575 research outputs found

    The Coronal Analysis of SHocks and Waves (CASHeW) Framework

    Full text link
    Coronal Bright Fronts (CBF) are large-scale wavelike disturbances in the solar corona, related to solar eruptions. They are observed in extreme ultraviolet (EUV) light as transient bright fronts of finite width, propagating away from the eruption source. Recent studies of individual solar eruptive events have used EUV observations of CBFs and metric radio type II burst observations to show the intimate connection between low coronal waves and coronal mass ejection (CME)-driven shocks. EUV imaging with the Atmospheric Imaging Assembly(AIA) instrument on the Solar Dynamics Observatory (SDO) has proven particularly useful for detecting CBFs, which, combined with radio and in situ observations, holds great promise for early CME-driven shock characterization capability. This characterization can further be automated, and related to models of particle acceleration to produce estimates of particle fluxes in the corona and in the near Earth environment early in events. We present a framework for the Coronal Analysis of SHocks and Waves (CASHeW). It combines analysis of NASA Heliophysics System Observatory data products and relevant data-driven models, into an automated system for the characterization of off-limb coronal waves and shocks and the evaluation of their capability to accelerate solar energetic particles (SEPs). The system utilizes EUV observations and models written in the Interactive Data Language (IDL). In addition, it leverages analysis tools from the SolarSoft package of libraries, as well as third party libraries. We have tested the CASHeW framework on a representative list of coronal bright front events. Here we present its features, as well as initial results. With this framework, we hope to contribute to the overall understanding of coronal shock waves, their importance for energetic particle acceleration, as well as to the better ability to forecast SEP events fluxes.Comment: Accepted for publication in the Journal of Space Weather and Space Climate (SWSC

    CerealsDB 3.0:Expansion of resources and data integration

    Get PDF
    BACKGROUND: The increase in human populations around the world has put pressure on resources, and as a consequence food security has become an important challenge for the 21st century. Wheat (Triticum aestivum) is one of the most important crops in human and livestock diets, and the development of wheat varieties that produce higher yields, combined with increased resistance to pests and resilience to changes in climate, has meant that wheat breeding has become an important focus of scientific research. In an attempt to facilitate these improvements in wheat, plant breeders have employed molecular tools to help them identify genes for important agronomic traits that can be bred into new varieties. Modern molecular techniques have ensured that the rapid and inexpensive characterisation of SNP markers and their validation with modern genotyping methods has produced a valuable resource that can be used in marker assisted selection. CerealsDB was created as a means of quickly disseminating this information to breeders and researchers around the globe. DESCRIPTION: CerealsDB version 3.0 is an online resource that contains a wide range of genomic datasets for wheat that will assist plant breeders and scientists to select the most appropriate markers for use in marker assisted selection. CerealsDB includes a database which currently contains in excess of a million putative varietal SNPs, of which several hundreds of thousands have been experimentally validated. In addition, CerealsDB also contains new data on functional SNPs predicted to have a major effect on protein function and we have constructed a web service to encourage data integration and high-throughput programmatic access. CONCLUSION: CerealsDB is an open access website that hosts information on SNPs that are considered useful for both plant breeders and research scientists. The recent inclusion of web services designed to federate genomic data resources allows the information on CerealsDB to be more fully integrated with the WheatIS network and other biological databases. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12859-016-1139-x) contains supplementary material, which is available to authorized users

    Finite similitude in fracture mechanics

    Get PDF
    Scaled experimentation can potentially provide significant benefits such as reduced costs materials and time in testing but is afflicted by the phenomena of scale effects, where the behaviour at scale can be markedly different to that at full size. The design of scaled experiments is presently predominantly founded on the theory of dimensional analysis, which itself is grounded on the invariance of dimensionless governing equations with scale. The reality of fracture mechanics however is not invariant equations, but significant deviations and it is evident that scaled-fracture related experiments are presently limited by this affliction. This paper examines an advance in a new approach to scaled experimentation called finite similitude. The key question addressed here is whether it is possible to overcome the affliction of scale effects by performing not one but two scaled experiments at different scales. It is shown that finite similitude (unlike dimensional analysis) is able to capture all forms of scale dependency, which opens up the possibility of selecting alternative forms of scale invariance and consequently alternative forms of similitude. First-order finite similitude is investigated in the paper and applied to cracked compact-tension and three-point bending test specimens along with a cracked pressure vessel to illustrate the new concepts. These case studies reveal the veracity and potential of the new approach and highlight possibilities that hitherto would have been deemed impossible with the circumvention of scale effects (as traditionally defined).</p

    Application of first-order finite similitude in structural mechanics and earthquake engineering

    Get PDF
    An important experimental approach for the testing of earthquake-resistant structures is scaled experimentation with experimental designs impacted upon by the similitude theory of dimensional analysis. Unfortunately, the type of similitude provided by dimensional analysis seldom applies to complex structures, which is particularly problematic when scaling ratios are large. The issue is one of scale effects where the behaviour of the scaled version of any full-size structure can be markedly different. Recently however a new theory of scaling called finite similitude has emerged in the open literature that confirms that the similitude offered by dimensional analysis is just one of a countable infinite number of alternative possibilities. The new theory of scaling raises the possibility that buildings and structures can be designed and tested in new ways and this aspect is the focus of this paper. Similitude rules for single and two scaled experiments are examined to illustrate the benefits provided by alternative forms of similitude. The two types of similitude examined are termed zeroth order and first order finite similitude, which are shown to be two forms in an infinite number of alternative possibilities efficiently defined using a recursive relationship. The theory of scaling is founded on the metaphysical concept of space scaling yet provides the means to establish all scale dependencies for structural components and high-rise steel buildings along with buildings equipped with nonlinear-fluid viscous dampers for resisting earthquake loading conditions. It is shown through case-studies of increasing complexity how the new theory can be applied to reconstruct full-scale behaviours but also revealed are some of the limitations of the new approach.</p

