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  • 1
    Electronic Resource
    Electronic Resource
    H2S adsorption on chromium, chromia, and gold/chromia surfaces: Photoemission studies (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9146-9156 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of H2S with chromium, chromia, and Au/chromia films grown on a Pt(111) crystal has been investigated using synchrotron-based high-resolution photoemission spectroscopy. At 300 K, H2S completely decomposes on polycrystalline chromium producing a chemisorbed layer of S that attenuates the Cr 3d valence features. No evidence was found for the formation of CrSx species. The dissociation of H2S on Cr3O4 and Cr2O3 films at room temperature produces a decrease of 0.3–0.8 eV in the work function of the surface and significant binding-energy shifts (0.2–0.6 eV) in the Cr 3p core levels and Cr 3d features in the valence region. The rate of dissociation of H2S increases following the sequence: Cr2O3〈Cr3O4〈Cr. For chromium, the density of states near the Fermi level is large, and these states offer a better match in energy for electron acceptor or donor interactions with the frontier orbitals of H2S than the valence and conduction bands of the chromium oxides. This leads to a large dissociation probability for H2S on the metal, and a low dissociation probability for the molecule on the oxides. In the case of Cr3O4 and Cr2O3, there is a correlation between the size of the band gap in the oxide and its reactivity toward H2S. The uptake of sulfur by the oxides significantly increases when they are "promoted" with gold. The Au/Cr2O3 surfaces exhibit a unique electronic structure in the valence region and a larger ability to dissociate H2S than polycrystalline Au or pure Cr2O3. The results of ab initio SCF calculations for the adsorption of H2S on AuCr4O6 and AuCr10O15 clusters show a shift of electrons from the gold toward the oxide unit that enhances the strength of the Au(6s)↔H2S(5a1,2b1) bonding interactions and facilitates the decomposition of the molecule. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475319
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  • 2
    Electronic Resource
    Electronic Resource
    MASTER EQUATIONS, STOCHASTIC DIFFERENTIAL EQUATIONS, AND BIFURCATIONS (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 316 (1979), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1979.tb29488.x
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  • 3
    Electronic Resource
    Electronic Resource
    Time-convolutionless projection operator formalism for elimination of fast variables. Applications to Brownian motion (1979)
    Springer
    The European physical journal 35 (1979), S. 297-308 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The relation between the time-convolutionless projection operator formalism and the methods developed by Kubo and van Kampen in the context of linear stochastic differential equations is discussed in detail. It is shown how this formalism may be used to develop a systematic procedure for the elimination of “fast variables”. This procedure is applied to the case of a free Brownian particle and to that of a heavily damped Brownian particle in the presence of an external force to obtain a reduced description in terms of the position variable: the results are found to be in complete agreement with the previous works on this problem. The rotational Brownian motion of an asymmetrical top in the presence of an external torque is also considered and an equation for the reduced probability distribution is derived which contains all the previous works on this problem as special cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01319852
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  • 4
    Electronic Resource
    Electronic Resource
    A trend in the C-O bond strength ofCH3O(ad) on NiAl(100), FeAl(100) andTiAl(010). Effect of the alloy Fermi level (1997)
    Springer
    Catalysis letters 47 (1997), S. 105-109 
    Details
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Research is presented that investigates the C-O bond stability of surface methoxy bound on Al-terminated NiAl(100), FeAl(100), and TiAl(010).Temperature-programmed desorption suggests that a fraction of methoxy individually bound on the Al component of all three surfaces undergoes C-O bond cleavage to evolve gaseous methyl radicals. The trend in the temperature of maximum methyl ejection rate, Tm, is as follows :Tm(NiAl)〉Tm(FeAl)〉Tm(TiAl), suggesting that the nature of the transition metal in the underlying layer affects of the C-O bond energy. Results are shown that suggest that the position of the Fermilevel in these materials plays a role in determining the C-O bond strength, consistent with the prediction of recent theory by Shiller and Anderson.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019040618087
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  • 5
    Electronic Resource
    Electronic Resource
    Oscillations and fluctuations in a dissipative spin system (1979)
    Springer
    The European physical journal 36 (1979), S. 195-204 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A dissipative spin system, which is also considered to be a model for optical fluorescence, is investigated from the viewpoint of Brownian motion of spins. The most probable path and the fluctuations are determined by the quantum mechanical version of the system size expansion method. For the most probable path, the flow lines as well as the time evolutions are obtained exactly. This system exhibits a sort of nonequilibrium phase transition as the strength of an external field exceeds the dissipation. The fluctuations show unusual behaviour associated with the Volterra-like oscillations above threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320220
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  • 6
    Electronic Resource
    Electronic Resource
    The poisson representation. I. A new technique for chemical master equations (1977)
    Springer
    Journal of statistical physics 17 (1977), S. 429-468 
    Details
    ISSN: 1572-9613
