An Arc-Consistent Viscous-Spring Artificial Boundary for Numerical Analysis of Seismic Response of Underground Structures

A new arc-consistent viscous-spring artificial boundary (ACVAB) was proposed by changing a traditional flat artificial boundary based on the theory of viscous-spring artificial boundaries. Through examples, the concept underpinning the establishment and specific setting of the boundary in the finite element software were described. Through comparison with other commonly used artificial boundaries in an example for near-field wave analysis using the two-dimensional (2D) half-space model, the reliability of the ACVAB was verified. Furthermore, the ACVAB was used in the numerical analysis of the effects of an earthquake on underground structures. The results were compared with the shaking table test results on underground structures. On this basis, the applicability of the ACVAB to a numerical model of seismic response of underground structures was evaluated. The results show that the boundary is superior to common viscous-spring boundaries in terms of accuracy and stability, and therefore, it can be used to evaluate radiation damping effects of seismic response of underground structures and is easier to use.

An Arc-consistent Viscous-spring Artificial Boundary for Numerical Analysis of the Seismic Response of Underground Structures

A new arc consistent viscous-spring artificial boundary (ACVAB) was proposed by changing a traditional flat artificial boundary based on the theory of viscous-spring artificial boundaries. Through examples, the concept underpinning the establishment, and specific setting of, the boundary in the finite element software were described. Through comparison with other commonly used artificial boundaries in an example for near-field wave analysis using the two-dimensional (2-d) half-space model, the reliability of the ACVAB was verified. Furthermore, the ACVAB was used in the numerical analysis of the effects of an earthquake of underground structures. The results were compared with shaking-table test results on underground structures. On this basis, the applicability of the ACVAB to a numerical model of the seismic response of underground structures was evaluated. The results show that the boundary is superior to common viscous-spring boundaries in terms of accuracy and stability, and therefore it can be used to evaluate radiation damping effects of seismic response of underground structures and is easier to use.

Electromagnetic Devices with Moving Parts—Simulation with FEM/BEM Coupling

The numerical analysis of electromagnetic devices by means of finite element methods (FEM) is often hindered by the need to incorporate the surrounding domain. The discretisation of the air may become complex and has to be truncated by artificial boundaries incurring a modelling error. Even more problematic are moving parts that require tedious re-meshing and mapping techniques. In this work, we tackle these problems by using the boundary element method (BEM) in conjunction with FEM. Whereas the solid parts of the electrical device are discretised by FEM, which can easily account for material non-linearities, the surrounding domain is represented by BEM, which requires only a surface discretisation. This approach completely avoids an air mesh and its re-meshing during the simulation with moving or deforming parts. Our approach is robust, shows optimal complexity, and provides an accurate calculation of electromagnetic forces that are required to study the mechanical behaviour of the device.

Ecological Interface Design and Head-Up Displays: The Contact-Analog Visualization Tradeoff

Objective This study investigated how the visualization of an ecological interface affects its subjective and objective usefulness. Therefore, we compared a simple 2D visualization against a contact-analog 3D visualization. Background Recently, head-up displays (HUDs) have become contact-analog and visualizations have been enabled to be merged with the real environment. In this regard, ecological interface design visualizing boundaries of acceptable performance might be a perfect match. Because the real-world environment already provides such boundaries (e.g., lane markings), the interface might directly use them. However, visual illusions and undesired interference with the environment might influence the overall usability. Method To allow for a comparison, 49 participants tested the same ecological interface in two configurations, contact-analog (3D) and two dimensional (2D). Both visualizations were shown in the car’s head-up display (HUD). Results The driving simulator experiment reveals that 3D was rated as more demanding and more disturbing, but also more innovative and appealing. However, regarding driving performance, the 3D representation decreased the accuracy of speed control by 6% while significantly increasing lane stability by 20%. Conclusion We conclude that, if we want environmental boundaries guiding our behavior, the indicator for the behavior should be visualized contact-analog. If we desire artificial boundaries (e.g., speed limits) to guide behavior, the behavioral indicator should be visualized in 2D. This is less prone to optical illusions and allows for a more precise control of behavior. Application These findings provide guidance to human factors engineers, how contact-analog visualizations might be used optimally.

