4,480 research outputs found

    Optimized Anisotropic Rotational Invariant Diffusion Scheme on Cone-Beam CT

    Get PDF
    Cone-beam computed tomography (CBCT) is an important image modality for dental surgery planning, with high resolution images at a relative low radiation dose. In these scans the mandibular canal is hardly visible, this is a problem for implant surgery planning. We use anisotropic diffusion filtering to remove noise and enhance the mandibular canal in CBCT scans. For the diffusion tensor we use hybrid diffusion with a continuous switch (HDCS), suitable for filtering both tubular as planar image structures. We focus in this paper on the diffusion discretization schemes. The standard scheme shows good isotropic filtering behavior but is not rotational invariant, the diffusion scheme of Weickert is rotational invariant but suffers from checkerboard artifacts. We introduce a new scheme, in which we numerically optimize the image derivatives. This scheme is rotational invariant and shows good isotropic filtering properties on both synthetic as real CBCT data

    Automated ice-core layer-counting with strong univariate signals

    Get PDF
    We present an automated process for determining the annual layer chronology of an ice-core with a strong annual signal, utilising the hydrogen peroxide record from an Antarctic Peninsula ice-core as a test signal on which to count annual cycles and explain the methods. The signal is de-trended and normalised before being split into sections with a deterministic cycle count and those that need more attention. Possible reconstructions for the uncertain sections are determined which could be used as a visual aid for manual counting, and a simple method for assigning probability measures to each reconstruction is discussed. The robustness of this process is explored by applying it to versions of two different chemistry signals from the same stretch of the NGRIP (North Greenland Ice Core Project) ice-core, which shows more variation in annual layer thickness, with and without thinning to mimic poorer quality data. An adapted version of these methods is applied to the more challenging non-sea-salt sulphur signal from the same Antarctic Peninsula core from which the hydrogen peroxide signal was taken. These methods could readily be adapted for use on much longer datasets, thereby reducing manual effort and providing a robust automated layer-counting methodology

    Experiments in the automatic marking of ER-Diagrams

    Get PDF
    In this paper we present an approach to the computer understanding of diagrams and show how it can be successfully applied to the automatic marking (grading) of student attempts at drawing entity-relationship (ER) diagrams. The automatic marker has been incorporated into a revision tool to enable students to practice diagramming and obtain feedback on their attempts

    Using patterns in the automatic marking of ER-Diagrams

    Get PDF
    This paper illustrates how the notion of pattern can be used in the automatic analysis and synthesis of diagrams, applied particularly to the automatic marking of ER-diagrams. The paper describes how diagram patterns fit into a general framework for diagram interpretation and provides examples of how patterns can be exploited in other fields. Diagram patterns are defined and specified within the area of ER-diagrams. The paper also shows how patterns are being exploited in a revision tool for understanding ER-diagrams

    Environmental aspects of tensile membrane enclosed spaces

    Get PDF
    Buildings enclosed by fabric membranes are very sensitive to changes in environmental conditions as a result of their low mass and low thermal insulation values. Development in material technology and the understanding of the structural behaviour of tensile membrane structures along with the vast progress in computer formfinding software, has made it possible for structural design of tensile membrane structures to be approached with almost total confidence. On the contrary, understanding of the environmental behaviour in the spaces enclosed by fabric membrane and their thermal performance is still in its infancy, which to some extent has hindered their wide acceptance by the building industry. The environmental behaviour of tensile membrane structures is outlined and the possible use of the fabricā€™s topology and geometry particularly to enhance ventilation rates and airflow velocities within the enclosed space is discussed. A need for further research in this area is identified in order to fully realise the potential benefits offered by these structures

    Assessing the distributional impact of technical change in livestock and grains production in developing countriesĀ 

    Get PDF
    This paper outlines a general framework for analysing the distributional impact of commodity and factor price changes on the welfare of disaggregate households. The impact may be decomposed into an average effect and the departures from that average. The latter departures may be attributed to interactions between the commodity price changes and differences in consumption shares, on the one hand, and interactions between factor price changes and differences in factor earnings shares, on the other hand. Differences in consumption shares across households are estimated at the quintile level, using the International Comparisons Project (ICP) database in conjunction with the Deninger Squire database on income distribution. Estimated differences in factor income shares are obtained by combining information on total factor earnings, with observations on income by quintile, and initial estimates of the factor earnings pattern by quintile. Regional price impacts of technological change are estimated using the Global Trade Analysis Project (GTAP) model of global trade. We find that, in the case of Korea, Sri Lanka and Zambia, technological change in grains benefits the poorest house- holds relatively more than a comparable improvement in livestock productivity. The opposite is true in Thailand. With the exception of the Zambia livestock sector, technical progress in either livestock or grains benefits poorer households relatively more than their wealthier counterparts. While this stems primarily from their larger food consumption share, improvements in unskilled wages also play a role

    IJED support for eating disorders research in the time of COVIDā€19

    Get PDF
    This editorial reports on an anonymous survey question posed to eating disorders researchers about changes the International Journal of Eating Disorders (IJED) should implement to support the eating disorders research community affected by COVIDā€19. The editorial accompanies an IJED article that details responses to the larger survey focusing more broadly on COVIDā€19ā€related research disruptions. Survey invitations were sent to editorial board members of eating disorders journals, members of eating disorder scientific organizations (e.g., Eating Disorders Research Society), and individuals who provided at least three IJED reviews in the prior 12ā€‰months. We reviewed the responses of 187 participants and identified three categories of changes that: (a) had already been implemented by the journal, (b) cannot be implemented because they fall outside the scope of IJED, or (c) will be implemented in coming weeks or months. The latter category includes publishing topical COVIDā€19 papers, making some COVIDā€19ā€related content available open access, revising statistical guidelines, and issuing author guidance on reporting protocol changes caused by COVIDā€19ā€related disruptions. IJED recognizes the disruptive impacts that COVIDā€19 has on all activities in our field, including clinical work, teaching, and advocacy, and is committed to supporting authors during this difficult time while striving to publish highā€quality research
    • ā€¦
    corecore