Modelling Decarburization in Electrical Steels

A model is presented to predict the decarburization rate of electrical steels during reactive annealing. In a first step, the warm annealing atmosphere composition is calculated as function of the composition of the cold gas containing N₂‐H₂‐H₂O‐CO‐CO₂‐CH₄‐O₂. In a second step, the decarburization kinetics, which is controlled both by the surface reaction and by the diffusion of carbon towards the surface, is calculated. The model is then used to study the balance between surface reaction and the diffusion control of the decarburization process. We could conclude that for low sheet thickness and/or low H₂O/H₂ ratio in the annealing atmosphere, the decarburization is surface reaction controlled, while for commercial thicknesses and industrially applied dew points, the process is diffusion controlled. Furthermore, we looked at the difference in decarburization between complex N₂‐H₂‐H₂O‐CO‐CO₂ atmospheres used in industrial application, and N₂‐H₂‐H₂O atmospheres typically used in lab annealing. We could conclude that the decarburization rate is influenced by the addition of CO and CO₂ and that the final carbon level is increased if CO and CO₂ are added to the gas.     

On the security of fair non-repudiation protocols

We analyzed two non-repudiation protocols and found some new attacks on the fairness and termination property of these protocols. Our attacks are enabled by several inherent design weaknesses, which also apply to other non-repudiation protocols. To prevent these attacks, we propose generic countermeasures that considerably strengthen the design and implementation of non-repudiation protocols. The application of these countermeasures is finally shown by our construction of a new fair non-repudiation protocol.     

Asymptotic behavior and inverse problem in layered scattering media

The main challenge of noninvasive optical biopsy is to obtain an accurate value of the optical coefficients of an encapsulated organ (muscle, brain, etc.). The idea developed by us is that some interesting information could be deduced from the long-time behavior of the reflectance function. This asymptotic behavior is analyzed for layered media in the framework of the diffusion approximation. A new method is derived to obtain accurate values for the optical parameters of the deepest layers. This method is designed to work in a specific long-time regime that is still within the scope of standard time-of-flight experiments but far from being included in the mathematically defined asymptotic region. The limits of this method, linked to the cases where the asymptotic behavior is no longer governed by the deepest layer, are then discussed.     

Analysis of e-commerce protocols: Adapting a traditional technique

We present the adaptation of our model for the validation of key distribution and authentication protocols to address some of the specific needs of protocols for electronic commerce. The two models defer in both the threat scenario and in the protocol formalization. We demonstrate the suitability of our adaptation by analyzing a specific version of the Internet Billing Server protocol introduced by Carnegie Mellon University. Our analysis shows that, while the security properties a key distribution or authentication protocol shall provide are well understood, it is often not clear which properties an electronic commerce protocol can or shall provide. We use the automatic theorem proving software Otter developed at Argonne National Laboratories for state space exploration.     

Unraveling the Morphology-Function Correlation of Mesoporous ZnO Films upon Water Exposure

Ubiquitous moisture in synthetic conditions and ambient environments can strongly influence the conductivity of ZnO semiconductors via the chemisorption and physisorption of water molecules on the ZnO surface. Such an intrinsically water-sensitive nature will become more evident in mesoporous ZnO films where a large surface area and active sites are created simultaneously. However, fundamental insights underlying water-mediated ZnO surface chemistry and electrical conductivity and the factors affecting them remain ambiguous due to the complexity of ZnO surfaces and the difficulties of in situ characterizations at multi-dimensions. Here, self-assembling diblock copolymers are exploited as structure-directing agents to achieve mesoporous ZnO thin films with highly tailorable structural characteristics ranging from nanomorphologies, over crystalline levels, to defect contents. As verified by theoretical calculations, the presence of oxygen vacancy will facilitate favorable water adsorption and subsequent dissociation on the polar ZnO surfaces. Upon humidity exposure with progressively increased levels, mesoporous ZnO films are revealed to follow an almost positive relationship between adsorption and electrical conductivity but show superior morphological stability. This work not only elucidates the water-governed ZnO surface chemistry but may also promote a comprehensive understanding of the morphology-function relationship on ZnO-based electronics.     

Detection of sul1, sul2 and sul3 in sulphonamide resistant Escherichia coli isolates obtained from healthy humans, pork and pigs in Denmark

The occurrence of sulphonamide resistance was investigated in 998 Escherichia coli isolates, obtained from pig faeces collected at slaughter, Danish pork collected at retail outlets and from faeces from healthy persons in Denmark. In total 18% (n=35), 20% (n=38) and 26% (n=161) of the E. coli isolates obtained from humans, pork and pigs, respectively, were resistant to sulphonamide. All sulphonamide resistant E. coli isolates were investigated for the presence of sul1, sul2, sul3 and intI1 genes by PCR. The sul1 gene was detected in 40% (n=14), 29% (n=11) and 55% (n=88) of the sulphonamide resistant isolates from humans, pork and pigs, respectively. The sul2 gene was detected in 80% (n=28), 76% (n=29) and 50% (n=81) of isolates from humans, pork and pigs, respectively. None of the human isolates were PCR-positive for sul3, whereas sul3 was present in 5% of the pork isolates and 11% of the pig isolates. Of the 113 sul1 positive isolates, 97 carried the integron-associated integrase gene intI1. All 20 sul3 positive isolates were positive for intI1, and in 12 of these isolates sul3 was the only sulphonamide resistance gene detected. The origin of sul1 and sul2 found in isolates from healthy humans is speculative, but their spread from pigs to humans via the food chain is possible.     

Ultradisperse diamond cluster aggregation studied by atomic force microscopy

The structure of ultradisperse diamond (UDD) conglomerates was studied by scanning atomic-force microscopy (AFM). The UDD layers were prepared from a detonation carbon obtained by synthesis in an aqueous medium. The finest details in the AFM images of UDD layers are of the order of 10 nm, which does not allow individual 4.5-nm diamond clusters to be distinguished. The UDD conglomerates deposited and dried on a silicon substrate surface, exhibit certain deformation and differ from the initial (apparently, spherical) shape. This may imply that cohesion between the UDD nanoparticles is comparable with their adhesion to the silicon substrate.     

3d-Gis for Urban Purposes

New developments in urban planning, especially in environmentally oriented analysis including noise, air pollution, urban climate etc., call for new demands on authorities and planners. Due to the increasing availability of informations systems and of 3D-data, planners and municipalities emphasize modeling the urban space in three dimensions. While the visualization aspect is often and detailed considered, only a few investigations about interactive aspects on urban planning are available. In this paper we present a framework for a 3D-urban-GIS. This includes conceptual aspects and a first outline and implementation of an application prototype. For this representation, new scopes have to be considered from data acquisition to modeling and to storage. First, the urban object space is classified in an hierarchical 3D object structure. In accordance to different planning levels (i.e., levels-of-detail), several data acquisition methods are fused to obtain 3D datasets. The results show that a context specific methodology has to be defined. This includes planning aspects that are traditionally not available in GIS. Based on test sites in Rostock and Stuttgart, a 3D-urban-GIS prototype is in development, joining aspects of a 3D-visualization interface and a database for 3D objects.