Wavenumber sampling strategies for 2.5-D frequency-domain seismic wave modelling in general anisotropic media

The computational efficiency of 2.5-D seismic wave modelling in the frequency domain depends largely on the wavenumber sampling strategy used. This involves determining the wavenumber range and the number of the sampling points, and overcoming the singularities in the wavenumber spectrum when taking the inverse Fourier transform to yield the frequency-domain wave solution. In this paper, we employ our newly developed Gaussian quadrature grid numerical modelling method and extensively investigate the wavenumber sampling strategies for 2.5-D frequency-domain seismic wave modelling in heterogeneous, anisotropic media. We show analytically and numerically that the various components of the Green's function tensor wavenumber-domain solutions have symmetric or antisymmetric properties and other characteristics, all of which can be fully used to construct effective and efficient sampling strategies for the inverse Fourier transform. We demonstrate two sampling schemes-called irregular and regular sampling strategies for the 2.5-D frequency-domain seismic wave modelling technique. The numerical results, which involve calibrations against analytic solutions, comparison of the different wavenumber sampling strategies and validation by means of 3-D numerical solutions, show that the two sampling strategies are both suitable for efficiently computing the 3-D frequency-domain wavefield in 2-D heterogeneous, anisotropic media. These strategies depend on the given frequency, elastic model parameters and maximum wavelength and the offset distance from the sourc

2.5-D/3-D resistivity modelling in anisotropic media using Gaussian quadrature grids

We present a new numerical scheme for 2.5-D/3-D direct current resistivity modelling in heterogeneous, anisotropic media. This method, named the ‘Gaussian quadrature grid' (GQG) method, cooperatively combines the solution of the Variational Principle of the partial differential equation, Gaussian quadrature abscissae and local cardinal functions so that it has the main advantages of the spectral element method. The formulation shows that the GQG method is a modification of the spectral element method but does not employ the constant elements or require the mesh generator to match the Earth's surface. This makes it much easier to deal with geological models having a 2-D/3-D complex topography than using traditional numerical methods. The GQG technique can achieve a similar convergence rate to the spectral element method. We show it transforms the 2.5-D/3-D resistivity modelling problem into a sparse and symmetric linear equation system that can be solved by an iterative or matrix inversion method. Comparison with analytic solutions for homogeneous isotropic and anisotropic models shows that the error depends on the Gaussian quadrature order (abscissa number) and the subdomain size. The higher the order or the smaller the subdomain size that is employed, the more accurate are the results obtained. Several other synthetic examples, both homogeneous and inhomogeneous, incorporating sloping, undulating and severe topography, are presented and found to yield results comparable to finite element solutions involving a dense mes

ATHENE : Assistive technologies for healthy living in elders : needs assessment by ethnography

Numerous assistive technologies to support independent living –including personal alarms, mobile phones, self-monitoring devices, mobility aids, software apps and home adaptations –have been developed over the years, but their uptake by older people, especially those from minority ethnic groups, is poor. This paper outlines the ways in which the ATHENE project seeks to redress this situation by producing a richer understanding of the complex and diverse living experiences and care needs of older people and exploring how industry, the NHS, social services and third sector can work with the older people themselves to ‘co-produce’ useful and useable ALT designs to meet their needs. In this paper, we provide an overview of the project methodology and discuss some of the issues it raises for the design and development process

