Search

We present observations from X-ray to mid-infrared wavelengths of the most energetic non-quasar transient ever observed, AT2021lwx. Our data show a single optical brightening by a factor $>100$ to a luminosity of $7\times10^{45}$ erg s$^{-1}$, and a total radiated energy of $1.5\times10^{53}$ erg, both greater than any known optical transient. The decline is smooth and exponential and the ultra-violet - optical spectral energy distribution resembles a black body with temperature $1.2\times10^4$ K. Tentative X-ray detections indicate a secondary mode of emission, while a delayed mid-infrared flare points to the presence of dust surrounding the transient. The spectra are similar to recently discovered optical flares in known active galactic nuclei but lack some characteristic features. The lack of emission for the previous seven years is inconsistent with the short-term, stochastic variability observed in quasars, while the extreme luminosity and long timescale of the transient disfavour the disruption of a single solar-mass star. The luminosity could be generated by the disruption of a much more massive star, but the likelihood of such an event occurring is small. A plausible scenario is the accretion of a giant molecular cloud by a dormant black hole of $10^8 - 10^9$ solar masses. AT2021lwx thus represents an extreme extension of the known scenarios of black hole accretion., 11 pages, 5 figures, Accepted for publication in MNRAS

Purpose Despite its well-founded criticism and lack of proper justification under core saturation conditions, the T-equivalent transformer model (Steinmetz scheme) is obviously championing in the literature. This educational paper aims to explain in a simple manner the limitations of the T-model of a low-frequency transformer and critically analyses some attempts to improve it. Design/methodology/approach Using a simplified examination of magnetic fluxes in the core and windings and using the modeling in ATPDraw, it is shown that transient transformer models with the indivisible leakage inductance allow circumventing the drawbacks of the T-model. Findings The authors show the absence of valid grounds for subdividing the leakage inductance of a transformer between its primary and secondary windings. The connection between the use of individual leakage inductances and inaccurate prediction of inrush current peaks is outlined as an important example. Practical implications The presented models can be used either as independent tools or serve as a reference for subsequent developments. Social implications Over generations, the habitual transformer T-equivalent is widely used by engineers and Electromagnetic Transients Program experts with no attention to its inadequacy under core saturation conditions. Having studied typical winding configurations, the authors have shown that neither of them has any relation to the T-equivalent. Originality/value This educational paper will contribute to the correct understanding of the transients occurring in a transformer under abnormal conditions such as inrush current or ferroresonance events, as well as during an out-of-phase synchronization of step-up generator transformers.

Talk given at the conference

The dispersion measure (DM) of fast radio bursts (FRBs) provides a unique way to probe ionised baryons in the intergalactic medium (IGM). Cosmological models with different parameters lead to different DM-redshift ($\mathrm{DM}-z$) relations. Additionally, the over/under-dense regions in the IGM and the circumgalactic medium of intervening galaxies lead to scatter around the mean $\mathrm{DM}-z$ relations. We have used the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations to measure the mean $\mathrm{DM}-z$ relation and the scatter around it using over one billion lines-of-sight between redshifts $0, Comment: Submitted to MNRAS. 14 pages, 15 figures, Comments Welcome. Data and model will be released upon being accepted

Analyses of transient dynamics are critical to understanding infectious disease transmission and persistence. Identifying and predicting transients across scales, from within-host to community-level patterns, plays an important role in combating ongoing epidemics and mitigating the risk of future outbreaks. Moreover, greater emphases on non-asymptotic processes will enable timely evaluations of wildlife and human diseases and lead to improved surveillance efforts, preventive responses, and intervention strategies. Here, we explore the contributions of transient analyses in recent models spanning the fields of epidemiology, movement ecology, and parasitology. In addition to their roles in predicting epidemic patterns and endemic outbreaks, we explore transients in the contexts of pathogen transmission, resistance, and avoidance at various scales of the ecological hierarchy. Examples illustrate how (i) transient movement dynamics at the individual host level can modify opportunities for transmission events over time; (ii) within-host energetic processes often lead to transient dynamics in immunity, pathogen load, and transmission potential; (iii) transient connectivity between discrete populations in response to environmental factors and outbreak dynamics can affect disease spread across spatial networks; and (iv) increasing species richness in a community can provide transient protection to individuals against infection. Ultimately, we suggest that transient analyses offer deeper insights and raise new, interdisciplinary questions for disease research, consequently broadening the applications of dynamical models for outbreak preparedness and management. Supplementary information The online version contains supplementary material available at 10.1007/s12080-021-00514-w.

D.M. and H.D. thank the Israel Science Foundation (Contract No. 641/18) and the National Natural Science Foundation of China (Grant No. 21904143) for financial support. P.P. and S.M. are grateful for the financial support from the Swiss National Science Foundation under Grant Ambizione Energy 160553. P.P. also gratefully acknowledges the Academy Research Fellow funding (Grant No. 315739) and project funding (Grant No. 334828) from the Academy of Finland. E.S. is grateful to the Development Program of Lomonosov Moscow State University and the Russian Science Foundation (Grant No. 19-13-00283). H.H.G. acknowledges the Swiss National Science Foundation grants: 200021_175745 “Photo Induced Charge Transfer Reaction at Molecular Interfaces: towards new routes of solar energy storage” and 20SC-1_193608 “Photoproduction of hydrogen in biphasic systems with electron donor recycling (PHOTO2H)”. Emulsification of immiscible two-phase fluids, i.e., one condensed phase dispersed homogeneously as tiny droplets in an outer continuous medium, plays a key role in medicine, food, chemical separations, cosmetics, fabrication of micro- and nanoparticles and capsules, and dynamic optics. Herein, we demonstrate that water clusters/droplets can be formed in an organic phase via the spontaneous assembling of ionic bilayers. We term these clusters ionosomes, by analogy with liposomes where water clusters are encapsulated in a bilayer of lipid molecules. The driving force for the generation of ionosomes is a unique asymmetrical electrostatic attraction at the water/oil interface: small and more mobile hydrated ions reside in the inner aqueous side, which correlate tightly with the lipophilic bulky counterions in the adjacent outer oil side. These ionosomes can be formed through electrochemical (using an external power source) or chemical (by salt distribution) polarization at the liquid–liquid interface. The chargedensity of the cations, the organic solvent, and the synergistic effects between tetraethylammonium and lithium cations, all affecting the formation of ionosomes, were investigated. These results clearly prove that a new emulsification strategy is developed providing an alternative and generic platform, besides the canonical emulsification procedure with either ionic or nonionic surfactants as emulsifiers. Finally, we also demonstrate the detection of individual ionosomes via single-entity electrochemistry.

