93-GT-300 CALIBRATING ULTRASONIC IMAGES FOR THE NDE OF STRUCTURAL MATERIALS

ABSTRACT Ultrasonic imaging is taking a larger and larger role in the NDE of turbine engine materials and in support of fracture mechanics calculations. It is also playing an increasing role in quality and process control

Advances in Transient-Liquid-Phase Bonding of Ultra-high Temperature ZrC Ceramics

AbstractFull exploitation of the many attractive engineering properties of ultra-high temperature ceramics (UHTCs) requires that they can be joined. This paper explores progress in identifying joining strategies based on the use of transient liquid phases (TLPs). Wetting studies are used to explore the suitability of specific liquids for joining, while bonding studies provide the ultimate test. Sintering aids in the UHTC provide a major potential obstacle to successful joining, and dissolved impurities in the TLP can also complicate the joining process. Nonetheless, we show that well-bonding interfaces can be achieved when ZrC ceramics are bonded at 1673 K using a Ni/Nb/Ni multilayer interlayer

Individualization as driving force of clustering phenomena in humans

One of the most intriguing dynamics in biological systems is the emergence of clustering, the self-organization into separated agglomerations of individuals. Several theories have been developed to explain clustering in, for instance, multi-cellular organisms, ant colonies, bee hives, flocks of birds, schools of fish, and animal herds. A persistent puzzle, however, is clustering of opinions in human populations. The puzzle is particularly pressing if opinions vary continuously, such as the degree to which citizens are in favor of or against a vaccination program. Existing opinion formation models suggest that "monoculture" is unavoidable in the long run, unless subsets of the population are perfectly separated from each other. Yet, social diversity is a robust empirical phenomenon, although perfect separation is hardly possible in an increasingly connected world. Considering randomness did not overcome the theoretical shortcomings so far. Small perturbations of individual opinions trigger social influence cascades that inevitably lead to monoculture, while larger noise disrupts opinion clusters and results in rampant individualism without any social structure. Our solution of the puzzle builds on recent empirical research, combining the integrative tendencies of social influence with the disintegrative effects of individualization. A key element of the new computational model is an adaptive kind of noise. We conduct simulation experiments to demonstrate that with this kind of noise, a third phase besides individualism and monoculture becomes possible, characterized by the formation of metastable clusters with diversity between and consensus within clusters. When clusters are small, individualization tendencies are too weak to prohibit a fusion of clusters. When clusters grow too large, however, individualization increases in strength, which promotes their splitting.Comment: 12 pages, 4 figure