Resistivity inversion in 2-D anisotropic media: numerical experiments

Many rocks and layered/fractured sequences have a clearly expressed electrical anisotropy although it is rare in practice to incorporate anisotropy into resistivity inversion. In this contribution, we present a series of 2.5-D synthetic inversion experiments for various electrode configurations and 2-D anisotropic models. We examine and compare the image reconstructions obtained using the correct anisotropic inversion code with those obtained using the false but widely used isotropic assumption. Superior reconstruction in terms of reduced data misfit, true anomaly shape and position, and anisotropic background parameters were obtained when the correct anisotropic assumption was employed for medium to high coefficients of anisotropy. However, for low coefficient values the isotropic assumption produced better-quality results. When an erroneous isotropic inversion is performed on medium to high level anisotropic data, the images are dominated by patterns of banded artefacts and high data misfits. Various pole-pole, pole-dipole and dipole-dipole data sets were investigated and evaluated for the accuracy of the inversion result. The eigenvalue spectra of the pseudo-Hessian matrix and the formal resolution matrix were also computed to determine the information content and goodness of the results. We also present a data selection strategy based on high sensitivity measurements which drastically reduces the number of data to be inverted but still produces comparable results to that of the comprehensive data set. Inversion was carried out using transversely isotropic model parameters described in two different co-ordinate frames for the conductivity tensor, namely Cartesian versus natural or eigenframe. The Cartesian frame provided a more stable inversion product. This can be simply explained from inspection of the eigenspectra of the pseudo-Hessian matrix for the two model description

Ergonomic Assessment of a Robotic Assisted Transfer Device for Conducting Caregiver Assisted Wheelchair Transfers

Depending on the nature of an injury or illness, a care recipient benefits from caregiver assistance when moving to and from a target surface, a maneuver known as an assisted transfer. When performed manually, that is physically with no assistance, a transfer exposes the caregiver to muscle fatigue in the back, shoulders, and upper extremities, endangering themselves as well as their care recipient. Because of the relief they provide caregivers, transfer lift systems are becoming a common clinical standard to counter exposure to such risk factors. Use of such devices improves the safety of performing transfers as well as their efficiency. As the population continues to age and society becomes more inclusive of disability, it is imperative to advance such technologies as to improve their usability in and out of a clinical workspace. Robotics present a unique opportunity for caregivers to perform a safe and effective transfer while reducing the risk for musculoskeletal injury and progressing independent living for a mobility device user. The purpose of this project was to assess caregivers performing transfers using a portable, ambidextrous robotic assisted transfer device (RATD). This was performed over the course of two studies: (1) a “proof of concept” assessment in which the trunk kinematics and usability feedback from caregivers (N=21) were compared between a prototype of the novel RATD and a Mechanical Floor Lift (the clinical standard of care), and (2) an ergonomic assessment in which caregivers (N=28) conducted transfers on their paired care recipient (N=28) using a second generation RATD, from which trunk kinematics, usability feedback, cognitive load, and muscle activation was compared to the Mechanical Floor Lift. The outcomes of both studies provided insight and promise into the application of a novel engineering concept to advance performance of a critical activity of daily living (ADL) for people living with a mobility impairment as well as to improve quality of care delivery provided by their caregivers

Using Creativity from Art and Engineering to Engage Students in Science

STEAM education, referring to integrated Science, Technology, Engineering, Art, and Mathematics, is a contemporary buzzword that is popular in many schools. In particular, many elementary school teachers who have been tasked to incorporate STEM teaching, because of the requirements of the Next Generation Science Standards, attempt to apply the arts in their science curriculum because they feel more comfortable using instructional approaches that incorporate creative activities such as crafts, drawing, and model construction than the core practices of STEM disciplines. Teachers can use the creative arts activities in two ways to enhance the STEM learning environment: 1) Using creative processes as a way to gain access to students’ ideas before science content is taught, to help guide further instruction; and 2) Using creativity as a means for students to express their understanding of science content. In this editorial, we explore how the arts can help students generate “Big Ideas” about science, construct questions, and share their understanding of the topic with authentic audiences. We will also discuss the scope and nature of discipline of specific STEM fields and how the arts could be incorporated into these practices

You Can Lead a Horse to Water: Mapping Seasonal Water Resources to Predict Wild Horse Movements on Utah Rangelands

All wild horse herd management areas in Utah overlap BLM grazing allotments. Although horses and cattle have similar dietary habits, both species rely heavily on predictable water sources during dry periods. The concentration of wildlife and livestock in mesic areas during droughts can become problems for farmers and livestock producers. We aimed to map the annual distribution of temporary surface water across Utah that cattle, horses, and wildlife could use. Herein we analyzed an 18-year record of satellite imagery to create a statewide map of seasonal surface-water availability for agricultural and wildlife management purposes