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The economic and social well-being of citizens depends on the reliable functioning of critical infrastructures, and in particular, the provision of a reliable telecommunication system. Integrated risk and resilience analysis and improvement processes have been proposed and adopted to critical infrastructure systems. However, fast, tabular, and in operational contexts realizable implementations are still lacking. The paper proposes a set of interlinked tables for a fast, semi-quantitative implementation of such a process. The sequence and structure of the tables is chosen to capture the relevant input for the risk and resilience analysis and management process. Pulling from previous literature, four main constituents are identified and implemented as separate tables: system components, system functions, threats and mitigation options. The linkage between the tables and their contents, including minimum consistency requirements are expected to be sufficient for a successful implementation of the resilience analysis and management process. The linkage allows for direct computation of the correlations between the four constituents, e.g. system components with system functions, system functions with potential disruptions to identify critical combinations and threats with potential counter measures. Furthermore, quantification options and potential counter measures for the critical combinations can be inferred. Sample entries are given for the telecommunication infrastructure and the advantages of the approach are discussed.

Deep drilling of structural timber using ultra short pulse laser ablation is investigated directed towards using this for a novel approach for reinforcement and connection of structural timber. To gain a basic understanding of the interaction processes, the optical properties as well as the different abla-tion behavior of early and late wood are investigated and discussed. Based on these findings a hy-pothesis is formulated that directly links the local cell density with the ablation behavior of wood. Furthermore, deep drilling processes are successfully applied to structural timber despite inhomoge-neities of the material. We show that the damaging effects of the laser drilling on the mechanical properties of the realized screw connections is negligible.

High power ultrashort pulsed lasers are an ultimate manufacturing tool for a large variety of materials and provide outstanding properties for high precision manufacturing with almost no thermal effects and numerous new processing possibilities. However, using high power ultrashort pulsed lasers with high pulse repetition frequencies in the MHz region can cause thermal issues like overheating, melt generation and low ablation quality. High ablation quality only can be achieved, if all process parameters are carefully matched, which requires a deep understanding of the process, intensive simulation for selecting processing strategies and innovative system components. Beside ultra high speed scanning using polygon scanners the use of multiple laser beams provide the best and most versatile high power ablation solution. With switchable single beams using parallel acoustooptic and phase modulating beam steering systems together with diffractive optical beam splitter, high ablation rates can be achieved while maintaining the high processing quality. However, using multiple laser beams each single beam can influence the adjacent beam either by heat accumulation or by plasma and vapour emission. Distance of the single beams, pulse repetition frequency and scanning strategy have to be matched to the material and ablation geometry. With a careful adaption of all parameters highly accurate and fast processing can be achieved. With this approach a next step up to an all optical manufacturing system can be provided.

Ultrafast laser processing has shown its advantages characterized by a highly precise ablation with minimal thermal influence in many applications. Many investigations deal with the laser inherent parameters like pulse duration, repetition frequency and scan speed to describe their influence on the machining quality. However, the final machining quality is also determined by the initial surface morphology. To combine the conflicting objectives of productivity and quality a multi-level photonic process chain is established. For this kind of process chain, the knowledge about the influence of the respective surface morphology on the subsequent process step is of importance. For that reason the development of the surface morphology is investigated for several ultrafast laser parameter settings and initial surface morphologies. In our investigations, we were able to establish a mathematical model that describes the development of the roughness as a function of the ablation depth.

Francia, Bd. 33, Nr. 3 (2006)

Francia, Bd. 33, Nr. 3 (2006)

Francia, Bd. 33, Nr. 3 (2006)