Purpose. Development of methods and algorithms for calculation of starting modes of the induction motors with the squirrel-cage rotor. Methodology. Mathematical modelling of starting modes of asynchronous electric drives in various coordinate systems with the use of numerical methods for solving boundary problems for systems of differential equations and nonlinear systems of final equations and calculation with their use of static characteristics. Results. Methods and algorithms for numerical analysis of the starting modes of asynchronous electric drive have been developed, which make it possible to calculate the static characteristics and transients in fixed three-phase and orthogonal two-phase coordinate systems. Academic novelty. Known in the literature methods of calculation of starting modes have in their basis classical equivalent circuits with different approximate methods of calculating the parameters taking into account the saturation of a magnetic core and current displacement in a rotor winding. This approach requires a special solution of the adequacy problem for each problem. The methods described in the article for the saturation accounting use real magnetization characteristics of the main magnetic flux and leakage fluxes separately, and the skin effect phenomenon is taken into account by representing the squirrel-cage rotor winding as multilayer. Such mathematical model of the motor is universal and makes it possible to take into account the saturation and current displacement in any dynamic mode, including the start-up process. Mathematical models developed on the basis of the proposed methods provide the adequacy of results with a minimum amount of calculations and make it possible to perform optimization calculations. Practical value. Created on the basis of developed algorithms calculation programs allow to carry out with high reliability calculation of starting modes both in three-phase and two-phase axes of coordinates that gives the chance to analyze not only symmetric, but also asymmetric modes and to predict special features of functioning of system of the electric drive in the set technological conditions of operation and to form requirements to development and adjustment of starting systems with the purpose of maintenance of power effective and reliable operation of system of asynchronous electric drives., Розроблено методи і алгоритми числового аналізу пускових режимів асинхронного електроприводу, які дають змогу розраховувати статичні характеристики і перехідні процеси з урахуванням насичення магнітопроводу і явища скін-ефекту в стержнях ротора. Математичною основою розроблених алгоритмів є проекційний метод розв’язування нелінійних крайових задач, метод продовження по параметру, метод Ньютона розв’язування нелінійних систем рівнянь, числового інтегрування нелінійних систем диференціальних рівнянь. Розроблені математичні моделі дають змогу здійснювати з високою достовірністю розрахунок пускових режимів у трифазних і двофазних координатних осях, що дає змогу аналізувати не тільки симетричні, але й несиметричні режими і прогнозувати особливості функціонування системи асинхронного електроприводу в заданих технологічних умовах експлуатації.

This article presents a novel waveform relaxation scheme to solve electromagnetically large structures loaded with lumped linear and nonlinear elements. The scheme partitions the problem into a linear electromagnetic structure and a possibly nonlinear lumped circuit, which are coupled using Thévenin interfaces across the steps of an iterative waveform relaxation scheme. The main novel contribution is an adaptive selection of the decoupling resistances used as port references to define incident and reflected scattering signals, whose time-domain samples are refined through iterations. The decoupling resistances are updated through iterations, with the main objective of improving convergence speed and ultimately runtime. The resulting scheme is self-adapting to terminations exploiting high dynamic range in their impedance profiles and is able to provide a suboptimal convergence rate. Three-dimensional shielding structures loaded with nonlinear elements are employed as numerical examples to demonstrate the proposed method.

International audience; Reusable liquid-propellant rocket engines (LPREs) imply more demanding robustness requirements than expendable ones due to their extended capabilities. Therefore, the goal of this work was to develop a control loop adapted to all the operating phases of LPRE, including transients, and robust to internal parametric variations. Firstly, thermo-fluid-dynamic simulators representative of the gas-generator-cycle engines were built. These simulators were subsequently translated into nonlinear state-space models. Based on these models, the continuous subphase of the start-up transient is controlled to track precomputed reference trajectories. Beyond the start-up, throttling scenarios are managed with end-state-tracking algorithm. Model Predictive Control has been applied in a linearised manner with robustness considerations to both scenarios, in which a set of hard state and control constraints must be respected. Tracking of pressure (thrust) and mixture-ratio operating points within the design envelope is achieved in simulation while respecting constraints. Robustness to variations in the predominant parameters, to external state perturbations and to the possible impact of an observer on the loop, is demonstrated.

Supersoft X-ray sources (SSS) have been identified as white dwarfs accreting from binary companions and undergoing nuclear-burning of the accreted material on their surface. Although expected to be a relatively numerous population from both binary evolution models and their identification as Type Ia supernova progenitor candidates, given the very soft spectrum of SSSs relatively few are known. Here we report on the X-ray and optical properties of 1RXS J050526.3-684628, a previously unidentified accreting nuclear-burning white dwarf located in the Large Magellanic Cloud (LMC). XMM-Newton observations enabled us to study its X-ray spectrum and measure for the first time short period oscillations of ~170 s. By analysing newly obtained X-ray data by eROSITA, together with Swift observations and archival ROSAT data, we have followed its long-term evolution over the last 3 decades. We identify 1RXS J050526.3-684628 as a slowly-evolving post-nova SSS undergoing residual surface nuclear-burning, which finally reached its peak in 2013 and is now declining. Though long expected on theoretical grounds, such long-lived residual-burning objects had not yet been found. By comparison with existing models, we find that the effective temperature and luminosity evolution are consistent with a ~0.7 $M_{\odot}$ carbon-oxygen white dwarf accreting ~10$^{-9}~\rm{M}_{\odot}$/yr. Our results suggest there may be many more undiscovered SSSs and "missed" novae awaiting dedicated deep X-ray searches in the LMC and elsewhere., Comment: 9 pages, 4 figures, accepted for publication in MNRAS

The article deals with the flux linkages estimation of a synchronous motor during either speed or load transients. The nonlinear magnetic model is obtained by a radial basis function neural network (NN), which yields a differentiable function as link among currents and flux linkages. As a distinctive feature, the training of the NN is performed by an innovative algorithm that operates both at steady state and during speed and load transients. The method has been validated experimentally by several tests performed on different synchronous reluctance and interior permanent magnet motor drives.

Power transients faults on high voltage lines are prominently due to high frequency transients. These transients affect the predicted life and efficiency of equipment. The Fast Fourier Transform (FFT) is helpful in analysing the effect of high frequencies and Frequency Response Analysis (FRA) provide support in diagnosis and detection of deformation in a transformers. The major aim of this study is to analyse the incorporation of frequencies based on resonating core of a particular transformer. Using transfer function method an impedance change in transformer has been observed when equipment is subjected to high voltage transients. The effect of change in impedance is that it degrade the life of a core with respect to time. In this paper, research that has been done already on Transformers of different ratings i.e. 100, 50 and 30 kVA are studied and then an experiment is performed on 50-kVA transformer. It was concluded that the core of a transformer having rating equal or less than 50 kVA practically shows single resonance behavior while above 50 kVA for instance 100-kVA transformer core resonates twice. In actual, result defines the core deviating frequency with respect to the rating of a transformer.

