Nonlinear Modeling and Verification of a Heaving Point Absorber for Wave Energy Conversion

Although the heaving Point Absorber (PA) concept is well known in wave energy conversion research, few studies focus on appropriate modelling of non-linear fluid viscous and mechanical friction dynamics. Even though these concepts are known to have non-linear effects on the hydrodynamic system, most research studies consider linearity as a starting point and in so doing have a weak approach to modelling the true dynamic behaviour, particularly close to resonance. The sole use of linear modelling leads to limited ability to develop control strategies capable of true power capture optimisation and suitable device operation. Based on a 1/50 scale cylindrical heaving PA, this research focuses on a strategy for hydrodynamic model development and experimental verification. In this study, nonlinear dynamics are considered, including the lumped effect of the fluid viscous and mechanical friction forces. The excellent correspondence between the derived non-linear model and wave tank tested PA behaviours provides a strong background for wave energy tuning and control system design

The Impact of COVID-19 on Wildlife Strike Rates in the United States

Shortly after the COVID-19 pandemic impacted air traffic, industry bodies warned of the potential increase in wildlife strike risk. Prior to the pandemic, wildlife strikes were already a concern to the industry. We sought to evaluate industry warnings using interrupted time series analysis of wildlife strike trends in the United States. Using pre-pandemic wildlife strike trends, we compared a forecast of the expected monthly strike rates through the COVID-19 impact period (March 2020 to December 2020) to the actual wildlife strike rates for the same period. Our results showed an increase in wildlife strike rates in 5 out of the 10 months analyzed, supporting the need for careful consideration of wildlife strike risk through the industry’s recovery

Tools and Procedures for the CTA Array Calibration

The Cherenkov Telescope Array (CTA) is an international initiative to build the next generation ground-based very-high-energy gamma-ray observatory. Full sky coverage will be assured by two arrays, one located on each of the northern and southern hemispheres. Three different sizes of telescopes will cover a wide energy range from tens of GeV up to hundreds of TeV. These telescopes, of which prototypes are currently under construction or completion, will have different mirror sizes and fields-of-view designed to access different energy regimes. Additionally, there will be groups of telescopes with different optics system, camera and electronics design. Given this diversity of instruments, an overall coherent calibration of the full array is a challenging task. Moreover, the CTA requirements on calibration accuracy are much more stringent than those achieved with current Imaging Atmospheric Cherenkov Telescopes, like for instance: the systematic errors in the energy scale must not exceed 10%.In this contribution we present both the methods that, applied directly to the acquired observational CTA data, will ensure that the calibration is correctly performed to the stringent required precision, and the calibration equipment that, external to the telescopes, is currently under development and testing. Moreover, some notes about the operative procedure to be followed with both methods and instruments, will be described. The methods applied to the observational CTA data include the analysis of muon ring images, of carefully selected cosmic-ray air shower images, of the reconstructed electron spectrum and that of known gamma-ray sources and the possible use of stereo techniques hardware-independent. These methods will be complemented with the use of calibrated light sources located on ground or on board unmanned aerial vehicles.Comment: All CTA contributions at arXiv:1709.0348

Response of river-dominated delta channel networks to permanent changes in river discharge

Using numerical experiments, we investigate how river-dominated delta channel networks are likely to respond to changes in river discharge predicted to occur over the next century as a result of environmental change. Our results show for a change in discharge up to 60% of the initial value, a decrease results in distributary abandonment in the delta, whereas an increase does not significantly affect the network. However, an increase in discharge beyond a threshold of 60% results in channel creation and an increase in the density of the distributary network. This behavior is predicted by an analysis of an individual bifurcation subject to asymmetric water surface slopes in the bifurcate arms. Given that discharge in most river basins will change by less than 50% in the next century, our results suggest that deltas in areas of increased drought will be more likely to experience significant rearrangement of the delta channel network. Copyright 2010 by the American Geophysical Union

I'll be dead by the time it happens: Children's Perceptions of Climate Change in the Mekong Delta, Vietnam

The Mekong Delta in Southern Vietnam is one of the most at risk places globally to the effects of climate change and sea level rise, specifically in terms of flooding. It is predicted to change drastically over the next 100 years, with additional human-driven actions (such as sand mining and groundwater extraction) expected to exasperate the speed and severity of said change. Understanding the existing perceptions of those that will face these future challenges, and what contributes to forming those perceptions, is a critical underpinning required for the success of any future resilience and mitigation initiatives. A holistic view that takes account of these varying influences on societal perceptions, resilience and education needs to be taken. One of the most vulnerable groups to the consequences of climate change, and indeed the citizens that will go on to tackle the majority of challenges we are predicted to face in the future, is children. For this reason alone, ascertaining their perceptions and understandings, along with the influences and sources that shape their views, is paramount.This paper will present the findings from a project that explored local children’s perceptions of climate change in the heart of the Mekong Delta. Creative and arts-based methods enabled children’s voices to be heard. Combined with further policy analysis and interviews with parents, teachers and government officials, these voices have been further contextualised within their socio-cultural context and environment. Through developing an understanding of these perceptions and the influencing factors, a more effective and holistic approach to shaping children’s climate change resilience can be executed, which will ultimately enhance a society’s ability to adapt to and mitigate the impacts of climate change into the future

