Laser Generation of Sub-Micrometer Wrinkles in a Chalcogenide Glass Film as Physical Unclonable Functions

Laser interaction with solids is routinely used for functionalizing materials' surfaces. In most cases, the generation of patterns/structures is the key feature to endow materials with specific properties like hardening, superhydrophobicity, plasmonic color-enhancement, or dedicated functions like anti-counterfeiting tags. A way to generate random patterns, by means of generation of wrinkles on surfaces resulting from laser melting of amorphous Ge-based chalcogenide thin films, is presented. These patterns, similar to fingerprints, are modulations of the surface height by a few tens of nanometers with a sub-micrometer periodicity. It is shown that the patterns' spatial frequency depends on the melted layer thickness, which can be tuned by varying the impinging laser fluence. The randomness of these patterns makes them an excellent candidate for the generation of physical unclonable function tags (PUF-tags) for anti-counterfeiting applications. Two specific ways are tested to identify the obtained PUF-tag: cross-correlation procedure or using a neural network. In both cases, it is demonstrated that the PUF-tag can be compared to a reference image (PUF-key) and identified with a high recognition ratio on most real application conditions. This paves the way to straightforward non-deterministic PUF-tag generation dedicated to small sensitive parts such as, for example, electronic devices/components, jewelry, or watchmak.     

Communicating in Dynamic Conditions: How Do On-Site Construction Project Managers Do It?

A great many of today’s construction projects are characterized by high levels of dynamics, namely, the combined effect of complexity, uncertainty, and speed. Managing projects under such conditions is difficult and challenging, and the question is asked: How do managers do it? Aspiring to answer this question, ten excellent on-site construction project managers were systematically observed during one workweek each, within an extensive study that examined their performance in their dynamic management environments. The structured observation and documentation and the analysis that followed them enabled us to characterize the managers’ work and exposed their unique modes of operation through which they consistently excel in their work. Among many aspects addressed by the said study, this paper focuses on communication and, using various measures, examines the intensiveness and extensiveness of communication performed by the PMs in the broad context of their work. The study found that the on-site construction PMs were strongly oriented toward verbal communication of information (during nearly 80% of their activities and time); they spent a major portion of their workdays in meetings (during 60% of their activities, and of which nearly 80% were unplanned); and they showed clear preference for interacting informally with no more than one or two other persons (during 93% of their activities and 88% of the time). The unique knowledge base resulting from this study constitutes a potential contribution for practitioners who are required to function in similar dynamic work environments, as well as for students, teachers, and researchers of construction management.     

On the relative rate of hydrolysis of a series of ketals and their proton affinities

The relative rates of hydrolysis of a series of cyclic and acyclic ketals was studied. Their reactivity toward acid hydrolysis is explained by considering the ease of protonation and the cleavage of the C—O bond. The experimental work and the theoretical calculations of the proton affinities of the ketals suggest that the rate-limiting step of hydrolysis of ketals is a concerted protonation and cleavage of the C—O bond. The relative proton affinity is considered to be a direct consequence of the ease of proper lone pair orbital alignment on the oxygen atoms of the various ketals.