Showing papers by "Dublin City University published in 2021"

The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1. I. Direction-dependent calibration and imaging

Abstract: The Low Frequency Array (LOFAR) is an ideal instrument to conduct deep extragalactic surveys. It has a large field of view and is sensitive to large-scale and compact emission. It is, however, very challenging to synthesize thermal noise limited maps at full resolution, mainly because of the complexity of the low-frequency sky and the direction dependent effects (phased array beams and ionosphere). In this first paper of a series, we present a new calibration and imaging pipeline that aims at producing high fidelity, high dynamic range images with LOFAR High Band Antenna data, while being computationally efficient and robust against the absorption of unmodeled radio emission. We apply this calibration and imaging strategy to synthesize deep images of the Bootes and Lockman Hole fields at ~150 MHz, totaling ~80 and ~100 h of integration, respectively, and reaching unprecedented noise levels at these low frequencies of ≲30 and ≲23 μ Jy beam−1 in the inner ~3 deg2 . This approach is also being used to reduce the LOTSS-wide data for the second data release.

Mental Health Among Medical Professionals During the COVID-19 Pandemic in Eight European Countries: Cross-sectional Survey Study.

Abstract: Background: The death toll of COVID-19 topped 170,000 in Europe by the end of May 2020. COVID-19 has caused an immense psychological burden on the population, especially among doctors and nurses who are faced with high infection risks and increased workload. Objective: The aim of this study was to compare the mental health of medical professionals with nonmedical professionals in different European countries during the COVID-19 pandemic. We hypothesized that medical professionals, particularly those exposed to COVID-19 at work, would have higher levels of depression, anxiety, and stress. We also aimed to determine their main stressors and most frequently used coping strategies during the crisis. Methods: A cross-sectional online survey was conducted during peak COVID-19 months in 8 European countries. The questionnaire included demographic data and inquired whether the participants were exposed to COVID-19 at work or not. Mental health was assessed via the Depression Anxiety Stress Scales32 (23.53)–21 (DASS-21). A 12-item checklist on preferred coping strategies and another 23-item questionnaire on major stressors were completed by medical professionals. Results: The sample (N=609) consisted of 189 doctors, 165 nurses, and 255 nonmedical professionals. Participants from France and the United Kingdom reported experiencing severe/extremely severe depression, anxiety, and stress more often compared to those from the other countries. Nonmedical professionals had significantly higher scores for depression and anxiety. Among medical professionals, no significant link was reported between direct contact with patients with COVID-19 at work and anxiety, depression, or stress. “Uncertainty about when the epidemic will be under control” caused the most amount of stress for health care professionals while “taking protective measures” was the most frequently used coping strategy among all participants. Conclusions: COVID-19 poses a major challenge to the mental health of working professionals as a considerable proportion of our participants showed high values for depression, anxiety, and stress. Even though medical professionals exhibited less mental stress than nonmedical professionals, sufficient help should be offered to all occupational groups with an emphasis on effective coping strategies.

In-situ sensing, process monitoring and machine control in Laser Powder Bed Fusion: A review

Abstract: Process monitoring and sensing is widely used across many industries for quality assurance, and for increasing machine uptime and reliability. Though still in the emergent stages, process monitoring is beginning to see strong adoption in the additive manufacturing community through the use of process sensors recording a wide range of optical, acoustic and thermal signals. The ability to acquire these signals in a holistic manner, coupled with intelligence-based machine control has the potential to make additive manufacturing a robust and competitive alternative to conventional fabrication techniques. This paper presents an overview of the state-of the art of in-situ process monitoring in laser powder bed fusion processes and highlights some current limitations and areas for advancement. Also presented is an overview of real-time process control requirements, which when combined with the emergent process monitoring tools, will eventually allow for in-depth process control of the powder bed fusion process, which is essential for wide-scale industrial credibility and adoption of this technology.

