High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature

HARPS spectra with S/N > 600 for 21 solar twin stars are used to determine very precise (sigma ~ 0.01 dex) differential abundances of C, O, Na, Mg, Al, Si, S, Ca, Ti, Cr, Fe, Ni, Zn, and Y in order to see how well [X/Fe] is correlated with elemental condensation temperature, Tc. In addition, precise (sigma < 0.8 Gyr) stellar ages are obtained by interpolating between Yonsei-Yale isochrones in the logg - Teff diagram. It is confirmed that the ratio between refractory and volatile elements is lower in the Sun than in most of the solar twins, but for many stars, the relation between [X/Fe] and Tc is not well defined. For several elements there is, instead, an astonishingly tight correlation between [X/Fe] and stellar age with amplitudes up to 0.2 dex over an age interval of 8 Gyr in contrast to the lack of correlation between [Fe/H] and age. While [Mg/Fe] increases with age, the s-process element yttrium shows the opposite behavior so that [Y/Mg] can be used as a sensitive chronometer for Galactic evolution. [Na/Fe] and [Ni/Fe] are not well correlated with stellar age, but define a tight Ni-Na relation similar to that previously found for more metal-poor stars. These results provide new constraints on supernovae yields and Galactic evolution. Furthermore, it is found that the C/O ratio evolves very little with time, which is of interest for discussions of the composition of exoplanets.Comment: 13 pages, 14 figures, and 2 on-line tables. To appear in A&

Beyond electronic disintermediation through multi-agent systems

Supply chain management represents a critical competency in today's global business environment and has been the focus of considerable, but mixed, information systems research. The research described in this paper builds on work in multi-agent systems to argue that intelligent agents offer excellent potential and capability for supply chain management, and contributes to discussion and theory pertaining to electronic markets and supply chain disintermediation. Argues that the knowledge associated with intermediation work represents a key mediating variable between disintermediating technology and supply chain efficacy and discusses how intelligent agent technology can be employed to both intermediate and disintermediate the supply chain, attaining the cost and cycle-time benefits of disintermediation without the attendant loss of human knowledge and expertise. The paper outlines a number of implications for theory and practice in information systems, and it formalizes some important research questions through a contingency framework to help stimulate and guide future work along these lines

Toward enterprise process engineering: configuration measurement and analysis

The enterprise process has become a central unit of analysis in management. But a dearth of theory and methods to predict process performance is available to the enterprise manager. With the proposition that enterprise process design represents an engineering problem as much as a managerial one, we focus on the process configuration and measurement to overcome design limitations that currently confront the enterprise manager. Building on seminal work for process description and comparison, and employing Graph Theory and Measurement Theory, we integrate this work and demonstrate useful analytical properties associated with the kinds of measures proposed (e.g., ratio scales). This represents a new result, which extends the prior research on enterprise process design and makes a contribution to our understanding in management science. Further, with parallels to the predictive capability enjoyed by engineers who design physical artifacts, we indicate how enterprise process configuration measures can be used to hypothesize relations with respect to enterprise performance. And we suggest how enterprise managers may design processes in a deductive manner-working backward from performance requirements to determine configuration parameters required for designs to meet performance goals. These represent new ca abilities not previously available to the enterprise manager as well as another contribution of the resent research.Approved for public release; distribution is unlimited

A Computational Approach to Diagnosing Misfits, Inducing Requirements, and Delineating Transformations for Edge Organizations

Nominated for Best Paper Award

Toward an Operational Proxy for Acquisition Workforce Quality: Measuring Dynamic Knowledge and Performance at the Tactical Edges of Organizations

Naval Postgraduate School Acquisition Research Progra

Manned-Unmanned Teaming in Distributed Maritime Operations

NPS NRP Project PosterManned-Unmanned Teaming in Distributed Maritime OperationsN9 - Warfare SystemsThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

An Extended Model of Knowledge-Flow Dynamics

The modern enterprise depends upon timely and effective flows of knowledge through its organizations for success. But knowledge is not evenly distributed through the enterprise, and a dearth of information systems is available to enable such timely and effective flows. Further, the few theoretical knowledge-flow models available have not yet been developed to a point where they can effectively inform the design of information systems and business processes to support knowledge flow in the enterprise. A survey of current practice shows that such system and process design is accomplished principally by trial and error, one of the least effective approaches known. The research described in this article builds upon and extends current theory about knowledge flow. It focuses in particular on investigating flow dynamics to inform the design of information systems and business processes to enhance the flow of knowledge through the enterprise. Leveraging the good understanding of flows in other domains, we strive to extend theory that can lead to devices of considerable utility in the enterprise knowledge domain. The result is a four-dimensional, dynamic model that can be used to classify and visualize a diversity of knowledge-flow patterns through the enterprise. These patterns can, in turn, be analyzed to inform the design of useful information systems and business processes. The implications of this dynamic model are explored and a number of hypotheses are generated to motivate and guide future research into the phenomenology of knowledge flow