Research of the surge voltage protection by means of Hybrid Real-Time Power System Simulator

The article considers the simulation of surge voltage protection. A functional diagram of this protection model and the means by which the researches were made are presented. The results are the oscillograms of the surge voltage protection operation for the generator

Bi-Functional Iron-Only Electrodes for Efficient Water Splitting with Enhanced Stability through in Situ Electrochemical Regeneration

Scalable and robust electrocatalysts are required for the implementation of water splitting technologies as a globally applicable means of producing affordable renewable hydrogen. We demonstrate herein that iron-only electrode materials prove to be active for catalyzing both proton reduction and water oxidation in alkaline electrolyte solution with superior activity to that of previously established bi-functional catalysts containing less abundant elements. The reported bi-functionality of the iron electrodes is reversible upon switching of the applied bias through electrochemical interconversion of catalytic species at the electrode surface. Cycling of the applied bias results in in-situ electrochemical regeneration of the catalytic surfaces and thereby extends the catalyst stability and lifetime of the water electrolyzer. Full water splitting at a current density of I = 10 mA cm⁻² is achieved at a bias of approximately 2 V which is stable over at least 3 days (72 one hour switching cycles). Thus, potential-switching is established as a possible strategy of stabilizing electrode materials against degradation in symmetrical water splitting systems.The author’s thank the Oppenheimer Fund (University of Cambridge), the EPSRC (Grant EP/H00338X/2), the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and National Foundation for Research, Technology and Development) and OMV Group for financial support. We also thank the National EPSRC XPS User’s Service (NEXUS) at Newcastle University, UK, where XPS spectra were obtained. Dr Chia-Yu Lin is acknowledged for his invaluable help in initial experiments.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/aenm.20150209

The role of reactive reaction intermediates in two-step heterogeneous electro-catalytic reactions: A model study

Experimental investigations of heterogeneous electrocatalytic reactions have been performed in flow cells which provide an environment with controlled parameters. Measurements of the oxygen reduction reaction in a flow cell with an electrode consisting of an array of Pt nanodisks on a glassy carbon substrate exhibited a decreasing fraction of the intermediate $H_2O_2$ in the overall reaction products with increasing density of the nanodiscs. A similar result is true for the dependence on the catalyst loading in the case of a supported Pt/C catalyst thin-film electrode, where the fraction of the intermediate decreases with increasing catalyst loading. Similar effects have been detected for the methanol oxidation. We present a model of multistep heterogeneous electrocatalytic oxidation and reduction reactions based on an adsorption-reaction-desorption scheme using the Langmuir assumption and macroscopic transport equations. A continuum based model problem in a vertical cross section of a rectangular flow cell is proposed in order to explain basic principles of the experimental situation. It includes three model species A, B, C, which undergo adsorption and desorption at a catalyst surface, as well as adsorbate reactions from A to B to C. These surface reactions are coupled with diffusion and advection in the Hagen Poiseuille flow in the flow chamber of the cell. Both high velocity asymptotic theory and a finite volume numerical are used to obtain approximate solutions to the model. Both approaches show a behaviour similar to the experimentally observed. Working in more general situations, the finite volume scheme was applied to a catalyst layer consisting of a number of small catalytically active areas corresponding to nanodisks. Good qualitative agreement with the experimental findings was established for this case as well

The relationship between spectral and plant diversity: Disentangling the influence of metrics and habitat types at the landscape scale

Biodiversity monitoring is crucial for ecosystem conservation, but ground data collection is limited by cost, time, and scale. Remote sensing is a convenient approach providing frequent, near-real-time information with fine resolution over wide areas. According to the Spectral Variation Hypothesis (SVH), spectral diversity (SD) is an effective proxy of environmental heterogeneity, which ultimately relates to plant diversity. So far, studies testing the relationship between SD and biodiversity have reported contradictory findings, calling for a thorough investigation of the key factors (i.e., metrics applied, habitat type, scale, and temporal effects) and conditions under which such a relationship exists. This study investigates the applicability of the SVH for monitoring plant diversity at the landscape scale by comparing the performance of three types of SD metrics. Species richness and functional diversity were calculated for >2000 grid cells of 5 ' x 3 ' covering the Czech Republic. Within each cell, we quantified SD using a Landsat-8 "greenest pixel" composite by applying (i) the standard deviation of NDVI, (ii) Rao's Q entropy index and (iii) the richness of "spectral communities". Habitat type (i.e., land cover) was included in the models of the relationship between SD and ground biodiversity. Both species richness and functional diversity showed positive and significant relationships with each SD metric tested. However, SD alone accounted for a small fraction of the deviance explained by the models. Furthermore, the strength of the relationship depended significantly on habitat type and was highest in natural areas with transitional bushy and herbaceous vegetation. Our results underline that despite the stability of the significance of the relationship between SD and plant diversity at this scale, the applicability of SD for biodiversity monitoring is contextdependent and the factors mediating such a relationship must be carefully considered to avoid misleading conclusions