Temporal variations in the chemistry of infiltrating water into the subsurface are known to cause remobilization of colloids from the grain surfaces, thereby increasing the travel distance of the colloidal contaminants. Hence, it is essential to thoroughly understand the transport, deposition, and release mechanisms of colloids in the subsurface, through laboratory experiments and modeling. There are only a few experiments in which the chemistry of inflow water is changed rapidly during colloid transport. Also, although some models have been presented for simulating the effect of transient chemistry on the fate of colloids, there is no consensus in this regard, as the proposed models suffer from shortcomings. In this study, we systematically investigated the effect of temporal variations in ionic strength on the remobilization of deposited colloids in saturated porous media through laboratory column experiments and numerical modeling. Four sets of column experiments were performed, in which we injected carboxylate-modified latex colloids at a given ionic strength for a specified period. After breakthrough of colloids, the ionic strength of inflowing water was decreased in a stepwise manner to 0 mM (DI water). The initial ionic strength values of the four experiments were 100, 50, 25, and 10 mM. We observed partial release of deposited colloids after several steps of ionic strength decrease with significant release observed only when the ionic strength was reduced to below 10 mM. We also found that the fraction of released colloids decreased with increasing value of initial ionic strength of inflow water. We have developed a mathematical model incorporating a novel formulation for ionic strength-dependent deposition and release. The model is found to capture the colloid breakthrough curves reasonably well for all experiments with the same set of parameter values, except the one at the initial ionic strength of 25 mM.

The presence of DC grids in distribution networks is being increased nowadays and is expected to be quite relevant in a near future, due to several advantages compared to traditional AC systems. Regardless of this, Power Quality in DC grids (DC PQ) (voltage variations, transients, spectral components, etc.) still remains not properly considered and there is a lack of reference normative documents such as standards, application guides or technical reports for their application. In this context, it is necessary to obtain more experience on real measurements, in order to define appropriate DC PQ parameters and limits that assess a reliable operation of the whole power network and eventually lead to establishing a reference frame acceptable for both generation sources and final users. In this work, a novel high frequency (up to 4 MS/s) digitiser system is presented for the study of DC PQ events. The system is designed to acquire waveforms with triggers fired by events in both DC and AC signals. The captured signals are pre-processed in real-time to be able to recover pre-trigger information stored in memory. The system was installed in a real DC micro-grid and configured to take data in an unattended way. Additionally, the results of the first months of data acquisition are presented.

The Pierre Auger Observatory, which is the largest air-shower experiment in the world, offers unprecedented exposure to neutral particles at the highest energies. Since the start of data collection more than 18 years ago, various searches for ultra-high-energy (UHE, E & 1017 eV) photons have been performed, either for a diffuse flux of UHE photons, for point sources of UHE photons or for UHE photons associated with transient events such as gravitational wave events. In the present paper, we summarize these searches and review the current results obtained using the wealth of data collected by the Pierre Auger Observatory., Argentina-Comision Nacional de Energia Atomica, ANPCyT, Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Gobierno de la Provincia de Mendoza, Municipalidad de Malargue, NDM Holdings, Valle Las Lenas, Australian Research Council, Belgium-Fonds de la Recherche Scientifique (FNRS), FWO, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) Fundacao de Apoio a Pesquisa do Distrito Federal (FAPDF) Financiadora de Inovacao e Pesquisa (Finep) Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio De Janeiro (FAPERJ) Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) 2019/10151-2 2010/07359-6 1999/05404-3, Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes (MCTIC), France-Centre de Calcul IN2P3/CNRS Centre National de la Recherche Scientifique (CNRS) Region Ile-de-France Centre National de la Recherche Scientifique (CNRS) Departement Sciences de l'Univers (SDU-INSU/CNRS) French National Research Agency (ANR) LABEX ANR-10-LABX-63 ANR-11-IDEX-0004-02, Federal Ministry of Education & Research (BMBF) German Research Foundation (DFG) Finanzministerium Baden-Wurttemberg Helmholtz Alliance for Astroparticle Physics (HAP) Helmholtz Association Ministerium fur Kultur und Wissenschaft des Landes Nordrhein-Westfalen Ministerium fur Wissenschaft, Forschung und Kunst des Landes Baden-Wurttemberg, Italy-Istituto Nazionale di Fisica Nucleare (INFN) Istituto Nazionale Astrofisica (INAF), Ministry of Education, Universities and Research (MIUR), CETEMPS Center of Excellence, Ministry of Foreign Affairs and International Cooperation (Italy), Consejo Nacional de Ciencia y Tecnologia (CONACyT) 167733 Universidad Nacional Autonoma de Mexico Programa de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT) Universidad Nacional Autonoma de Mexico, Netherlands-Ministry of Education, Culture and Science Netherlands Organization for Scientific Research (NWO), SURF Cooperative, Poland-Ministry of Education and Science DIR/WK/2018/11 National Science Centre, Poland 2016/22/M/ST9/00198 2016/23/B/ST9/01635 2020/39/B/ST9/01398, Portuguese Foundation for Science and Technology FEDER funds within Programa Operacional Factores de Competitividade through FundacAo para a Ciencia e a Tecnologia (COMPETE), Romania-Ministry of Research, Innovation and Digitization, CNCS/CCCDI UEFISCDI within the National Nucleus Program PN19150201/16N/2019 PN1906010 PNCDI III TE128 PN-III-P1-1.1-TE-2021-0924/TE57/2022 PED289, Slovenian Research Agency - Slovenia P1-0031 P1-0385 I0-0033 N1-0111, Spanish Government FPA2017-85114-P PID2019-104676GB-C32, Xunta de Galicia, European Commission ED431C 2017/07, Junta de Andalucia SOMM17/6104/UGR P18-FR-4314, European Commission, RENATA Red Nacional Tematica de Astroparticulas FPA2015-68783-REDT, Maria de Maeztu Unit of Excellence MDM-2016-0692, United States Department of Energy (DOE) DE-AC02-07CH11359 DE-FR02-04ER41300 DE-FG02-99ER41107 DE-SC0011689, National Science Foundation (NSF) 0450696, Grainger Foundation, Marie Curie-IRSES/EPLANET, European Particle Physics Latin American Network, UNESCO, MSMT CR LTT18004 LM2015038 LM2018102 CZ.02.1.01/0.0/0.0/16_013/0001402 CZ.02.1.01/0.0/0.0/18_046/0016010 CZ.02.1.01/0.0/0.0/17_049/0008422

We constrain the Hubble constant H$_0$ using Fast Radio Burst (FRB) observations from the Australian Square Kilometre Array Pathfinder (ASKAP) and Murriyang (Parkes) radio telescopes. We use the redshift-dispersion measure (`Macquart') relationship, accounting for the intrinsic luminosity function, cosmological gas distribution, population evolution, host galaxy contributions to the dispersion measure (DM$_{\rm host}$), and observational biases due to burst duration and telescope beamshape. Using an updated sample of 16 ASKAP FRBs detected by the Commensal Real-time ASKAP Fast Transients (CRAFT) Survey and localised to their host galaxies, and 60 unlocalised FRBs from Parkes and ASKAP, our best-fitting value of H$_0$ is calculated to be $73_{-8}^{+12}$ km s$^{-1}$ Mpc$^{-1}$. Uncertainties in FRB energetics and DM$_{\rm host}$ produce larger uncertainties in the inferred value of H$_0$ compared to previous FRB-based estimates. Using a prior on H$_0$ covering the 67--74 km s$^{-1}$ Mpc$^{-1}$ range, we estimate a median DM$_{\rm host} = 186_{-48}^{+59}$ km s$^{-1}$ Mpc$^{-1}$, exceeding previous estimates. We confirm that the FRB population evolves with redshift similarly to the star-formation rate. We use a Schechter luminosity function to constrain the maximum FRB energy to be $\log_{10} E_{\rm max}=41.26_{-0.22}^{+0.27}$ erg assuming a characteristic FRB emission bandwidth of 1 GHz at 1.3 GHz, and the cumulative luminosity index to be $\gamma=-0.95_{-0.15}^{+0.18}$. We demonstrate with a sample of 100 mock FRBs that H$_0$ can be measured with an uncertainty of $\pm 2.5$ km s$^{-1}$ Mpc$^{-1}$, demonstrating the potential for clarifying the Hubble tension with an upgraded ASKAP FRB search system. Last, we explore a range of sample and selection biases that affect FRB analyses., Comment: 21 pages, 19 figures, 6 tables, accepted by MNRAS, updated Table 5 and Figure 5

