Alessandro Troisi, 2010, original scientific article

Abstract: We extend our previously developed agent-based (AB) algorithm to the study of the self-assembly of a fully atomistic model of experimental interest. We study the 2D self-assembly of a rigid organic molecule (1,4-benzene-dicarboxylic acid or TPA), comparing the AB results with Monte Carlo (MC) and MC simulated annealing, a technique traditionally used to solve the global minimization problem. The AB algorithm gives a lower energy configuration in the same simulation time than both of the MC simulation techniques. We also show how the AB algorithm can be used as a part of the protocol to calculate the phase diagram with less computational effort than standard techniques.
Found in: ključnih besedah
Summary of found: ...or TPA), comparing the AB results with Monte Carlo (MC) and MC simulated annealing, a...
Keywords: self-assembly, self-organisation, 1, 4-benzene-dicarboxylic acid, TPA, agent based, Monte Carlo, simulation, phase diagram
Published: 11.10.2016; Views: 3497; Downloads: 0
.pdf Fulltext (4,00 MB)

16.
Polymer Vesicles with a Colloidal Armor of Nanoparticles
Rong Chen, Daniel J. G. Pearce, Sara Fortuna, David L. Cheung, Stefan A. F. Bon, 2011, original scientific article

Abstract: The fabrication of polymer vesicles with a colloidal armor made from a variety of nanoparticles is demonstrated. In addition, it is shown that the armored supracolloidal structure can be postmodified through film-formation of soft polymer latex particles on the surface of the polymersome, hereby effectively wrapping the polymersome in a plastic bag, as well as through formation of a hydrogel by disintegrating an assembled polymer latex made from poly(ethyl acrylate-co-methacrylic acid) upon increasing the pH. Furthermore, ordering and packing patterns are briefly addressed with the aid of Monte Carlo simulations, including patterns observed when polymersomes are exposed to a binary mixture of colloids of different size.
Found in: ključnih besedah
Summary of found: ...are briefly addressed with the aid of Monte Carlo simulations, including patterns observed when polymersomes...
Keywords: Pickering emultion, self-assemblt, Monte Carlo, simulation, nanoparticle, packing, pattern garnd canonical, colloids
Published: 11.10.2016; Views: 3273; Downloads: 0
.pdf Fulltext (1,43 MB)

17.
Chelating effect in short polymers for the design of bidentate binders of increased affinity and selectivity
Sara Fortuna, Federico Fogolari, Giacinto Scoles, 2015, original scientific article

Abstract: The design of new strong and selective binders is a key step towards the development of new sensing devices and effective drugs. Both affinity and selectivity can be increased through chelation and here we theoretically explore the possibility of coupling two binders through a flexible linker. We prove the enhanced ability of double binders of keeping their target with a simple model where a polymer composed by hard spheres interacts with a spherical macromolecule, such as a protein, through two sticky spots. By Monte Carlo simulations and thermodynamic integration we show the chelating effect to hold for coupling polymers whose radius of gyration is comparable to size of the chelated particle. We show the binding free energy of flexible double binders to be higher than that of two single binders and to be maximized when the binding sites are at distances comparable to the mean free polymer end-to-end distance. The affinity of two coupled binders is therefore predicted to increase non linearly and in turn, by targeting two non-equivalent binding sites, this will lead to higher selectivity.
Found in: ključnih besedah
Summary of found: ...a protein, through two sticky spots. By Monte Carlo simulations and thermodynamic integration we show...
Keywords: chelation, polymer, multivalency, bidentate, free energy, thermodynamic integration, Monte Carlo
Published: 11.10.2016; Views: 2793; Downloads: 115
.pdf Fulltext (1,68 MB)

18.
Phase behaviour of self-assembled monolayers controlled by tuning physisorbed and chemisorbed states: a lattice-model view
Sara Fortuna, David L. Cheung, Karen Johnston, 2016, original scientific article