    The theory of scaled electromagnetism

    Get PDF
    Scaled experimentation is an important experimental approach but is known to be limited by scale effects, which have the undesirable effect of changing the behaviour of a system with scale. Such behavioural changes with scale can on occasions be so marked as to make a scaled experiment almost worthless. Until very recently, there has been no universal solution to this problem with most scaled experiments founded on dimensional analysis and modified necessarily with ad hoc scaling rules. This article is concerned with the development and the application of a new approach to scaled experimentation called finite similitude for electro-magnetic systems. It is shown how the finite similitude theory can be applied to electromagnetism and the governing Maxwell equations in their macroscopic form. The ability of the theory to account for scale dependencies is investigated to reveal the benefits of performing two scaled experiments in describing system behaviour.</jats:p

    Empirical Analysis and Modelling of Information and Communications Technology in Agriculture for Southern Ontario, Canada

    Get PDF
    Information and communications technology (ICT) represents an important enabling technology for on-farm operations that helps to maximise yield and minimise on-farm inputs. This study investigates the adoption factors and coverage characteristics of ICT in Southern Ontario. A set of eight site and situation adoption factors were identified explaining 57% of the variation in agricultural high-speed Internet utilisation for Southern Ontario. ICT coverage was assessed through service carrier and band factors, and their presence in rural settlements. Findings of the research indicate that there exists a digital divide among settlements in Southern Ontario and recommendations for targeted policy and investment in infrastructure are proposed to bridge the gap

    The breaking of geometric similarity

    Get PDF
    Scaled experimentation plays an important role in prototype and process development but is recognised to be severely constrained by the need for similitude, founded on the concepts of geometric, kinematic and kinetic similarity. This paper examines the possibility of breaking the requirement for geometric similarity by introducing the law of finite similitude for anisotropic scaling, which applies to continuum mechanics on anisotropically-scaled spaces. The law confirms that similarity solutions on skewed spaces always exist separately for quasistatic deformational and thermal-continuum problems. Thermomechanical and continuum dynamic problems however are shown to suffer from the inclusion of a (non-physical) non-orthogonal metric arising from the skewed coordinate system associated with anisotropic-space scaling. Even in this case however, an important subclass of problems is shown to be physically realisable involving a dominant component of velocity (displacement), where geometric similarity can again be broken yet retain good accuracy. The ability to skew artefacts yet achieve similitude is recognised to be a particularly important outcome as it allows for example one experimental model to be used to predict the behaviour of multiple skewed models. To showcase and highlight the significance of the new concept various scaled numerical models with anisotropic scaling with different geometrical scaling ratios in different directions is considered. The applicability of the theory is tested on a number of case studies providing strong supporting evidence for the validity and applicability of the new theory.</p

    High resolution synchrotron imaging of wheat root hairs growing in soil and image based modelling of phosphate uptake

    No full text
    Root hairs are known to be highly important for uptake of sparingly soluble nutrients, particularly in nutrient deficient soils. Development of increasingly sophisticated mathematical models has allowed uptake characteristics to be quantified. However, modelling has been constrained by a lack of methods for imaging live root hairs growing in real soils.We developed a plant growth protocol and used Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) to uncover the 3D interactions of root hairs in real soil. We developed a model of phosphate uptake by root hairs based directly on the geometry of hairs and associated soil pores as revealed by imaging.Previous modelling studies found that root hairs dominate phosphate uptake. By contrast, our study suggests that hairs and roots contribute equally. We show that uptake by hairs is more localised than by roots and strongly dependent on root hair and aggregate orientation.The ability to image hair-soil interactions enables a step change in modelling approaches, allowing a more realistic treatment of processes at the scale of individual root hairs in soil pores

    A Finite Similitude Approach to Scaled Impact Mechanics

    Get PDF
    The response characteristics of large-scale structures subjected to impact loading can in principle be determined by scaled experiments. Unfortunately, scaling suffers from scale effects and for impact mechanics, the non-scalability of strain rate and strain hardening can diminish the effectiveness of scaled trials. To resolve this difficulty, a new scaling method has recently appeared in the open literature called finite similitude. The theory is founded on the metaphysical concept of space scaling, where the idea is that by expanding or contracting space, changes in the governing mechanics can be assessed. In this paper the finite-similitude theory is further developed, where it is demonstrated how the constraints imposed by dimensional analysis can be broken. A new form of similarity is introduced but at the cost of requiring two scaled experiments at distinct scales. It is shown however, how the theory is able to combine the information from the two scaled trials to predict outcomes that can be markedly superior to what can be achieved with experiments at a single scale. All scale dependencies are accounted by the theory and consequently the new formulation attempts to capture scale effects, so provides a more realistic approach to scaled experimentation. Unlike dimensional analysis, the new first-order finite similitude theory can simultaneously target two independent physical properties of common dimension (e.g. initial-yield stress and linear strain hardening). The advantage offered by this feature is demonstrated analytically and numerically in the paper with a focus on axisymmetrical tube buckling and energy absorption. The analytical model serves to expound the theory and the numerical highlights its capabilities and the kinds of accuracy achievable with the new approach.</p

    Equating accelerometer estimates among youth : the Rosetta Stone 2

    Get PDF
    Different accelerometer cutpoints used by different researchers often yields vastly different estimates of moderate-to-vigorous intensity physical activity (MVPA). This is recognized as cutpoint non-equivalence (CNE), which reduces the ability to accurately compare youth MVPA across studies. The objective of this research is to develop a cutpoint conversion system that standardizes minutes of MVPA for six different sets of published cutpoint
    corecore