Mixed-Methods Research: A Discussion on its Types, Challenges, and Criticisms

Abstract: The article positions mixed-method research (MMR) as a principled complementary research method to the traditional quantitative and qualitative research approaches. By situating MMR in an analysis of some of the common research paradigms, the article presents it as a natural choice in order to complement and cater to the increasingly complex needs of contemporary researchers. It proffers MMR as a flexible and adaptive conceptual framework for designing and conducting mixed methods research in a simplified manner. By explaining fundamental principles and major theoretical tenets of a mixed-methods approach, which involves both quantitative and qualitative data collection in response to research questions, it elucidates several benefits of adopting MMR since it integrates post-positivism as well as interpretivism frameworks. There is abundant literature around this research design aiming to provide researchers an understanding of the approach. Yet there is limited literature that provides illustrative guidance to research novices in comprehending mixed methods, understanding reasons for choosing it, and selecting an appropriate mixed methods design. Based on an analysis of some notable works in the field, this article provides an overview of mixed methods designs, discusses its main types, and explains challenges one can potentially encounter when in using them with a view to assisting early career researchers in particular and other researchers in general.

Leading through paradox in a COVID-19 world: Human resources comes of age

Abstract: The impact of the coronavirus disease (COVID‐19) pandemic is unprecedented. At an organisational level, the crisis has been hugely disruptive, complex and fraught with ambiguity for leaders. The crisis is fundamentally a human one, making human resource (HR) leaders central in enabling organisations to manage through and ultimately exit the crisis successfully. We apply a paradox lens to understand the HR leadership challenges posed by the COVID‐19 crisis. We argue that how the HR function responds to the challenges ofthe crisis and its role in mapping the exit route from the crisis are likely to shape the trajectory of the function for decades to come. The pandemic creates an unprecedented opportunity to elevate the status of the HR function in organisations where it has struggled to gain status and to reinforce the influence of the function in those where it already enjoys legitimacy. The value of this is likely to be reflected in more sustainable performance through the alignment of people and purpose and balancing the short and long term objectives of the organisation

Community Translation: Translation as a social activity and its possible consequences in the advent of Web 2.0 and beyond

Abstract: This introduction to the 10th issue of Linguistica Antverpiensia New Series – Themes in translation Studies (LANS-TTS) begins by discussing the central concept of community translation, highlighting its terminological ambiguity. This is in part due to the already well-established field of community interpreting where the term is often used to mean the written translation of public information for immigrants. It is also an indication of the terminological instability typical of an emerging paradigm. For example, community translation is used more or less synonymously with such terms as translation crowdsourcing, user-generated translation and collaborative translation. The meaning of the term as we discuss in this issue can be best specified when the concept is anchored in the context of Web 2.0 (second generation web-technologies). This in turn acknowledges its intrinsic tie to online communities and directs us to new dynamics resulting from general Internet users acting as translators. While participants in community translation are not necessarily all unpaid, untrained volunteers community translation is used by some organisations as a mechanism to obtain free translations by going outside the professional translation sphere. To this end the ethical question of profit-making enterprises accessing free labour on the pretext of openness and sharing remains. That said, the author believes community translation is far more than a dilettante, anti-professional movement. Building on the emerging picture from the contributions in this volume, the author suggests some of the future directions that research on community translation might take, emphasising the need to reflect on the current translation practices and be open to the new developments and opportunities arising from the free and social Internet.

Generative Adversarial Networks in Computer Vision: A Survey and Taxonomy

Abstract: Generative adversarial networks (GANs) have been extensively studied in the past few years Arguably their most significant impact has been in the area of computer vision where great advances have been made in challenges such as plausible image generation, image-to-image translation, facial attribute manipulation, and similar domains Despite the significant successes achieved to date, applying GANs to real-world problems still poses significant challenges, three of which we focus on here These are as follows: (1) the generation of high quality images, (2) diversity of image generation, and (3) stabilizing training Focusing on the degree to which popular GAN technologies have made progress against these challenges, we provide a detailed review of the state-of-the-art in GAN-related research in the published scientific literature We further structure this review through a convenient taxonomy we have adopted based on variations in GAN architectures and loss functions While several reviews for GANs have been presented to date, none have considered the status of this field based on their progress toward addressing practical challenges relevant to computer vision Accordingly, we review and critically discuss the most popular architecture-variant, and loss-variant GANs, for tackling these challenges Our objective is to provide an overview as well as a critical analysis of the status of GAN research in terms of relevant progress toward critical computer vision application requirements As we do this we also discuss the most compelling applications in computer vision in which GANs have demonstrated considerable success along with some suggestions for future research directions Codes related to the GAN-variants studied in this work is summarized on https://githubcom/sheqi/GAN_Review

