The construction of sword during the medieval age reaches a good level of quality in the western world where the "Damascus" swords assumes a legendary fame. Even from the ancient times two types of "Damascus" swords have been known: the eastern type based on the application of the ipereuctoid steels and the Western Damascus or Welded Damascus, because obtained through the friction welding of thin strips featured by different carbon contents. In this study a sword found in 1948 on the Adige riverside, near Legnago, has been sectioned and examined by optical microscopy, SEM-EDS, SEM-EBSD and the micro-hardness Vickers testing in order to point out the main microstructural features of the welded system, to identify the chemical composition of the non-metallic inclusions and the crystallographic textures produced by the forging operation. The obtained results have permitted to formulate plausible hypothesis about the significant aspects of the production process: temperature of the ore reducing furnace and of the thermo-mechanical route followed by the ancient artisans.

Abstract. In this work, a method for the stability analysis of wind turbines is described. A system identification technique, formulated for handling stochastic disturbances, is used to identify a periodic reduced order model from suitable recorded time histories of the system. Afterwards, such reduced model is analyzed according to Floquet theory. The formulation is model-independent, in the sense that it does not require knowledge of the equations of motion of the periodic system being analyzed, and it is applicable to an arbitrary number of blades and to any configuration of the machine. In addition, as wind turbulence can be viewed as a stochastic disturbance, the method is also applicable to real wind turbines operating in the field. The characteristics of the new method are verified first with a simplified analytical model, and then using a high-fidelity multibody model of a multi-MW wind turbine. Results are compared with those obtained by the well known operational modal analysis approach.

Minimizing the cost of energy of a wind farm is a difficult task, which involves reducing the wake effects while satisfying several constraints. Due to its multidisciplinary nature, this problem is usually solved through numerical optimisers. TOPFARM is one of these tools, and in this paper, we have added to it a constraint on the fatigue loads. The efficiency of the implementation is guaranteed by an extensive use of gradients and load surrogate models. The paper is concluded by showing some case studies.

This study aims at casting new light about the knowledge of the metallurgical techniques developed by the Etruscan and the Romans during their political and cultural interactions in Central Italy. The analysis of two weapons found at the Etruscan sites of Vetulonia and Chiusi have pointed out some new information about the production process performed. The optical microscopy analysis has allowed to identify the sequence of the microstructural constituents present in the two ancient weapons. SEM-EDS has permitted to identify the chemical composition of the non metallic inclusion and to estimate the average temperature of the reduction process. The analysis of the metal matrix performed by a coupled argon plasma spectrometer permitted to measure the average chemical compositions of the studied alloys. SEM-EBSD analysis has allowed to identify the crystallographic textures present within the different zones of the sword blades and this has indicated the realization of a forming process that gave interesting mechanical properties to the metal products. The results obtained by the Etruscans artisans were of very high standard quality and their production system had been certainly assimilated by the Romans who found in them a strategic factor to increase their power.

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