Experiences modelling and using object-oriented telecommunication service frameworks in SDL

This paper describes experiences in using SDL and its associated tools to create telecommunication services by producing and specialising object-oriented frameworks. The chosen approach recognises the need for the rapid creation of validated telecommunication services. It introduces two stages to service creation. Firstly a software expert produces a service framework, and secondly a telecommunications ‘business consultant' specialises the framework by means of graphical tools to rapidly produce services. Here the focus is given to the underlying technology required. In particular, the advantages and disadvantages of SDL and tools for this purpose are highlighted

Oxygen-induced p(2x3) reconstruction on Mo(112) studied by LEED and STM

The open trough-and-row Mo(112) surface serves as substrate for the epitaxial growth of MoO2. In the early stage of oxygen exposure, oxygen chemisorption induces a p(2x3) surface reconstruction of the missing row type on Mo(112). The surface structure of this reconstructed surface has been studied in detail by low-energy electron diffraction and scanning tunneling microscope. The experimental findings can be explained based on the effective medium theory for oxygen adsorption on transition-metal surfaces, providing a structure model for the oxygen-modified Mo(112) surface. The structure model allows the discussion of the oxygen-chemisorbed surface phase as a possible precursor state fo

The comprehensive model system COSMO-ART - Radiative impact of aerosol on the state of the atmosphere on the regional scale

A new fully online coupled model system developed for the evaluation of the interaction of aerosol particles with the atmosphere on the regional scale is described. The model system is based on the operational weather forecast model of the Deutscher Wetterdienst. Physical processes like transport, turbulent diffusion, and dry and wet deposition are treated together with photochemistry and aerosol dynamics using the modal approach. Based on detailed calculations we have developed parameterisations to examine the impact of aerosol particles on photolysis and on radiation. Currently the model allows feedback between natural and anthropogenic aerosol particles and the atmospheric variables that are initialized by the modification of the radiative fluxes. The model system is applied to two summer episodes, each lasting five days, with a model domain covering Western Europe and adjacent regions. The first episode is characterised by almost cloud free conditions and the second one by cloudy conditions. The simulated aerosol concentrations are compared to observations made at 700 stations distributed over Western Europe. <br><br> For each episode two model runs are performed; one where the feedback between the aerosol particles and the atmosphere is taken into account and a second one where the feedback is neglected. Comparing these two sets of model runs, the radiative feedback on temperature and other variables is evaluated. <br><br> In the cloud free case a clear correlation between the aerosol optical depth and changes in global radiation and temperature is found. In the case of cloudy conditions the pure radiative effects are superposed by changes in the liquid water content of the clouds due to changes in the thermodynamics of the atmosphere. In this case the correlation between the aerosol optical depth and its effects on temperature is low. However, on average a decrease in the 2 m temperature is still found. <br><br> For the area of Germany we found on average for both cases a reduction in the global radiation of about 6 W m<sup>2</sup>, a decrease of the 2 m temperature of 0.1 K, and a reduction in the daily temperature range of −0.13 K

Palladium Nanocrystals on Al₂O₃: Structure and Adhesion Energy

We have investigated the structure and morphology of nanosized palladium clusters supported by a thin Al2O3 film on NiAl(110) using scanning tunneling microscopy. Well-ordered clusters with a diameter above ≈40Å were imaged with atomic resolution, allowing a crystallographic identification of the cluster facets. A new method to obtain quantitative information on the work of adhesion (adhesion energy) of metal clusters deposited on oxides is introduced. For Pd on Al2O3 we obtain a value of Wadh=2.8±0.2J/m2. This result is at variance with values recently derived on the basis of ab initio density-functional theory

Transition from a molecular to a metallic adsorbate system: Core-hole creation and decay dynamics for CO coordinated to Pd

Two alternative methods to experimentally monitor the development of a CO-adsorption system that gradually changes from molecular to metallic are presented: firstly by adsorption of CO on Pd islands of increasing size deposited under UHV conditions, and secondly by growth of a Pd carbonyl-like species, formed by Pd deposition in CO atmosphere. The change in screening dynamics as a function of the number of metal atoms was investigated, using x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and core-hole-decay techniques. For CO adsorbed on UHV-deposited islands, the electronic properties of the whole CO-Pd complex is strongly dependent on island size and CO coverage: large amounts of CO result in a reduced screening ability, and small effects characteristic of molecular systems can be detected even for islands containing about 100 Pd atoms. If about half of the CO overlayer is desorbed, the CO-Pd complex exhibits a relaxation upon core ionization that is nearly as efficient as for metallic systems, even for the smallest islands (of the order of 10 Pd atoms). The growth of the carbonyl-like compound proceeds via formation of Pd-Pd bonds and has a relatively well-defined local structure. It is demonstrated that the properties of this compound approach those of an extended system for increasing coverages, and it may therefore also serve as an important link between a carbonyl and CO adsorbed on a metallic surface. A brief discussion is also given in which the results are discussed in terms of electronic properties of the thin alumina film versus bulk alumina and the applicability of the former to the construction of model catalysts

Interaction of CO with Pd clusters supported on a thin alumina film

The adsorption of CO on Pd particles supported on a thin alumina film has been studied employing high resolution x‐ray photoelectron spectroscopy (XPS) and x‐ray absorption spectroscopy (XAS), and of special interest was the CO–Pd interaction as a function of island size and CO coverage. CO saturation at 90 K leads to an overlayer characterized by a rather weak CO–Pd hybridization as manifested by the core ionized and core excited states. The interaction strength gradually increases with island size. Desorption of parts of the overlayer results in CO more strongly interacting with the Pd islands. A comparison between the XPS and XAS energies yields a behavior indistinguishable from metallic systems for islands larger than 15 Å, i.e., the XPS binding energy appears near the x‐ray absorption onset. For the smallest islands (5 Å), a CO coverage dependent reversal of the XPS–XAS energy relation was observed, indicating a drastic change in the screening ability of the CO–Pd complex