1,892 research outputs found

    An assessment of skill needs in post-16 education and training

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    Can Intrusion Detection Implementation be Adapted to End-User Capabilities?

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    In an environment where technical solutions for securing networked systems are commonplace, there still exist problems in implementation of such solutions f or home and small business users. One component of this protection is the use of intrusion detection systems. Intrusion detection monitors network traffic for suspicious activity, performs access blocking and alerts the system administrator or user of potential attacks. This paper reviews the basic function of intrusion detection systems and maps them to an existing end-llser capability framework. Using this framework, implementation guidance and systematic improvement in implementation of this security measure are defined

    Chiral nanoemitter array: A launchpad for optical vortices

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    A chiral arrangement of molecular nanoemitters is shown to support delocalised exciton states whose spontaneous decay can generate optical vortex radiation. In contrast to techniques in which phase modification is imposed upon conventional optical beams, this exciton method enables radiation with a helical wave-front to be produced directly. To achieve this end, a number of important polarisation and symmetry-based criteria need to be satisfied. It emerges that the phase structure of the optical field produced by degenerate excitons in a propeller-shaped array can exhibit precisely the sought character of an optical vortex – one with unit topological charge. Practical considerations for the further development of this technique are discussed, and potential new applications are identified

    Optical instruments for measuring leaf area index in low vegetation : application in Arctic ecosystems

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    Author Posting. © Ecological Society of America, 2005. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 15 (2005): 1462–1470, doi:10.1890/03-5354.Leaf area index (LAI) is a powerful diagnostic of plant productivity. Despite the fact that many methods have been developed to quantify LAI, both directly and indirectly, leaf area index remains difficult to quantify accurately, owing to large spatial and temporal variability. The gap-fraction technique is widely used to estimate the LAI indirectly. However, for low-stature vegetation, the gap-fraction sensor either cannot get totally underneath the plant canopy, thereby missing part of the leaf area present, or is too close to the individual leaves of the canopy, which leads to a large distortion of the LAI estimate. We set out to develop a methodology for easy and accurate nondestructive assessment of the variability of LAI in low-stature vegetation. We developed and tested the methodology in an arctic landscape close to Abisko, Sweden. The LAI of arctic vegetation could be estimated accurately and rapidly by combining field measurements of canopy reflectance (NDVI) and light penetration through the canopy (gap-fraction analysis using a LI-COR LAI-2000). By combining the two methodologies, the limitations of each could be circumvented, and a significantly increased accuracy of the LAI estimates was obtained. The combination of an NDVI sensor for sparser vegetation and a LAI-2000 for denser vegetation could explain 81% of the variance of LAI measured by destructive harvest. We used the method to quantify the spatial variability and the associated uncertainty of leaf area index in a small catchment area.This research was funded by U.S. National Science Foundation grant DEB0087046

    Constructive or Disruptive? How Active Learning Environments Shape Instructional Decision-Making

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    This study examined instructional shifts associated with teaching in environments optimized for active learning, including how faculty made decisions about teaching and their perceptions of how students responded to those changes. The interviews and subsequent analysis reveal a broad range of course changes, from small modifications of existing activities to large shifts towards collaborative learning, many of which emerged during the term rather than being planned in advance. The faculty discuss several factors that influenced their decisions, including prior experience, professional identity, student engagement, and perceived and realized affordances of the environments