Calibration of the Cherenkov Telescope Array

The construction of the Cherenkov Telescope Array is expected to start soon. We will present the baseline methods and their extensions currently foreseen to calibrate the observatory. These are bound to achieve the strong requirements on allowed systematic uncertainties for the reconstructed gamma-ray energy and flux scales, as well as on the pointing resolution, and on the overall duty cycle of the observatory. Onsite calibration activities are designed to include a robust and efficient calibration of the telescope cameras, and various methods and instruments to achieve calibration of the overall optical throughput of each telescope, leading to both inter-telescope calibration and an absolute calibration of the entire observatory. One important aspect of the onsite calibration is a correct understanding of the atmosphere above the telescopes, which constitutes the calorimeter of this detection technique. It is planned to be constantly monitored with state-of-the-art instruments to obtain a full molecular and aerosol profile up to the stratosphere. In order to guarantee the best use of the observation time, in terms of usable data, an intelligent scheduling system is required, which gives preference to those sources and observation programs that can cope with the given atmospheric conditions, especially if the sky is partially covered by clouds, or slightly contaminated by dust. Ceilometers in combination with all-sky-cameras are plannned to provide the observatory with a fast, online and full-sky knowledge of the expected conditions for each pointing direction. For a precise characterization of the adopted observing direction, wide-field optical telescopes and Raman Lidars are planned to provide information about the height-resolved and wavelength-dependent atmospheric extinction, throughout the field-of-view of the cameras

Real-time social media sentiment analysis for rapid impact assessment of floods

Traditional approaches to flood modelling mostly rely on hydrodynamic physical simulations. While these simulations can be accurate, they are computationally expensive and prohibitively so when thinking about real-time prediction based on dynamic environmental conditions.Alternatively, social media platforms such as Twitter are often used by people to communicate during a flooding event, but discovering which tweets hold useful information is the key challenge in extracting information from posts in real time.In this article, we present a novel model for flood forecasting and monitoring that makes use of a transformer network that assesses the severity of a flooding situation based on sentiment analysis of the multimodal inputs (text and images). We also present an experimental comparison of a range of state-of-the-art deep learning methods for image processing and natural language processing. Finally, we demonstrate that information induced from tweets can be used effectively to visualise fine-grained geographical flood-related information dynamically and in real-time

The First 10 Years of NeuroIS: A Systematic Literature Review of NeuroIS Publications (2007 - 2017)

NeuroIS is an emerging and promising academic field that has attracted increasing attention. The year 2017 signifies the 10th year of existence of NeuroIS as a research field in information systems area. In this study, we conduct a systematic literature review of the NeuroIS academic research publications of last 10 years (2007-2017). As a result, we categorize the existent NeuroIS literature into 8 groups, explore the correlations among various NeuroIS concepts/ constructs, and demonstrate how the study enhances our understanding of the granulated inter-relationships between pairs of NeuroIS elements. The implications of the result to the NeuroIS research community are discussed

Three-dimensional flow structure and bed morphology in large elongate meander loops with different outer bank roughness characteristics

© 2016. American Geophysical Union. All Rights Reserved. Few studies have examined the three-dimensional flow structure and bed morphology within elongate loops of large meandering channels. The present study focuses on the spatial patterns of three-dimensional flow structure and bed morphology within two elongate meander loops and examines how differences in outer bank roughness influence near-bank flow characteristics. Three-dimensional velocities were measured during two different events—a near-bankfull flow and an overbank event. Detailed data on channel bathymetry and bed form geometry were obtained during a near-bankfull event. Flow structure within the loops is characterized by strong topographic steering by the point bar, by the development of helical motion associated with flow curvature, and by acceleration of flow where bedrock is exposed along the outer bank. Near-bank velocities during the overbank event are less than those for the near-bankfull flow, highlighting the strong influence of the point bar on redistribution of mass and momentum of the flow at subbankfull stages. Multiple outer bank pools are evident within the elongate meander loop with low outer bank roughness, but are not present in the loop with high outer bank roughness, which may reflect the influence of abundant large woody debris on near-bank velocity characteristics. The positions of pools within both loops can be linked to spatial variations in planform curvature. The findings indicate that flow structure and bed morphology in these large elongate loops is similar to that in small elongate loops, but differs somewhat from flow structure and bed morphology reported for experimental elongate loops