Influences of powder morphology and spreading parameters on the powder bed topography uniformity in powder bed fusion metal additive manufacturing

Abstract: Powder spreading is a crucial step in the powder bed fusion process, which controls the quality of powder bed and consequently affects the quality of printed parts. To date, however, powder spreadability has received very little attention and substantial fundamental work is still needed, largely because of the lack of experimental studies. Therefore, the focus of the present study addresses the influences of powder morphology, spreading velocity and layer thickness on the powder bed topography uniformity. The experiments were conducted with a laser powder bed fusion printer and the powder layers were spread systematically and comprehensively assessed. In summary, it was found that particle sphericity and surface texture dictates the degree of impact that the spreader velocity and the layer thickness exert on the quality of powder bed topography in spread layers. The spreader velocity has substantial influence on powder bed uniformity, such that better uniformity is achieved with low spreading velocities, ≤ 80 mm/s. Powders with a wide particle distribution and containing large number of fine particles (

Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

Abstract: We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies.

Melting performance enhancement of PCM based thermal energy storage system using multiple tubes and modified shell designs

Abstract: In this paper, experimental and numerical investigations are performed for heat transfer enhancement in a horizontal Latent Thermal Energy Storage System using multiple heat transfer tubes and modified shell designs. Stearic acid is used as phase change material and it is placed in the annulus of steel shell and copper tubes carrying water as the heat transfer fluid (HTF). A single Y-fin HTF tube, used as Base Case, is split up into 2 – 5 tubes with different arrangements while ensuring constant mass of the PCM. The vertical double tube and triple tube V-configuration improve the average heat transfer rates by 33.6% and 23.7%, respectively, as compared to the Base Case. The corresponding complete melting times is also reduced by 27.7% and 21.7%. Additionally, elliptic and triangular shell design modifications are proposed for double and triple tube arrangements, respectively. Both configurations increase the average heat transfer rate by 85% which results in reduction of the complete PCM melting time by 50% with respect to Base Case of Y-fins single tube arrangement. In comparison to the Base Case, an increase in HTF temperature of 5.6% improves the average Nusselt number by more than 37% for both the cases. Additionally, the correlations for melting Fourier number and average Nusselt number are also developed.

The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1 - II. The ELAIS-N1 LOFAR deep field

Abstract: The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ~10 microJy/bm over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 hours, it reaches a root mean square (RMS) noise level below 20 microJy/bm in the central region (and below 30 microJy/bm over 10 square degrees). The resolution is 6 arcsecs and 84862 radio sources were detected in the full area (68 sq. deg.) with 74127 sources in the highest quality area at less than 3 degrees from the pointing centre. The observation reaches a sky density of more than 5000 sources per sq. deg. in the central ~5 sq. deg. region. We present the calibration procedure, which addresses the special configuration of some observations and the extended bandwidth covered (115 to 177 MHz; central frequency 146.2 MHz) compared to standard LoTSS. We also describe the methods used to calibrate the flux density scale using cross-matching with sources detected by other radio surveys in the literature. We find the flux density uncertainty related to the flux density scale to be ~6.5%. By studying the variations of the flux density measurements between different epochs, we show that relative flux density calibration is reliable out to about a 3 degree radius, but that additional flux density uncertainty is present for all sources at about the 3 per cent level; this is likely to be associated with residual calibration errors, and is shown to be more significant in datasets with poorer ionosphere conditions. We also provide intra-band spectral indices, which can be useful to detect sources with unusual spectral properties. The final uncertainty in the flux densities is estimated to be ~10% for ELAIS-N1.

