Wave Propagation Analysis using High-Order Finite Element Methods: Spurious Oscillations excited by Internal Element Eigenfrequencies

From a computational point of view, the numerical analysis of ultrasonic guided waves is still a very demanding task. Because of the high-frequency regime both a fine spatial and temporal discretization is required. To minimize the numerical costs, efficient and robust algorithms ought to be developed. One promising idea is therefore to focus on high-order finite element methods (ho-FEM).The current article investigates the behavior of the p-version of the finite element method (p-FEM) and the spectral element method (SEM) with respect to the existence of spurious oscillations in the solution. Convergence studies have shown that it is possible to observe non-physical oscillations under certain conditions. These parasitic vibrations, however, significantly deteriorate the accuracy of the simulation. For this reason, we analyse this phenomenon in detail and propose solutions to avoid its occurrence.Without loss of generality, we employ a two-dimensional plane strain model to derive a guideline as to how to avoid these spurious oscillations, placing a special emphasis on the relation between the element size, the polynomial degree of the high-order shape functions and the excitation frequency.Our results show that accurate simulations are possible if the model is generated according to the proposed methodology. Moreover, the implementation of the guideline into an existing finite element software is straightforward; these properties turn the method into a useful tool for practical wave propagation analyses

About the Vibration Modes of Square Plate-like Structures

In the experimental vibration analysis of an oil pan, two eigenmodes are observed that did not appear to be those of a standard rectangular plate vibration. As a result, a numerical, analytical and experimental investigation is launched to discover where these modes are originating from. In this paper, the finite element method is applied to determine the vibration behavior numerically, and experimental results are obtained with the help of a laser doppler vibrometer in order to determine the origin of these two eigenmodes

Citizens’ opinions on (non-)essential uses of persistent chemicals: A survey in seven European countries

In accordance with the European Chemicals Strategy for Sustainability towards a Toxic-free Environment, the European Commission plans to phase out persistent chemicals, such as per- and polyfluoroalkyl substances (PFASs), except for uses classified essential for society. Until now, empirical research on what is considered an essential or non-essential chemical use has been lacking. Furthermore, as such criteria are bound to be subjective, different parties can have different views. In this study we explored which uses of persistent chemicals citizens from seven EU countries consider (non-)essential for society. As EU citizens are directly impacted by policy decisions based on (non-)essentiality criteria, we also investigated the influence of emphasis on the consequences of banning vs. allowing persistent chemicals, the association with demographics, and of having heard of persistent chemicals or PFAS prior to the study. We found substantial variation in essentiality ratings within and between use categories and between countries. Uses related to safety were frequently considered essential, whereas uses related to recreation, household, and personal care were frequently considered non-essential. Emphasis on different consequences did not influence essentiality ratings. Gender, age, education, and political orientation were to some extent associated with essentiality ratings. People who had not heard of persistent chemicals or PFAS prior to the study rated uses of persistent chemicals less frequently as non-essential or essential. Our findings offer insight into EU citizens’ opinions on (non-)essential uses of persistent chemicals, and provide empirical input to the scientific and public debate on framing the concept of essential use.</p

Simultaneous real-time measurement of EEG/EMG and L-glutamate in mice: A biosensor study of neuronal activity during sleep

We report on electroencephalograph (EEG) and electromyograph (EMG) measurements concurrently with real-time changes in L-glutamate concentration. These data reveal a link between sleep state and extracellular neurotransmitter changes in a freely-moving (tethered) mouse. This study reveals, for the first time in mice, that the extracellular L-glutamate concentration in the pre-frontal cortex (PFC) increases during periods of extended wakefulness, decreases during extended sleep episodes and spikes during periods of REM sleep. Individual sleep epochs (10 s in duration) were scored as wake, slow-wave (SW) sleep or rapid eye movement (REM) sleep, and then correlated as a function of time with measured changes in L-glutamate concentrations. The observed L-glutamate levels show a statistically significant increase of 0.86 ± 0.26 μM (p < 0.05) over 37 wake episodes recorded from all mice (n = 6). Over the course of 49 measured sleep periods longer than 15 min, L-glutamate concentrations decline by a similar amount (0.88 ± 0.37 μM, p < 0.08). The analysis of 163 individual REM sleep episodes greater than one min in length across all mice (n = 6) demonstrates a significant rise in L-glutamate levels as compared to the 1 min preceding REM sleep onset (RM-ANOVA, DF = 20, F = 6.458, p < 0.001). The observed rapid changes in L-glutamate concentration during REM sleep last only between 1 and 3 min. The approach described can also be extended to other regions of the brain which are hypothesized to play a role in sleep. This study highlights the importance of obtaining simultaneous measurements of neurotransmitter levels in conjunction with sleep markers to help elucidate the underlying physiological and ultimately the genetic components of sleep