The study of flaring astrophysical events in the multi-messenger approach requires instantaneous follow-up observations to better understand the nature of these events through complementary observational data. We present Astro-COLIBRI as a platform that integrates specific tools in the real-time multi-messenger ecosystem. The Astro-COLIBRI platform bundles and evaluates alerts about transients from various channels. It further automates the coordination of follow-up observations by providing and linking detailed information through its comprehensible graphical user interface. We present the functionalities with documented examples of Astro-COLIBRI usage through the community since its public release in August 2021. We highlight the use cases of Astro-COLIBRI for planning follow-up observations by professional and amateur astronomers, as well as checking predictions from theoretical models., Accepted in Galaxies; Platform website: www.astro-colibri.com

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

Recently in the WWR-K water-water research reactor the former HEU fuel, enriched to 36% in Uranium235, was changed to LEU one, enriched to 19.7%, with substantial change of the core configuration. In view of reactor conversion, a new Safety Analysis Report (SAR) was developed for the WWR-K reactor. Substantiation of reactor safe operation under both normal operation and emergency conditions was done under thermal-hydraulic approach. In the analysis developed prior to physical start up it was assumed that a main circulation pump (MCP) provides the coolant flow rate in the core equal to 350 m 3/h (a certified value for the pump CB-321). However, in course of the reactor physical start up it was found that it is only 250 m 3/h. The reason was a decision of the reactor staff to reduce the primary pump power consumption, prolonging its life time.Therefor the thermal hydraulic analysis was revised, and the SAR was renewed. Safety analysis implies also consideration of some potential initiating events capable to develop into an accident. So, several typical initiating events are subject to thermal-hydraulic analysis to substantiate observance of nuclear and radiation safety in emergency situations. It is shown that, owing to proper operation of safety systems, the initiating events under consideration don’t result into accidents, if two primary pumps provide not more than 585 m 3/h.

We conduct searches for γ-ray emission from the binary black-hole (BBH) mergers reported in the Gravitational-Wave Candidate Event Database (GraceDB). The γ-ray data are from the all-sky survey of the Large-Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope (Fermi), which allows searches for events of given time durations in large sky areas. The Two-Micron All-Sky Survey Photometric Redshift Catalog (2MPZ) is used for target selection, from which galaxy sources within the 90% credible areas and the distance ranges given by the gravitational-wave (GW) detections are determined. Excluding those BBH cases with large credible areas and/or dense fields (containing too many 2MPZ sources), searches for short transient events over the time duration of from −1 to 100 days of a trigger time for seven BBH mergers are conducted. We find two candidate short flaring events in the field of the GW event S200311bg and one in that of S190408an. However, the flaring events all have low significance (after considering the trial factor), and the third one appears off the position of the target galaxy. We discuss one of them from the first field that is detected in different short time-bin data and suggest that it is possibly a real flare arising from a radio galaxy. More such studies for the near-future GW detection run are planned, for which we will adjust our search strategy to be more effective and target flares of various time scales.

This paper provides the first comprehensive study on the forward and reverse conduction and reliability performance of the Gallium Nitride (GaN) and Silicon Carbide (SiC) power cascode devices, in comparison with standard silicon & SiC power MOSFETs and the silicon superjunction MOSFETs. The impact of temperature and the external gate resistance are investigated, and a practical yet accurate analytical model has been developed to calculate the switching rate of cascode devices. The 3rd quadrant operation devices through the body diodes is also studied along with unclamped switching properties for avalanche breakdown limits of GaN and SiC cascodes.

Common ravens (Corvus corax; ravens) are a behaviorally flexible nest predator of several avian species, including species of conservation concern. Movement patterns based on life history phases, particularly territoriality of breeding birds and transiency of nonbreeding birds, are thought to influence the frequency and efficacy of nest predation. As such, predicting where on the landscape territorial resident and non-territorial transient birds may be found in relation to the distribution of sensitive prey is of increasing importance to managers and conservationists. From 2007 to 2019, we conducted raven point count surveys between mid-March and mid-September across 43 different field sites representing typical sagebrush (Artemisia spp.) ecosystems of the Great Basin, USA. The surveys conducted during 2007–2016 were used in previously published maps of raven occurrence and density. Here, we examined the relationship between occurrence and density of ravens using spatially explicit predictions from 2 previously published studies and differentiate areas occupied by higher concentrations of resident ravens as opposed to transients. Surveys conducted during 2017–2019 were subsequently used to evaluate the predicted trends from our analytical approach. Specifically, we used residuals from a generalized linear regression to establish the relationship between occurrence and density, which ultimately resulted in a spatially explicit categorical map that identifies areas of resident versus transient ravens. We evaluated mapped categories using independently collected observed raven group sizes from the 2017–2019 survey data, as well as an independent dataset of global positioning system locations of resident and transient individuals monitored during 2019–2020. We observed moderate agreement between the mapped categories and independent datasets for both evaluation approaches. Our map provides broad inference about spatial variation in potential predation risk from ravens for species such as greater sage-grouse (Centrocercus urophasianus) and can be used as a valuable spatial layer for decision support tools aimed at guiding raven management decisions and, ultimately, improving survival and reproduction of sensitive prey within the Great Basin.

SOXS (Son Of X-Shooter) is a single object spectrograph, characterized by offering a wide simultaneous spectral coverage from U- to H-band, built by an international consortium for the 3.6-m ESO New Technology Telescope at the La Silla Observatory, in the Southern part of the Chilean Atacama Desert. The consortium is focussed on a clear scientific goal: the spectrograph will observe all kind of transient and variable sources discovered by different surveys with a highly flexible schedule, updated daily, based on the Target of Opportunity concept. It will provide a key spectroscopic partner to any kind of imaging survey, becoming one of the premier transient follow-up instruments in the Southern hemisphere. SOXS will study a mixture of transients encompassing all distance scales and branches of astronomy, including fast alerts (such as gamma-ray bursts and gravitational waves), mid-term alerts (such as supernovae and X-ray transients), and fixed-time events (such as the close-by passage of a minor planet or exoplanets). It will also have the scope to observe active galactic nuclei and blazars, tidal disruption events, fast radio bursts, and more. Besides of the consortium programs on guaranteed time, the instrument is offered to the ESO community for any kind of astrophysical target. The project has passed the Final Design Review and is currently in manufacturing and integration phase. This paper describes the development status of the project., Proc SPIE Volume 11447, Ground-based and Airborne Instrumentation for Astronomy VIII, 1144709,2020

Disturbances resulting from switching operations, failures, lightning strikes or loads variations can cause abnormal currents and voltages dangerous for the equipment and the analysis and evaluation of the latter is essential for the reliability of the system [1], [2]. The conventional HV networks are built mainly as overhead, but the progressive increase in the share of cable lines leads to significant topological and parametric changes in the network, and hence its behaviour during transients. Ensuring the reliable and safe operation of the equipment requires the study of the current and the phenomena encountered during transients in networks with a large share of cables. This paper presents a study and analysis of some phenomena caused by switching operations in a real HV electrical network, part of the electric power system. For the purposes of comparison, the paper also represents some transient phenomena typical for overhead lines (OHL) although they are widely studied. The studies were performed in ATP-EMTP.