Climate change litigation: a review of research on courts and litigants in climate government

Studies of climate change litigation have proliferated over the past two decades, as lawsuits across the world increasingly bring policy debates about climate change mitigation and adaptation, as well as climate change‐related loss and damage to the attention of courts. We systematically identify 130 articles on climate change litigation published in English in the law and social sciences between 2000 and 2018 to identify research trajectories. In addition to a budding interdisciplinarity in scholarly interest in climate change litigation we also document a growing understanding of the full spectrum of actors involved and implicated in climate lawsuits and the range of motivations and/or strategic imperatives underpinning their engagement with the law. Situating this within the broader academic literature on the topic we then highlight a number of cutting edge trends and opportunities for future research. Four emerging themes are explored in detail: the relationship between litigation and governance; how time and scale feature in climate litigation; the role of science; and what has been coined the “human rights turn” in climate change litigation. We highlight the limits of existing work and the need for future research—not limited to legal scholarship—to evaluate the impact of both regulatory and anti‐regulatory climate‐related lawsuits, and to explore a wider set of jurisdictions, actors and themes. Addressing these issues and questions will help to develop a deeper understanding of the conditions under which litigation will strengthen or undermine climate governance. This article is categorized under: Policy and Governance > Multilevel and Transnational Climate Change Governanc

Accuracy versus precision in boosted top tagging with the ATLAS detector

The identification of top quark decays where the top quark has a large momentum transverse to the beam axis, known as top tagging, is a crucial component in many measurements of Standard Model processes and searches for beyond the Standard Model physics at the Large Hadron Collider. Machine learning techniques have improved the performance of top tagging algorithms, but the size of the systematic uncertainties for all proposed algorithms has not been systematically studied. This paper presents the performance of several machine learning based top tagging algorithms on a dataset constructed from simulated proton-proton collision events measured with the ATLAS detector at √s = 13 TeV. The systematic uncertainties associated with these algorithms are estimated through an approximate procedure that is not meant to be used in a physics analysis, but is appropriate for the level of precision required for this study. The most performant algorithms are found to have the largest uncertainties, motivating the development of methods to reduce these uncertainties without compromising performance. To enable such efforts in the wider scientific community, the datasets used in this paper are made publicly available

Studies of the Energy Dependence of Diboson Polarization Fractions and the Radiation-Amplitude-Zero Effect in WZ Production with the ATLAS Detector

: This Letter presents the first study of the energy dependence of diboson polarization fractions in WZ→lνl^{'}l^{'}(l,l^{'}=e,μ) production. The dataset used corresponds to an integrated luminosity of 140 fb^{-1} of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector. Two fiducial regions with an enhanced presence of events featuring two longitudinally polarized bosons are defined. A nonzero fraction of events with two longitudinally polarized bosons is measured with an observed significance of 5.3 standard deviations in the region with 100200 GeV, where p_{T}^{Z} is the transverse momentum of the Z boson. This Letter also reports the first study of the radiation-amplitude-zero effect. Events with two transversely polarized bosons are analyzed for the ΔY(l_{W}Z) and ΔY(WZ) distributions defined respectively as the rapidity difference between the lepton from the W boson decay and the Z boson and the rapidity difference between the W boson and the Z boson. Significant suppression of events near zero is observed in both distributions. Unfolded ΔY(l_{W}Z) and ΔY(WZ) distributions are also measured and compared to theoretical predictions

Combination of searches for heavy spin-1 resonances using 139 fb−1 of proton-proton collision data at s = 13 TeV with the ATLAS detector

A combination of searches for new heavy spin-1 resonances decaying into different pairings of W, Z, or Higgs bosons, as well as directly into leptons or quarks, is presented. The data sample used corresponds to 139 fb−1 of proton-proton collisions at = 13 TeV collected during 2015–2018 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting quark pairs (qq, bb, , and tb) or third-generation leptons (τν and ττ) are included in this kind of combination for the first time. A simplified model predicting a spin-1 heavy vector-boson triplet is used. Cross-section limits are set at the 95% confidence level and are compared with predictions for the benchmark model. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The complementarity of the various analyses increases the sensitivity to new physics, and the resulting constraints are stronger than those from any individual analysis considered. The data exclude a heavy vector-boson triplet with mass below 5.8 TeV in a weakly coupled scenario, below 4.4 TeV in a strongly coupled scenario, and up to 1.5 TeV in the case of production via vector-boson fusion