    Keywords: Chemical reactions ; correlations ; fluctuations ; instabilities ; stochastic differential equations ; master equations ; reaction diffusion systems ; statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We introduce a new technique for handling chemical master equations, based on an expansion of the probability distribution in Poisson distributions. This enables chemical master equations to be transformed into Fokker-Planck and stochastic differential equations and yields very simple descriptions of chemical equilibrium states. Certain nonequilibrium systems are investigated and the results are compared with those obtained previously. The Gaussian approximation is investigated and is found to be valid almost always, except near critical points. The stochastic differential equations derived have a few novel features, such as the possibility of pure imaginary noise terms and the possibility of higher order noise, which do not seem to have been previously studied by physicists. These features are allowable because the transform of the probability distribution is a quasiprobability, which may be negative or even complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01014349
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  • 7
    Electronic Resource
    Electronic Resource
    The poisson representation. II Two-time correlation functions (1978)
    Springer
    Journal of statistical physics 18 (1978), S. 501-522 
    Details
    ISSN: 1572-9613
    Keywords: Master equations ; chemical reactions ; reaction-diffusion systems ; Poisson representation ; two-time correlation functions ; fluctuation-dissipation theorems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Basic formulas for the two-time correlation functions are derived using the Poisson representation method. The formulas for the chemical system in thermodynamic equilibrium are shown to relate directly to the fluctuationdissipation theorems, which may be derived from equilibrium statistical mechanical considerations. For nonequilibrium systems, the formulas are shown to be generalizations of these fluctuation-dissipation theorems, but containing an extra term which arises entirely from the nonequilibrium nature of the system. These formulas are applied to two representative examples of equilibrium reactions (without spatial diffusion) and to a nonequilibrium chemical reaction model (including the process of spatial diffusion) for which the first two terms in a systematic expansion for the two-time correlation functions are calculated. The relation between the Poisson representation method and Glauber-SudarshanP-representation used in quantum optics is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01014520
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  • 8
    Electronic Resource
    Electronic Resource
    Stochastic analysis of a chemical reaction with spatial and temporal structures (1977)
    Springer
    Journal of statistical physics 17 (1977), S. 469-489 
    Details
    ISSN: 1572-9613
    Keywords: Brusselator ; chemical reactions ; chemical oscillations ; correlations ; fluctuations ; instabilities ; Langevin equations ; master equations ; Poisson representation ; reaction-diffusion systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A stochastic analysis of the spatial and temporal structures in the Prigogine-Lefever-Nicolis model (the Brusselator) is presented. The analysis is carried out through a Langevin equation derived from a multivariate master equation using the Poisson representation method, which is used to calculate the spatial correlation functions and the fluctuation spectra in the Gaussian approximation. The case of an infinite three-dimensional system is considered in detail. The calculations for the spatial correlation functions and the fluctuation spectra for a finite system subject to different kinds of boundary conditions are also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01014350
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  • 9
    Electronic Resource
    Electronic Resource
    Service of high-alumina refractories in ARC furnaces (1995)
    Springer
    Refractories and industrial ceramics 36 (1995), S. 262-264 
    Details
    ISSN: 1573-9139
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Specimens taken from the inlets of the electrodes of an arc furnace and the near zone after service are investigated. It is established that the porous structure of the specimens caused by mullitization at high temperatures intensifies the effect of slag on the refractory material. The process leads to the formation of hercynite, ringwoodite, and spinel. The formation of hercynite reduces the service life of linings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02227399
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  • 10
    Electronic Resource
    Electronic Resource
    Integrated Manufacturing System for Precision Press Tooling (1999)
    Springer
    The international journal of advanced manufacturing technology 15 (1999), S. 356-365 
    Details
    ISSN: 1433-3015
    Keywords: Key words.Integrated manufacturing; NC programs; Press tools; Process planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The press tooling industry, characterised by many small-scale job-shops, is facing an increasingly competitive global market. This comes at a time when there is a shortage of experienced process planners and unavailability of affordable CAD/CAM systems that could provide an integrated solution for manufacturing sheet metal tooling. Many commercially available CAD/CAM systems are either too expensive or too narrow in scope, in the sense that they provide only point solutions. The design of press tools and its manufacturing functions are highly specialised and knowledge-intensive in nature. This paper presents a framework and the implementation details of an integrated system that has been developed for a local sheet metal tooling company specialising in precision punches and dies. A PC-based system has been implemented on an AutoCAD platform using the Autolisp programming language.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001700050078
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