International audience; Classification of transients is a difficult task. In bioacoustics, almost all studies are still done with human labeling. In passive acoustic monitoring (PAM), the data to label are made up from months of continuous recordings with multiple recording stations and the time required to label everything with human labeling is longer than the next recording session will take to produce new data, even with multiple experts. To help lay a foundation for the emergence of automatic labeling of marine mammal transients, we built a dataset using weak labels from a 3TB dataset of marine mammal transients of DCLDE 2018. The DCLDE dataset was made for a click classification challenge. The new dataset has strong labels and opened a new challenge, DOCC10, whose baseline is also described in this paper. The accuracy of 71% of the baseline is already good enough to curate the large dataset, leaving only some regions of interest still to be expertised. But this is far from perfect, and there remains space for future improvement, or challenging alternative techniques. A smaller version of DOCC10 named DOCC7 is also presented.

Radio observations of tidal disruption events (TDEs) probe material ejected by the disruption of stars by supermassive black holes (SMBHs), uniquely tracing the formation and evolution of jets and outflows, revealing details of the disruption hydrodynamics, and illuminating the environments around previously-dormant SMBHs. To date, observations reveal a surprisingly diverse population. A small fraction of TDEs (at most a few percent) have been observed to produce radio-luminous mildly relativistic jets. The remainder of the population are radio quiet, producing less luminous jets, non-relativistic outflows or, possibly, no radio emission at all. Here, we review the radio observations that have been made of TDEs to date and discuss possible explanations for their properties, focusing on detected sources and, in particular, on the two best-studied events: Sw J1644+57 and ASASSN-14li. We also discuss what we have learned about the host galaxies of TDEs from radio observations and review constraints on the rates of bright and faint radio outflows in TDEs. Upcoming X-ray, optical, near-IR, and radio surveys will greatly expand the sample of TDEs, and technological advances open the exciting possibility of discovering a sample of TDEs in the radio band unbiased by host galaxy extinction., Resubmitted for publication in Springer Space Science Reviews following referee comments. Chapter in ISSI review "The Tidal Disruption of Stars by Massive Black Holes" vol. 79. Table 2 is available in machine-readable format upon request

When an unloaded converter transformer is being energised, large inrush current may flow in the voltage jump side depending upon the residual flux in the core and the closing voltage angle of the power grid due to the hysteresis characteristics of the core, causing false operation of protective relays and bringing many adverse effects to the grid and primary electrical devices. Based on the analysis of the elimination of inrush current using controlled switching, the phase-to-phase electromagnetic coupling relationship which would be influenced by the core structure and winding connection mode was taken into account when considering the controlled switching strategy of three-phase transformer. With the analysis of core residual flux after de-energisation and the dynamic magnetisation of core during the energisation, a controlled switching strategy for inrush current restraining when energising converter transformer is presented in this study. Only the current arc quenching sequence during circuit breaker opening and the voltage extinguishing phase angle are asked for this strategy, and the simulation by electromagnetic transients programme and the experiment results indicate that this strategy could restrain the inrush transient efficiently.

Very fast transient over voltage (VFTO) is a unique electromagnetic transient phenomenon occurring in Gas Insulated Substation (GIS), which determines the insulation level of the GIS (above 330 kV). Unfortunately, up to the present, there is no standard VFTO waveform to test the high voltage equipment to ensure the safety of power grid. For this reason, this paper focuses on obtaining the standard VFTO waveform through finding a method to fit the curve of VFTO. Hence, a UHV disconnector operation experiment of GIS was carried out on the UHV GIS test platform. The representative waveform of VFTO generated by a single SF6 gas discharge was extracted from the measured data. Furthermore, The Fast Fourier Transformer is applied to analyze the frequency features of VFTO. As one of the switchgear operation voltage, VFTO can be concluded to be a superposition of the power-frequency waveform with the non-periodic impulse waveform. Thus, it is found that The Squares Method is convenient for fitting the expression of VFTO according to its transient characteristics. Then the standard VFTO waveform can be obtained from the fitting expression, which coincides well with the measured waveform. The simulation results using ATP-EMTP software are compared with the calculation results and the measured results.

Entrapped air blocking the flow in pipeline systems is a common cause of increased pumping costs. At present, air is generally removed via valves or pipeline excavation and drilling. This b...

Non-linear loads can cause transients in electronic switches. They also result in a fluctuating output when the device is switched ON or OFF. These transients can harm not only the switches but also the devices that they are connected to, by passing excess currents or voltages to the devices. By applying machine learning, we can improve the gate drive voltages of the switches and thereby reduce switch transients. A feedback system is built that measures the output transients and then feeds it to a neural network algorithm that then gives a proper gate drive to the device. This will reduce transients and also improve performances of switch based devices like inverters and converters.

Codes and methods are subjected to a continuous update process for answering the regulatory requirements concerning the long-term operation of existing reactors and new concept deployment. In this continuous improvement process, new generation codes are developed for supporting industrial applications and the long-term strategy. In this paper, attention is devoted to selecting codes under development in France for lattice and core steady-state and transient calculations. These codes, APOLLO3® and CATHARE3, have been selected for carrying out the activities of the H2020 CAMIVVER Project oriented to the 3D-multiphysics couplings improvements. Multiscale and multiphysics solutions are key topics to keep competitiveness and answer to newer industrial needs in plant operations, licensing, and safe operating envelope requirements. The paper presents an overview of the activities performed by Framatome to support the definition of benchmarks exercises proposed in the CAMIVVER Project. Small core configurations subjected to a Reactivity Insertion Accident (RIA) are presented with associated preliminary results. To open the discussions toward the development of Best-Estimate Plus Uncertainties (BEPU) solutions, the URANIE statistical platform was used for sensitivity analysis over different configurations. These preliminary results are also presented.

Transient analysis is a powerful tool for the diagnosis of pressurized pipeline systems, based on the comparison of pressure signals acquired during transients with the results of analytical or numerical models. In this paper the analysis of a transient caused by a pump switch-off is used for the diagnosis of a transmission main managed by Sicilia Acque s.p.a. The measured pressure signals are compared with the results of a frequency domain based numerical model simulating the occurrence of a singularity in the system. The shown results confirm that accidental but rather common functioning conditions of pumping systems, such as pump switch on and off, can be easily and effectively used for their diagnosis.

