Erfassung der Rißbildung in Werkstoffen durch Ausnutzung der elektrischen Emission

A novel technique for detecting crack formation and propagation in metallic and nonmetallic materials, based upon electric emission, is described. It is shown that a correlation between electric emission and fracture exists for glass, steel and concretes. The superiority of the electric emission gauges when compared to other methods lies in the fact that a direct contact between the tested materials and the gauge is not required. Furthermore, the gauges are not destroyed by the fracture event and are, therefore, reusable so that multiple successive crack initiation and growth can be detected. Also, it is demonstrated that this technique is applicable to measurement of crack formation in other nonmetallic and even in conducting materials

Equality and fixpoints in the calculus of structures

International audienceThe standard proof theory for logics with equality and fixpoints suffers from limitations of the sequent calculus, where reasoning is separated from computational tasks such as unification or rewriting. We propose in this paper an extension of the calculus of structures, a deep inference formalism, that supports incremental and contextual reasoning with equality and fixpoints in the setting of linear logic. This system allows deductive and computational steps to mix freely in a continuum which integrates smoothly into the usual versatile rules of multiplicative-additive linear logic in deep inference

AlON: A brief history of its emergence and evolution

In the early 1970s in Japan, the United States and France it was found that additions of nitrogen into aluminum oxide resulted in new spinel-like phases. At about the same time there was much increased interest in oxynitrides, stimulated by Professor K. Jack in the UK and Y. Oyama in Japan. Following these activities a major research program in this area was initiated at the Army Materials and Mechanics Research Center in Watertown, Massachusetts in 1974. These efforts resulted in the first complete Al2O3-AIN phase equilibrium diagram and a process to reactively sinter to nearly full density, translucent aluminum oxynitride spinel ceramic, which was named AlON. Subsequently, the Raytheon Company further developed AlON into a highly transparent material (ALON (TM)) with many applications including transparent armor and EM domes and windows, among others-the technology was recently transferred to the Surmet Corporation. This paper will review the early history, phase equilibrium, crystal chemistry, and properties of this material, along with more recent work in our laboratory on transient liquid phase sintering and new data on lattice parameter measurements. In addition, recent results of collaborative work on AlON's dynamic mechanical properties using plate impact, Kolsky bar and edge-on impact (EoI) experimental techniques, including preliminary modeling at the microstructural scale of AlON in the EoI test, will be presented

On Combinatorial Proofs for Logics of Relevance and Entailment

International audienceHughes' combinatorial proofs give canonical representations for classical logic proofs. In this paper we characterize classical combi-natorial proofs which also represent valid proofs for relevant logic with and without the mingle axiom. Moreover, we extend our syntax in order to represent combinatorial proofs for the more restrictive framework of entailment logic