14,399 research outputs found

    Minimal kernels of Dirac operators along maps

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    Let MM be a closed spin manifold and let NN be a closed manifold. For maps f ⁣:MNf\colon M\to N and Riemannian metrics gg on MM and hh on NN, we consider the Dirac operator Dg,hfD^f_{g,h} of the twisted Dirac bundle ΣMRfTN\Sigma M\otimes_{\mathbb{R}} f^*TN. To this Dirac operator one can associate an index in KOdim(M)(pt)KO^{-dim(M)}(pt). If MM is 22-dimensional, one gets a lower bound for the dimension of the kernel of Dg,hfD^f_{g,h} out of this index. We investigate the question whether this lower bound is obtained for generic tupels (f,g,h)(f,g,h)

    Stand-alone flat-plate photovoltaic power systems: System sizing and life-cycle costing methodology for Federal agencies

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    A simple methodology to estimate photovoltaic system size and life-cycle costs in stand-alone applications is presented. It is designed to assist engineers at Government agencies in determining the feasibility of using small stand-alone photovoltaic systems to supply ac or dc power to the load. Photovoltaic system design considerations are presented as well as the equations for sizing the flat-plate array and the battery storage to meet the required load. Cost effectiveness of a candidate photovoltaic system is based on comparison with the life-cycle cost of alternative systems. Examples of alternative systems addressed are batteries, diesel generators, the utility grid, and other renewable energy systems

    Integrating Industry and National Economic Accounts: First Steps and Future Improvements

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    The integration of the annual I-O accounts with the GDP-by-industry accounts is the most recent in a series of improvements to the industry accounts provided by the BEA in recent years. BEA prepares two sets of national industry accounts: The I-O accounts, which consist of the benchmark I-O accounts and the annual I-O accounts, and the GDPby- industry accounts. Both the I-O accounts and the GDP-by-industry accounts present measures of gross output, intermediate inputs, and value added by industry. However, in the past, they were inconsistent because of the use of different methodologies, classification frameworks, and source data. The integration of these accounts eliminated these inconsistencies and improved the accuracy of both sets of accounts. The integration of the annual industry accounts represents a major advance in the timeliness, accuracy, and consistency of these accounts, and is a result of significant improvements in BEA's estimating methods. The paper describes the new methodology, and the future steps required to integrate the industry accounts with the NIPAs. The new methodology combines source data between the two industry accounts to improve accuracy; it prepares the newly integrated accounts within an I-O framework that balances and reconciles industry production with commodity usage. Moreover, the new methodology allows the acceleration of the release of the annual I-O accounts by 2 years and for the first time, provides a consistent time series of annual I-O accounts. Three appendices are provided: A description of the probability-based method to rank source data by quality; a description of the new balancing produced for producing the annual I-O accounts; and a description of the computation method used to estimate chaintype price and quantity indexes in the GDP-by-industry accounts.

    The Ever Changing Circumstellar Nebula Around UW Centauri

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    We present new images of the reflection nebula surrounding the R Coronae Borealis Star, UW Cen. This nebula, first detected in 1990, has changed its appearance significantly. At the estimated distance of UW Cen, this nebula is approximately 0.6 ly in radius so the nebula cannot have physically altered in only 8 years. Instead, the morphology of the nebula appears to change as different parts are illuminated by light from the central star modulated by shifting thick dust clouds near its surface. These dust clouds form and dissipate at irregular intervals causing the well-known declines in the R Coronae Borealis (RCB) stars. In this way, the central star acts like a lighthouse shining through holes in the dust clouds and lighting up different portions of the nebula. The existence of this nebula provides clues to the evolutionary history of RCB stars possibly linking them to the Planetary Nebulae and the final helium shell flash stars.Comment: To be published in ApJ Letters. 5 pages, 3 figures (2 in color

    Conceptualizing a Trauma Informed Child Welfare System for Indian Country

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    The creation of trauma-informed systems that use evidence-based, culturally competent interventions for affected children and families is a priority in Indian Country because mounting evidence from adverse childhood experiences research with American Indians documents the incidence and prevalence of trauma. What is more, an emergent line of research documents secondary traumatic stress (STS) in the adult workforce, which reduces their ability to help affected children and families and contributes to workforce turnover. The development of a trauma-informed system entails evidence-based detection, treatment, and prevention mechanisms for children, families, and STS-affected social services professionals. With tribal child welfare systems as a starting point and also as a centerpiece for the development of companion, trauma-informed behavioral and mental health systems, we propose a conceptual framework for such work to guide innovative system designs. Although some aspects of such a system currently are in place in several Native American communities, to our knowledge the comprehensive design we describe is not fully developed and implemented anywhere. Adaptive leadership and evaluation-driven, organizational learning systems are practical necessities

    A V-Diagram for the Design of Integrated Health Management for Unmanned Aerial Systems

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    Designing Integrated Vehicle Health Management (IVHM) for Unmanned Aerial Systems (UAS) is inherently complex. UAS are a system of systems (SoS) and IVHM is a product-service, thus the designer has to take into account many factors, such as: the design of the other systems of the UAS (e.g. engines, structure, communications), the split of functions between elements of the UAS, the intended operation/mission of the UAS, the cost verses benefit of monitoring a system/component/part, different techniques for monitoring the health of the UAS, optimizing the health of the fleet and not just the individual UAS, amongst others. The design of IVHM cannot sit alongside, or after, the design of UAS, but itself be integrated into the overall design to maximize IVHM’s potential. Many different methods exist to help design complex products and manage the process. One method used is the V-diagram which is based on three concepts: decomposition & definition; integration & testing; and verification & validation. This paper adapts the V-diagram so that it can be used for designing IVHM for UAS. The adapted v-diagram splits into different tracks for the different system elements of the UAS and responses to health states (decomposition and definition). These tracks are then combined into an overall IVHM provision for the UAS (integration and testing), which can be verified and validated. The stages of the adapted V-diagram can easily be aligned with the stages of the V-diagram being used to design the UAS bringing the design of the IVHM in step with the overall design process. The adapted V-diagram also allows the design IVHM for a UAS to be broken down in to smaller tasks which can be assigned to people/teams with the relevant competencies. The adapted V-diagram could also be used to design IVHM for other SoS and other vehicles or products

    Teaching sustainability and stewardship workshop 1: Collaborative approach to developing engagement with science and religion: Exploring sustainability in an international learning community

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    Workshop 1 introduces a collaborative approach to developing engagement with science and religion, by exploring sustainability in an international learning community of teachers based in Pakistan and England. The aim of the session was to begin to explore sustainability through science and religious worldviews. Participants were invited to: 1. Explore the meaning of the term ‘sustainability’ 2. Consider the relationship between science and religion 3. Reflect on the nature and communication of knowledge 4. Explore the Learning Community Blackboar
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