Global food demand is rising, impelling us to develop strategies for improving the efficiency of photosynthesis. Classical photosynthesis models based on steady-state assumptions are inherently unsuitable for assessing biochemical and stomatal responses to rapid variations in environmental drivers. To identify strategies to increase photosynthetic efficiency, we need models that account for the timing of CO2 assimilation responses to dynamic environmental stimuli. Herein, I present a dynamic process-based photosynthetic model for C3 leaves. The model incorporates both light and dark reactions, coupled with a hydro-mechanical model of stomatal behaviour. The model achieved a stable and realistic rate of light-saturated CO2 assimilation and stomatal conductance. Additionally, it replicated complete typical assimilatory response curves (stepwise change in CO2 and light intensity at different oxygen levels) featuring both short lag times and full photosynthetic acclimation. The model also successfully replicated transient responses to changes in light intensity (light flecks), CO2 concentration, and atmospheric oxygen concentration. This dynamic model is suitable for detailed ecophysiological studies and has potential for superseding the long-dominant steady-state approach to photosynthesis modelling. The model runs as a stand-alone workbook in Microsoft® Excel® and is freely available to download along with a video tutorial.

A technique for calculating transients using the Duhamel integral and discontinuous functions is presented. On specific examples, the procedure for calculating «incorrect» problems with respect to differential equations, compiled according to Kirchhoff laws, and using the Duhamel integral is presented. In this case, the Kirchhoff law and the transition characteristic in the Duhamel integral are written using unitary discontinuous functions for the electrical circuit as a whole (before and after commutation). It is shown that the application of discontinuous functions for describing piecewise continuous input signals and switching in an electric circuit extends the domain of applicability of the Duhamel integral.

The advancement of the design of the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED) beyond the conceptual phase, passes through the analysis of the impact of uncertainties, notably to what concerns safety-related conditions. Compliancy of plant safety to Design Extension Conditions is, according to IAEA and in line with the meaning itself of these beyond-design conditions, usually investigated by best estimates only. Due however to the demonstration nature of ALFRED, it was decided to assess the actual safety performances of this system even in ultimate conditions. To this regard, the emphasis was put on unprotected events like the UTOP (unprotected transient of over-power) and ULOOP (unprotected loss of offsite power, resulting from the combination of a loss of flow and loss of heat sink under unprotected conditions), pinpointed as the most challenging situations sought for the plant. The purpose of the present work, which has been divided in three parts, was then to assess the ultimate ALFRED safety margins against failure of the key core components and systems (Part III). To target this objective, the evaluation of uncertainties coming, on one hand, from nuclear data was performed at first, to retrieve their impact on the reactivity coefficients, thereby on the transient behavior driven by the latter (Part I); then, uncertainties from material properties, fabrication procedures, operation and measurement, and computational tools were propagated to assess their influence on the thermal-hydraulics of the system (Part II). In this work the efforts of Parts I and II are merged together and the effect of uncertainties on safety margins and salient parameters assessed. The retrieved uncertainties are propagated to the expected number of pins experiencing fuel melting during an UTOP and to the clad time-to-failure during an ULOOP. The former has been found to be quite affected by uncertainties, but still under limits not directly posing hazards to the people and the environment, even when extremely conservative assumptions are put forward; the latter shows a milder response to uncertainties, but always guaranteeing more than an order of magnitude of safety margin relative to WENRA recommendations. © 2018 Elsevier Ltd

Sheaths ahead of coronal mass ejections (CMEs) are large heliospheric structures that form with CME expansion and propagation. Turbulent and compressed sheaths contribute to the acceleration of particles in the corona and in interplanetary space, but the relation of their internal structures to particle energization is still relatively little studied. In particular, the role of sheaths in accelerating particles when the shock Mach number is low is a significant open problem. This work seeks to provide new insights on the internal structure of CME sheaths with regard to energetic particle enhancements. A good opportunity to achieve this aim was provided by observations of a sheath made by radially aligned spacecraft at 0.8 and $\sim$ 1 AU (Solar Orbiter, Wind, ACE and BepiColombo) on 19-21 April 2020. The sheath was preceded by a weak shock. Energetic ion enhancements occurred at different locations within the sheath structure at Solar Orbiter and L1. Magnetic fluctuation amplitudes at inertial-range scales increased in the sheath relative to the upstream wind. However, when normalised to the local mean field, fluctuation amplitudes did not increase significantly; magnetic compressibility of fluctuation also did not increase. Various substructures were embedded within the sheath at the different spacecraft, including multiple heliospheric current sheet (HCS) crossings and a small-scale flux rope. At L1, the ion flux enhancement was associated with the HCS crossings, while at Solar Orbiter, the enhancement occurred within the rope. Substructures that are swept from the upstream solar wind and compressed in the sheath can act as particularly effective acceleration sites. A possible acceleration mechanism is betatron acceleration associated with the small-scale flux rope and the warped HCS in the sheath., 14 pages, 12 figures; published in Astronomy & Astrophysics, Solar Orbiter First Results (Cruise Phase) special issue

The study explores the process of dynamic balancing of the impeller of an axial fan VО 06-300 (Ukraine) by two automatic ball balancers.The computer simulation of the dynamics of the fan in the absence and presence of automatic balancers has confirmed the qualitative results of a previously conducted field full-scale experiment. Thus, the presence of automatic balancers reduces the following:– the mean square value of the vibration velocity in the segment from the rotor start to the beginning of automatic balancing,– the vibration velocity values at two resonant peaks when the rotor is running down, and– the peaks of the vibration velocities in the section of the start of automatic balancing (74 times in the 3D modelling; 5.4 times in the field experiment).The computer simulation of the dynamics of the axial fan with the «on» and «off» gravity forces has allowed determining the following:– the effect of gravity on the accuracy of balancing the impeller decreases rapidly with increasing the cruising speed of the impeller,– when increasing the forces of viscous resistance to the motion of the balls, the effect of gravity on the accuracy of the rotor balancing increases;– at low speeds of rotation (15 r/s), the impeller can be balanced not better than by accuracy class G 2.5, but at the rated speed of 25 r/s, it is balanced according to accuracy class G 1.Herewith, the residual vibration velocities that are caused only by gravity decrease with increasing the rotor speed.The residual vibration velocities that are caused only by the eccentricities of the raceways increase directly proportionally to the rotor speed. Therefore, fast-turning rotors need a more precise installation of automatic balancers. It is recommended to reduce the eccentricity of the raceway of the automatic balancer at least 2.5 times in relation to the maximum permissible value.Residual vibration velocities in the automatic balancing mode (up to 3 mm/s) on the test fan are mostly caused by gravity. The probable causes of residual vibration velocities are eccentricities of the raceways of the automatic balancers, standstill of the balls (lack of reaction to small unbalances), etc. Therefore, residual vibration velocities can be reduced at the stages of manufacturing and installing automatic balancers into a fan., Компьютерным 3D моделированием исследован процесс динамической балансировки двумя шаровыми автобалансирами крыльчатки осевого вентилятора. Исследованы режимы разгона, крейсерского движения и выбега вентилятора. Оценена точность балансировки на участке крейсерского движения. Исследовано влияние сил тяжести, вязкого сопротивления движению шаров на точность балансировки крыльчатки. Оценено влияние эксцентриситетов беговых дорожек автобалансиров на точность балансировки, Комп'ютерним 3D моделюванням досліджений процес динамічного балансування кульовими автобалансирами крильчатки осьового вентилятора. Досліджено режими розгону, крейсерського руху і вибігу вентилятора. Оцінена точність балансування на ділянці крейсерського руху. Досліджено вплив сил тяжіння, в’язкого опору руху куль на точність балансування. Оцінений вплив ексцентриситетів бігових доріжок автобалансирів на точність балансування

