Ultrasonic Samples Using Diffusion Bonding Techniques

The objective of this part of the ARPA/AFML program was to produce a set of standard samples which would be suitable for NDE testing and characterization of different NDE techniques. The idea was to have a standard set of samples that could be used to compare results of various investigators and various techniques. In addition to internal defects it was decided, that in order to couple the previous work, the standard flat bottom hole type of defect should also be produced and so we have done this

An Econometric Analysis of Trends in Research Joint Venture Activity.

Edith Penrose was one of the first scholars to point out that firms may need to rely on research joint ventures (RJVs) to acquire access to resources that can help them achieve and sustain a competitive advantage. We estimate an econometric model of the propensity of firms to disclose their intension to engage in RJVs, in order to explain the recent precipitous decline in RJVs filed with the U.S. Department of Justice. We find that RJV activity is inversely related to the competitive position of U.S. firms in global high-technology industries and that the establishment of the U.S. Commerce Department's Advanced Technology Program (ATP) induced a structural change in the propensity of firms to engage in RJVs. Thus, two factors may explain the recent downturn in RJV filings: a substantial improvement in U.S. global performance in high-technology markets and a sharp decline in ATP funding.

Shear bands and cracking of metallic glass plates in bending

The thickness dependence of yielding and fracture of metallic glass plates subjected to bending is considered in terms of the shear band processes responsible for these properties. We argue that the shear band spacing (and length) scales with the thickness of the plate because of strain relaxation in the vicinity of the shear band at the surface. This is consistent with recent measurements of shear band spacing versus sample size. We also argue that the shear displacements in the shear band scale with the shear band length and plate thickness, thus causing cracks to be initiated in thicker plates at smaller bending strains. This leads to fracture bending strains that decrease markedly with increasing plate thickness, consistent with recent experiments. These results suggest that amorphous metals in the form of foams might have superior ductility and toughness

Evolution of foot-and-mouth disease virus intra-sample sequence diversity during serial transmission in bovine hosts

RNA virus populations within samples are highly heterogeneous, containing a large number of minority sequence variants which can potentially be transmitted to other susceptible hosts. Consequently, consensus genome sequences provide an incomplete picture of the within- and between-host viral evolutionary dynamics during transmission. Foot-and-mouth disease virus (FMDV) is an RNA virus that can spread from primary sites of replication, via the systemic circulation, to found distinct sites of local infection at epithelial surfaces. Viral evolution in these different tissues occurs independently, each of them potentially providing a source of virus to seed subsequent transmission events. This study employed the Illumina Genome Analyzer platform to sequence 18 FMDV samples collected from a chain of sequentially infected cattle. These data generated snap-shots of the evolving viral population structures within different animals and tissues. Analyses of the mutation spectra revealed polymorphisms at frequencies >0.5% at between 21 and 146 sites across the genome for these samples, while 13 sites acquired mutations in excess of consensus frequency (50%). Analysis of polymorphism frequency revealed that a number of minority variants were transmitted during host-to-host infection events, while the size of the intra-host founder populations appeared to be smaller. These data indicate that viral population complexity is influenced by small intra-host bottlenecks and relatively large inter-host bottlenecks. The dynamics of minority variants are consistent with the actions of genetic drift rather than strong selection. These results provide novel insights into the evolution of FMDV that can be applied to reconstruct both intra- and inter-host transmission routes

Gathering experience in trust-based interactions

As advances in mobile and embedded technologies coupled with progress in adhoc networking fuel the shift towards ubiquitous computing systems it is becoming increasingly clear that security is a major concern. While this is true of all computing paradigms, the characteristics of ubiquitous systems amplify this concern by promoting spontaneous interaction between diverse heterogeneous entities across administrative boundaries [5]. Entities cannot therefore rely on a specific control authority and will have no global view of the state of the system. To facilitate collaboration with unfamiliar counterparts therefore requires that an entity takes a proactive approach to self-protection. We conjecture that trust management is the best way to provide support for such self-protection measures

New Ultrasonic Standards

Standard samples containing defects of known size, shape, and· location are requirements for the evaluation and calibration of NDE test equipment. Here we review the methods developed f~r producing such samples from selected metallic alloys and ceramics. In the work with metallic alloys, the method of diffusion bonding Ti-6Al-4V is presented in some detail and is illustrated for a large number of samples containing a variety of defects ranging from spherical cavities and inclusions, to prolate and oblate spheroids, to thin discs and simulated cracks. In the work with ceramics, the method of hot pressing of glasses with cavities and inclusions is illustrated for a variety of defects. The presentation demonstrates how these samples may be applied in a procedure for calibrating ultrasonic systems by employing a recently proposed characteristic equation for the system and a figure-of-merit for the transducers in analogy to the gain of a radar antenna

The effects of leader succession and prior leader experience on postsuccession organizational performance

In this article we strive to reconcile equivocal findings about the effects of top leader succession and prior leadership experience on postsuccession organizational performance. In doing so, we draw on insights from theories of human capital, learning, and asymmetric information to better understand the conditions under which leaders increase or decrease postsuccession performance. Employing a sample of 119 newly appointed leaders in the English Premier League (1996–2010), we find the following results. First, relating to the succession event, outside leaders that directly move between leadership positions are associated with higher postsuccession performance while the departure of a prior leader to a leadership position in another organization has a negative effect on postsuccession performance. Second, relating to prior leadership experience, leaders with domestic top leader experience are associated with lower postsuccession performance, while leaders with foreign top leader experience are associated with higher postsuccession performance