Discriminating arboviral species

Mosquito-borne arboviruses, including a diverse array of alphaviruses and flaviviruses, lead to hundreds of millions of human infections each year. Current methods for species-level classification of arboviruses adhere to guidelines prescribed by the International Committee on Taxonomy of Viruses (ICTV), and generally apply a polyphasic approach that might include information about viral vectors, hosts, geographical distribution, antigenicity, levels of DNA similarity, disease association and/or ecological characteristics. However, there is substantial variation in the criteria used to define viral species, which can lead to the establishment of artificial boundaries between species and inconsistencies when inferring their relatedness, variation and evolutionary history. In this study, we apply a single, uniform principle – that underlying the Biological Species Concept (BSC) – to define biological species of arboviruses based on recombination between genomes. Given that few recombination events have been documented in arboviruses, we investigate the incidence of recombination within and among major arboviral groups using an approach based on the ratio of homoplastic sites (recombinant alleles) to non-homoplastic sites (vertically transmitted alleles). This approach supports many ICTV-designations but also recognizes several cases in which a named species comprises multiple biological species. These findings demonstrate that this metric may be applied to all lifeforms, including viruses, and lead to more consistent and accurate delineation of viral species.

The “Scientific colour map” Initiative: Version 7 and its new additions

<ul><li><em>Does visualisation hinder scientific progress?</em></li> <li><em>Is visualisation widely misused to tweak data?</em></li> <li><em>Is visualisation intentionally used for social exclusion?</em></li> <li><em>Is visualisation taken seriously by academic leaders?</em></li> </ul><p>Using scientifically-derived colour palettes is a big step towards making it obsolete to even ask such brutal questions. Their perceptual uniformity leaves no room to highlight artificial boundaries, or hide real ones. Their perceptual order visually transfers data effortlessly and without delay. Their colour-vision deficient friendly nature leaves no reader left wondering. Their black-and-white readability leaves no printer accused of being not good enough. It is, indeed, the true nature of the data that is displayed to all viewers, in every way.</p><p>The “Scientific colour map” initiative (<em>Crameri et al., 2020</em>) provides free, citable colour palettes of all kinds for download for an extensive suite of software programs, a discussion around data types and colouring options, and a handy how-to guide for a professional use of colour combinations. Version 7 of the Scientific colour maps (<em>Crameri, 2020</em>) makes crucial new additions towards fairer and more effective science communication available to the science community.</p><p>Crameri, F., G.E. Shephard, and P.J. Heron (2020), The misuse of colour in science communication, Nature Communications, 11, 5444. </p><p>Crameri, F. (2020). Scientific colour maps. Zenodo. http://doi.org/10.5281/zenodo.1243862</p>

Implementing a Parallel Version of a Variational Scheme in a Global Assimilation System at Eddy-Resolving Resolution

Recent advances in global ocean prediction systems are fostered by the needs of accurate representation of mesoscale processes. The day-by-day realistic representation of its variability is hampered by the scarcity of observations as well as the capability of assimilation systems to correct the ocean states at the same scale. This work extends a 3DVAR system designed for oceanic applications to cope with global eddy-resolving grid and dense observational datasets in a hybridly parallelized environment. The efficiency of the parallelization is assessed in terms of both scalability and accuracy. The scalability is favored by a weak-constrained formulation of the continuity requirement among the artificial boundaries implied by the domain decomposition. The formulation forces possible boundary discontinuities to be less than a prescribed error and minimizes the parallel communication relative to standard methods. In theory, the exact solution is recovered by decreasing the boundary error toward zero. In practice, it is shown that the accuracy increases until a lower bound arises, because of the presence of the mesh and the finite accuracy of the minimizer. A twin experiment has been set up to estimate the benefit of employing an eddy-resolving grid within the assimilation step, as compared with an eddy-permitting one, while keeping the eddy-resolving grid within the forecast step. It is shown that the use of a coarser grid for data assimilation does not allow an optimal exploitation of the present remote sensing observation network. A global decrease of about 15% in the error statistics is found when assimilating dense surface observations, and no significant improvement is seen for sparser observations (in situ profilers).

The Double Absorbing Boundary Method Incorporated in a High-Order Spectral Element Formulation

In this paper, we consider the numerical solution of the time-dependent wave equation in a semi-infinite waveguide. We employ the Double Absorbing Boundary (DAB) method, by introducing two parallel artificial boundaries on the side where waves are outgoing. In contrast to the original implementation of the DAB, where the numerical solution involved either a low-order finite difference scheme or a low-order finite element scheme, here we incorporate the DAB into a high-order spectral element formulation, which provides us with very accurate solutions of wave problems in unbounded domains. This is demonstrated by numerical experiments. While the method is highly accurate, it suffers from long-time instability. We show how to postpone the onset of the instability by a prudent choice of the computational parameters.