We derive, evaluate and validate comprehensive analytic modeling of the energy flows in parabolic trough solar thermal power plants. The analytic formulae are straightforward to implement and evaluate, relating to the heat transfer within and from the solar concentrators (including transients, mainly overnight heat losses), and the impact of solar field operation on turbine power and efficiency. Prior numerical simulations used to design solar thermal power systems have either been proprietary or devoid of a fully-reported source code - hence inaccessible or problematic for widespread use. Also, the dependence of these simulations on extensive numerical procedures does not provide a transparent physical picture that grants a clear understanding of how component and system performance vary with the principal operating and input variables - a drawback overcome by the analytic approach presented here. Published experimental measurements of sufficient extent to permit meaningful comparisons between theory and experiment for such solar thermal power plants are exceptionally limited. This narrow data base is used for model validation on both a monthly and an hourly basis. The analytic model is then applied to evaluating a solar power plant now being planned for northeast Brazil, also highlighting the energy-delivery advantages of low-latitude locations. Fil: Salazar, Germán Ariel. Universidade Federal de Pernambuco; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; Argentina Fil: Fraidenraich, Naum. Universidade Federal de Pernambuco; Brasil Fil: Alves de Oliveira, Carlos Antonio. Universidade Federal de Alagoas; Brasil Fil: de Castro Vilela, Olga. Universidade Federal de Pernambuco; Brasil Fil: Hongn, Marcos Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; Argentina Fil: Gordon, Jeffrey M.. Ben Gurion University of the Negev; Israel

The impact of injector life on the spatio-temporal evolution of fuel spray quality was optically investigated using high speed imaging techniques. Both new and used injectors, which had been used in intense operation for up to 90,000 miles, were considered in this investigation. Used injectors are prone to wear, deposit formation, and altered internal nozzle flow. High resolution SEM images clearly portray the presence of carbonaceous deposits both at the injector tip as well as within the holes of used injectors. Investigations revealed that used injectors tend to produce a chaotic hole-to-hole variation at the start of each injection, resulting in an asymmetric early fuel spray penetration pattern in the first 500 μs. Often those sprays that suffered a reduced spray tip penetration rate at the start of injection also showed off-axis transient expansions, and those sprays appeared to be bulky compared to other sprays. Following the early asymmetric spray penetration phase of injection the retarded sprays undergo rapid acceleration with time, and this transformed the early asymmetric spray pattern into a nearly uniform spray pattern from all the orifices in the quasi-steady state regime. The hole-to-hole penetration variations and the resultant asymmetric spray structure at the early start are therefore short lived transient phenomena. However if the radial expansion of the spray is large during the early phase, the radially expanded plume remains almost at the same radial location due to lack of local axial momentum, even after different time instants of spray tip propagation. This appears as a bulge to the spray and can eventually end up as a stationary local pocket of fuel vapor close to the nozzle for the entire duration of injection. This may alter the ignition, flame lift-off and entrainment characteristics of sprays injected from used or deposit rich injectors.

In the field of computational reactor physics, Monte-Carlo methodology is extensively used in the analysis of static problems while the transient behavior of the reactor core is mostly analyzed using deterministic algorithms. However, deterministic algorithms make use of various approximations mainly in the geometric and energetic domain that may induce inaccuracy. Therefore, Monte-Carlo methodology which generally does not require significant approximations seems to be an attractive candidate tool for the analysis of transient phenomena. One of the most important constraints towards this direction is the significant computational cost however since nowadays the available computational resources are continuously increasing, the potential use of the Monte-Carlo methodology in the field of reactor core transient analysis seems feasible. So far, very few attempts to employ Monte-Carlo methodology to transient analysis have been reported. Even more, most of those few attempts make use of several approximations, showing the existence of an “open” research field of great interest. It is obvious that comparing to static Monte-Carlo, a straight-forward physical treatment of a transient problem requires the temporal evolution of the simulated neutrons but this is not adequate. In order to be able to properly analyze transient reactor core phenomena, the proper simulation of delayed neutrons together with other essential extensions and modifications is necessary. This work is actually the first step towards the development of a tool that could serve as a platform for research and development on this interesting but also quite challenging field. More specifically, in this work, a capability for transient neutronic analysis has been introduced in the open-source Monte Carlo code OpenMC. The selected methodology that has been proposed recently by other researchers is inserted in OpenMC following its own features, trying to minimize the necessary modifications and to maximize the advantage by its existing capabilities. The key points of the module which is under development, as well as the results of the analysis of preliminary numerical experiments are presented and discussed. The obtained results are encouraging and very promising in terms of accuracy, giving motivation for further investigation and development. © 2017 Elsevier Ltd 104 103 112 103-112

In this paper, it is tried to compare two methods for determining pure sine and five kinds of power quality disturbances (PQD) such as voltage sag, voltage swell, voltage with harmonics, transients and flicker. These methods are statistical methods and wavelet based effective feature extraction method. Before classifying power quality signals, one of the feature extraction method must be applied. So, these two methods are compared. Firstly, statistical methods are applied to PQD. It is observed that if PQD signal is created at the zero crossing points of the voltage signal, statistical methods give satisfactory result. But occurrence of disturbances at these points is not guaranteed in real systems. It is seen that first method may confuse some PQD according to occurrence place of disturbances. So second method is used for extracting the energy distribution features of PQD constituted in eight different points (00, 450, 900, 1350, 1800, 2250, 2700, 3150). Parseval’s theorem and multi-resolution analysis (MRA) technique of discrete wavelet technique (DWT) are used. It is observed that this method gives satisfactory results for eight different points. © 2017, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ). All rights reserved.