Abstract: The self-assembly of molecules on surfaces into 2D structures is important for the bottom-up fabrication of functional nanomaterials, and the self-assembledstructure depends on the interplay between molecule-molecule interactions and molecule-surface interactions. Halogenated benzene derivatives on platinum have been shown to have two distinct adsorption states: a physisorbed state and a chemisorbed state, and the interplay between the two can be expected to have a profound effect on the self-assembly and phase behaviour of these systems. We developed a lattice model that explicitly includes both adsorption states, with representative interactions parameterised using density functional theory calculations. This model was used in Monte Carlo simulations to investigate pattern formation of hexahalogenated benzene molecules on the platinumsurface. Molecules that prefer the physisorbed state were found to self-assemble with ease, depending on the interactions between physisorbed molecules. In contrast, molecules that preferentially chemisorb tend to get arrested in disordered phases. However, changing the interactions between chemisorbed and physisorbed molecules affects the phase behaviour. We propose functionalising molecules in order to tune their adsorption states, as an innovative way to control monolayer structure, leading to a promising avenue for directed assembly of novel 2D structures.
Found in: ključnih besedah
Summary of found: ...theory calculations. This model was used in Monte Carlo simulations to investigate pattern formation of...
Keywords: lattice model, hexagonal lattice, Monte Carlo, DFT, density functional theory, benzene, physisorption, chemisorption, halogenated
Published: 11.10.2016; Views: 3261; Downloads: 0
.pdf Fulltext (5,75 MB)

19.
Zaprtozančno vodenje več-conske peči za kaljenje jeklenic
Matej Gabrijelčič, 2016, master's thesis

Abstract: Več-conske peči za kaljenje jeklenic se v jeklarstvu uporabljajo za izboljševanje mehanskih lastnosti jeklenic. Peč je sestavljena iz več con, v teh spreminjamo temperature z odprtostjo ventilov dovoda energenta za ogrevanje in tako sledimo predpisanim temperaturam iz diagrama procesa kaljenja. Če odprtost ventila za ogrevanje posamezne cone peči vodimo ročno, se lahko zaradi zunanjih motenj pojavi problem pri medsebojnem vplivu sprememb temperatur v conah. To povzroči slabe mehanske lastnosti jeklenic, strošek segrevanja peči se poveča, ob tem pa imamo zagotovljeno tudi slabo varnost ročno vodenega procesa. Opisane slabosti ročno vodenega procesa rešimo z avtomatsko regulacijo. Izbrali in ovrednotili smo metodo vodenja več-conske jeklarske peči za kaljenje jeklenic in pokazali ekonomsko upravičenost avtomatske regulacije. Ugotovili smo, da avtomatsko voden proces sledi zahtevam po ustrezni temperaturi v posamezni coni peči − glede na diagram kaljenja jeklenic −, je varnejši od ročno vodenega, strošek njegove vpeljave pa se povrne v kratkem časovnem obdobju. Zaključimo lahko, da je ustrezno voden proces zanesljiv in velikokrat ponovljiv, predstavlja tisti proces, ki pošilja ustrezne informacije regulatorju procesa preko povratne zanke o tem, kaj se dogaja v posamezni coni peči za kaljenje jeklenic.
Found in: ključnih besedah
Summary of found: ...kaljenje, jeklenica, zaprtozančno vodenje, dinamični sistem, metoda Monte Carlo...
Keywords: več-conska peč, kaljenje, jeklenica, zaprtozančno vodenje, dinamični sistem, metoda Monte Carlo
Published: 06.12.2016; Views: 4753; Downloads: 208
.pdf Fulltext (1,31 MB)

20.
Studies towards an understanding of global array pointing for the Cherenkov Telescope Array
Marko Zavrtanik, Danilo Zavrtanik, Gabrijela Zaharijas, Lili Yang, Serguei Vorobiov, Samo Stanič, Gašper Kukec Mezek, Andrej Filipčič, Stefan Eschbach, 2015, published scientific conference contribution

Found in: ključnih besedah
Summary of found: ...cope Array (CTA), CTA global array pointing, point-source location accuracy, Monte Carlo simulations...
Keywords: Cherenkov Telescope Array (CTA), CTA global array pointing, point-source location accuracy, Monte Carlo simulations
Published: 26.01.2017; Views: 2775; Downloads: 212
.pdf Fulltext (310,22 KB)

Search done in 0 sec.
Back to top