Sökning: "periodic surfaces"

Visar resultat 21 - 25 av 54 avhandlingar innehållade orden periodic surfaces.

  1. 21. Catalytic Water Production from First-Principles Calculations

    Författare :Gustav Karlberg; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; platinum; Monte Carlo; first-principles; hydroxyl; transition metals; density functional theory DFT ; Metropolis; oxygen; water; water production reaction; hydrogen;

    Sammanfattning : The main subject of this thesis is the catalytic water production reaction on metal surfaces. This reaction is of great current interest due to its importance in fuel cells, a clean and efficient way to convert chemical energy into electrical. LÄS MER

  3. 22. Polar molecules in crystalline and surface environments : From first principles

    Författare :Maria Alfredsson; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Chemistry; Kemi; Chemistry; Kemi; Inorganic Chemistry; oorganisk kemi;

    Sammanfattning : With the knowledge of the composition and structure of a chemical system, be it a molecule, a two-dimensional surface or a three-dimensional crystal, it is now possible to predict the specific properties of the compound under consideration via computational studies. Molecular and periodic Hartree-Fock and DFT calculations have been used as a tool to study polar molecules and how their properties respond to the molecular environment in a crystal or on an ionic surface. LÄS MER

  4. 23. Influence of Material Variations on Machinability - Machining Difficult-to-Machine Alloys

    Författare :Stefan Cedergren; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Alloy 718; Superalloys; Ti-6Al-4V; segmented chip; 316L;

    Sammanfattning : The aim of this study is to investigate the effect of work material variations on machinability. Improved knowledge in this respect supports the development of sustainable production both from resource and economical points of view.The properties of work materials vary greatly depending on how they were manufactured. LÄS MER

  5. 24. Towards a Chemisorption Model for Transition-Metal Nitrides and Carbides from Density-Functional Theory: A TiN and TiC Case Study

    Författare :Aleksandra Vojvodic; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Titanium; Titanium nitride; Transition-metal nitrides and carbides;

    Sammanfattning : Since the 1960's, a number of models for chemisorption on metals has beenpresented, most notably the Anderson-Grimley-Newns model for metals and thed-band model of Hammer and Nørskov for transition metals. The intention of this thesis is to explore the adsorption on transition-metal nitrides andcarbides, technologically interesting materials (in, e. LÄS MER

  7. 25. Absorption Characteristics of Periodically Perforated Suspended Ceilings

    Författare :Dag Holmberg; Teknisk akustik; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Building construction; Byggnadsteknik; measurement device.; flow resistance; suspended ceilings; periodically perforated facing; resonant absorbers; Room acoustics; building acoustics;

    Sammanfattning : The sound absorption characteristics of resonant absorbers, implemented as perforated suspended inner ceilings attached with thin porous layers, are investigated. Several existing theories model the principal absorption mechanisms, but the interaction with the outer sound field influences the absorption in ways that can be modelled with new approaches. LÄS MER