Uncoverings: The Research Papers of the American Quilt Study Group, Volume 21 (2000)

Preface by Virginia Gunn Research Papers An Old-Fashioned Quilting in 1910 by Laurel Horton Textiles and Cooperative Commerce in Colonial America: The Example of William McCormick by Xenia E. Cord Creating a New Tradition: Quilting in Tonga by Phyllis S. Herda Better Choose Me : Addictions to Tobacco, Collecting, and Quilting, 1880-1920 by Ethel Ewert Abrahams and Rachel K. Pannabecker Hubert Ver Mehren and Home Art Studios by Susan Price Miller Petting the Fabric : Medium and the Creative Process by Lisa Gabbert Quilts and Their Stories: Revealing a Hidden History by Marsha MacDowell Authors and editor In memoriam: Bill Charles Garoutte (1922-2000), Mill Valley, California In memoriam: Fred Calland (1924-1999) Inde

Protecting eyewitness evidence: Examining the efficacy of a self-administered interview tool

Given the crucial role of eyewitness evidence, statements should be obtained as soon as possible after an incident. This is not always achieved due to demands on police resources. Two studies trace the development of a new tool, the Self-Administered Interview (SAI), designed to elicit a comprehensive initial statement. In Study 1, SAI participants reported more correct details than participants who provided a free recall account, and performed at the same level as participants given a Cognitive Interview. In Study 2, participants viewed a simulated crime and half recorded their statement using the SAI. After a delay of 1 week, all participants completed a free recall test. SAI participants recalled more correct details in the delayed recall task than control participants

Ca2+ imaging of self and other in medial prefrontal cortex during social dominance interactions in a tube test.

The study of social dominance interactions between animals offers a window onto the decision-making involved in establishing dominance hierarchies and an opportunity to examine changes in social behavior observed in certain neurogenetic disorders. Competitive social interactions, such as in the widely used tube test, reflect this decision-making. Previous studies have focused on the different patterns of behavior seen in the dominant and submissive animal, neural correlates of effortful behavior believed to mediate the outcome of such encounters, and interbrain correlations of neural activity. Using a rigorous mutual information criterion, we now report that neural responses recorded with endoscopic calcium imaging in the prelimbic zone of the medial prefrontal cortex show unique correlations to specific dominance-related behaviors. Interanimal analyses revealed cell/behavior correlations that are primarily with an animal's own behavior or with the other animal's behavior, or the coincident behavior of both animals (such as pushing by one and resisting by the other). The comparison of unique and coincident cells helps to disentangle cell firing that reflects an animal's own or the other's specific behavior from situations reflecting conjoint action. These correlates point to a more cognitive rather than a solely behavioral dimension of social interactions that needs to be considered in the design of neurobiological studies of social behavior. These could prove useful in studies of disorders affecting social recognition and social engagement, and the treatment of disorders of social interaction

The ABCD of usability testing

We introduce a methodology for tracking and auditing feedback, errors and suggestions for software packages. This short paper describes how we innovate on the evaluation mechanism, introducing an (Antecedent, Barrier, Consequence and Development) ABCD form, embedded within an eParticipation platform to enable end users to easily report on any usability issues. This methodology will be utilised to improve the STEP cloud eParticipation platform (part of the current STEP Horizon2020 project http://step4youth.eu. The platform is currently being piloted in real life contexts, with the participation of public authorities that are integrating the eParticipation platform into their regular decision-making practices. The project is involving young people, through engagement and motivation strategies and giving them a voice in Environmental decision making at the local level. The pilot evaluation aims to demonstrate how open engagement needs to be embedded within public sector processes and the usability methodology reported here will help to identify the key barriers for wide scale deployment of the platform