A look into the future of the COVID-19 pandemic in Europe: an expert consultation.

Abstract: How will the coronavirus disease 2019 (COVID-19) pandemic develop in the coming months and years? Based on an expert survey, we examine key aspects that are likely to influence the COVID-19 pandemic in Europe. The challenges and developments will strongly depend on the progress of national and global vaccination programs, the emergence and spread of variants of concern (VOCs), and public responses to non-pharmaceutical interventions (NPIs). In the short term, many people remain unvaccinated, VOCs continue to emerge and spread, and mobility and population mixing are expected to increase. Therefore, lifting restrictions too much and too early risk another damaging wave. This challenge remains despite the reduced opportunities for transmission given vaccination progress and reduced indoor mixing in summer 2021. In autumn 2021, increased indoor activity might accelerate the spread again, whilst a necessary reintroduction of NPIs might be too slow. The incidence may strongly rise again, possibly filling intensive care units, if vaccination levels are not high enough. A moderate, adaptive level of NPIs will thus remain necessary. These epidemiological aspects combined with economic, social, and health-related consequences provide a more holistic perspective on the future of the COVID-19 pandemic.

Melting performance enhancement of a phase change material using branched fins and nanoparticles for energy storage applications

Abstract: This study presents the application of branched fins and nanoparticles to enhance the melting of phase change material (PCM) placed in a horizontally configured latent heat thermal energy storage (LHTES) unit. The mathematical model governing the transient melting of PCM is numerically solved for 2D planar geometries. The numerical solution procedure is validated against literature as well as our experimental results. First, the effects of different fin designs on melting performance are analyzed using pure PCM. All-straight, single-branched and double-branched fin designs are seen to enhance melting through efficient heat transfer resulting in time savings of 22.9%, 35.4% and 45.9%, respectively, as compared to a Y-oriented triple-fin Base Case. Additionally, the energy storage capacity is observed to increase in the same order with the double-branched design storing the highest at ∼ 3600 kJ. Next, the combined effects of the most efficient double-branched fin design and Al2O3 nanoparticles on melting performance are assessed. An addition of 1%, 5% and 10% nanoparticles by volume in the PCM results in an additional time savings of 11.5%, 19.2% and 26.8%, respectively, taking pure PCM case as the reference. The corresponding energy storage, however, is seen to decrease with an increase in the nanoparticles concentration.

Carbon Dioxide Removal Policy in the Making: Assessing Developments in 9 OECD Cases

Abstract: Since the adoption of the Paris Agreement in 2015, spurred by the 2018 IPCC Special Report on Global Warming of 1.5°C, net zero emission targets have emerged as a new organizing principle of climate policy. In this context, climate policymakers and stakeholders have been shifting their attention to carbon dioxide removal (CDR) as an inevitable component of net zero targets. The importance of CDR would increase further if countries and other entities set net-negative emissions targets. The scientific literature on CDR governance and policy is still rather scarce, with empirical case studies and comparisons largely missing. Based on an analytical framework that draws on the multi-level perspective of sociotechnical transitions as well as existing work on CDR governance, we gathered and assessed empirical material until early 2021 from 9 Organisation for Economic Cooperation and Development (OECD) cases: the European Union and three of its Member States (Ireland, Germany, and Sweden), Norway, the United Kingdom, Australia, New Zealand, and the United States. Based on a synthesis of differences and commonalities, we propose a tripartite conceptual typology of the varieties of CDR policymaking: 1) incremental modification of existing national policy mixes, 2) early integration of CDR policy that treats emission reductions and removals as fungible, and 3) proactive CDR policy entrepreneurship with support for niche development. Although these types do not necessarily cover all dimensions relevant for CDR policy and are based on a limited set of cases, the conceptual typology might spur future comparative work as well as more fine-grained case-studies on established and emerging CDR policies.