Разработана математическая модель очистного комбайна с встроенной системой подачи и системой автоматического регулирования (САР) с ПИ регулятором. САР позволяет снизить динамические нагрузки на механические части электроприводов очистного комбайна в условиях внезапного изменения крепости угля и возможного стопорения исполнительного органа комбайна. Приводятся результаты исследований переходных процессов нагружения приводов очистного комбайна, возникающих при ступенчатом изменении крепости угля. Показано, что при работе комбайна на слабых углях имеет место снижение быстродействия САР практически в 1,5-2,0раза относительно быстродействия САР при работе комбайна на крепких углях. Предложено для повышения быстродействия САР регулятора тока резания корректировать параметры регулятора в зависимости от сопротивляемости угля резанию. Сделан вывод о необходимости применения интеллектуальных регуляторов., A mathematical model of a shearer-loader with an integrated forward motion drive and an automatic control system (ACS) with a PI controller has been developed. It is shown that ACS allows reducing dynamic loads on the mechanical parts of a shearer-loader electric drives in conditions of a sudden change in coal strength. The results of transient processes arising from a stepwise change in the strength of coal are presented. It is shown that when the combine is working on weak coals, there is a decrease in the ACS speed by almost 1.5-2.0 times relative to the speed of the ACS when the combine is working on strong coals. For promotion the speed of the of the ACS cutting current regulator, it is proposed to adjust the pa-rameters of the regulator depending on the resistance of the coal to cutting. The conclusion is made about the need for the use of intelligent regulators.

SiTian is an ambitious ground-based all-sky optical monitoring project, developed by the Chinese Academy of Sciences. The concept is an integrated network of dozens of 1-m-class telescopes deployed partly in China and partly at various other sites around the world. The main science goals are the detection, identification and monitoring of optical transients (such as gravitational wave events, fast radio bursts, supernovae) on the largely unknown timescales of less than 1 day; SiTian will also provide a treasure trove of data for studies of AGN, quasars, variable stars, planets, asteroids, and microlensing events. To achieve those goals, SiTian will scan at least 10,000 square deg of sky every 30 min, down to a detection limit of $V \approx 21$ mag. The scans will produce simultaneous light-curves in 3 optical bands. In addition, SiTian will include at least three 4-m telescopes specifically allocated for follow-up spectroscopy of the most interesting targets. We plan to complete the installation of 72 telescopes by 2030 and start full scientific operations in 2032., Comment: Accepted by "Annals of the Brazilian Academy of Sciences" as part of the Proceedings for the BRICS Astronomy Workshop (Rio, Brazil, Oct 2019). This revised version includes technical specifications and a map of the planned telescope locations

Корнилов Геннадий Петрович, д-р техн. наук, профессор, заведующий кафедрой «Электроснабжение промышленных предприятий», Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; korn_mgn@mail.ru. Абдулвелеев Ильдар Равильевич, канд. техн. наук, доцент кафедры «Электроснабжение промышленных предприятий», Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; leggyild@mail.ru. Шохин Валерий Владимирович, канд. техн. наук, доцент кафедры «Автоматизированный электропривод и мехатроника», Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; shww@mgn.ru. Храмшин Тимур Рифхатович, канд. техн. наук, доцент кафедры «Электроснабжение промышленных предприятий», Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; timur.hramshin@mail.ru. Николаев Александр Аркадьевич, канд. техн. наук, доцент, заведующий кафедрой «Автоматизированный электропривод и мехатроника», Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; shww@mgn.ru. G.P. Kornilov, korn_mgn@mail.ru, I.R. Abdulveleev, leggyild@mail.ru, V.V. Shokhin, shww@mgn.ru, T.R. Khramshin, timur.hramshin@mail.ru, A.A. Nikolaev, shww@mgn.ru Nosov Magnitogorsk State Technical University, Magnitogorsk, Russian Federation Объектом исследования является система взаимосвязанных электроприводов технологической зоны агрегата непрерывного горячего цинкования цеха покрытий ПАО «Магнитогорский металлургический комбинат» (ПАО «ММК»), в частности механическая часть с упругими элементами и системы управления электроприводами. Целями работы являются: исследование существующих рабочих режимов электроприводов основных механизмов технологической и выходной зон агрегата цинкования, выявление способов улучшения работы системы взаимосвязанных электроприводов в статических и динамических режимах, разработка усовершенствованной системы управления, обеспечивающей улучшенные динамические показатели при косвенном регулировании натяжения полосы. Предлагается новая система управления электроприводами технологической зоны с корректирующей обратной связью по скорости. Динамические характеристики традиционной и новой систем исследовались на математической модели электроприводов исследуемого участка агрегата с учетом их взаимосвязи через упругую полосу. Модель учитывает электроприводы: горячая натяжная станция, натяжные станции № 3, 4, 5, 6 и дрессировочная клеть. Каждый электропривод моделируется с учетом механической инерции и системы управления скоростью или моментом. Сравнительный анализ показателей качества регулирования натяжения для указанных систем показал преимущества разработанной системы. Результаты работы могут быть использованы на аналогичных агрегатах непрерывной обработки полосы, в которых присутствуют участки технологической линии со значительной протяженностью полосы между соседними электроприводами. The paper studies a system of interconnected electric drives in the operational area of the continuous hot dip galvanizing unit located in the coating shop at PJSC Magnitogorsk Iron and Steel Works (PJSC MMK). It particularly focuses on the mechanical part with elastic elements and electric drive control systems. The paper aims at studying the existing operating modes of electric drives of the main mechanisms in the operational and output areas of the galvanizing unit; identifying ways to improve the static and dynamic performance of the interconnected electric drives system; developing an improved control system that provides for the better dynamic performance with indirect strip tension control. The authors propose a new control system for the operational area electric drives with corrective speed feedback. The dynamic characteristics of the traditional and the proposed systems were studied using a mathematical model of electric drives of the analyzed section with account to their interconnection via an elastic strip. The model accounts for eight electric drives, i.e., a hot tension station, tension stations no. 3, 4, 5, 6 and a training stand. Each electric drive is modeled with account for mechanical inertia and a (speed or torque) control system. The comparative analysis of tension control quality indicators for these systems proved the advantages of the developed system. The research outcomes can be used for similar units of continuous strip processing, featuring the technological line sections with a significant length of the strip between the adjacent electric drives. Работа выполнена при финансовой поддержке гранта Президента Российской Федерации для молодых ученых – кандидатов наук МК-499.2020.8.

The recent discoveries of gravitational wave events and in one case also its electromagnetic (EM) counterpart allow us to study the Universe in a novel way. The increased sensitivity of the LIGO and Virgo detectors has opened the possibility for regular detections of EM transient events from mergers of stellar remnants. Gravitational wave sources are expected to have sky localisation up to a few hundred square degrees, thus Gaia as an all-sky multi-epoch photometric survey has the potential to be a good tool to search for the EM counterparts. In this paper we study the possibility of detecting EM counterparts to gravitational wave sources using the Gaia Science Alerts system. We develop an extension to current used algorithms to find transients and test its capabilities in discovering candidate transients on a sample of events from the observation periods O1 and O2 of LIGO and Virgo. For the gravitational wave events from the current run O3 we expect that about 16 (25) per cent should fall in sky regions observed by Gaia 7 (10) days after gravitational wave. The new algorithm will provide about 10 candidates per day from the whole sky., Comment: MNRAS accepted, revised version with corrections from the erratum

The BlackGEM array is the latest addition to the La Silla Observatory. In its first phase it consists of three wide-field telescopes that combine a large field-of-view (2.7 square degrees each) with a spatial resolution (0.56"/pix). The main scientific purpose of BlackGEM is to identify optical counterparts to gravitational wave alerts. To enable this it will also perform a full Southern Sky Survey in six optical bands which will be available through the ESO archive