Effiziente Modellierung von Windenergieanlagen mit doppelt gespeister Asynchronmaschine und Vollumrichter für Untersuchungen der Frequenzstabilität

The contribution of wind turbines (WTs) to enhance the frequency stability of power systems is traditionally analyzed using commonly applied root mean square (RMS) models. RMS WT models require smaller simulation time steps compared to conventional active devices (i.e., synchronous generators and dynamic loads) due to the comparatively smaller time constants of the converter controllers. Such small time steps become relevant in simulations of large-scale power systems with a high level of WT penetration and lead to high computational time and effort. This paper presents simplified simulation models of a doubly-fed induction generator-based WT and a full-scale converter-based WT, which enable higher simulation time steps due to the negligence of very small time constants with no relevant effects in the time frame of interest of frequency stability analysis. The models are derived from detailed RMS WT models based on fundamental machine and converter equations. In order to verify the validity of the underlying simplifications, the simplified models are compared to the detailed RMS models with a focus on their general behavior in case of step responses and their frequency responses in the event of a frequency drop in a 220 kV test system. For this purpose, both the detailed RMS WT models as well as the simplified WT models are extended with a droop-based fast frequency response controller and implemented in a MATLAB-based RMS simulation tool. The results of the case studies show feasible and comparable general behavior of the WT models as well as plausible frequency responses.Der Beitrag von Windenergieanlagen (WEA) zur Erhöhung der Frequenzstabilität wird klassischerweise mit quasistationären Modellen untersucht. Die Verwendung quasistationärer Modelle von WEA erfordert, aufgrund der im Vergleich zu konventionellen aktiven Betriebsmitteln (wie Synchronmaschinen oder dynamischen Lasten) kleineren Zeitkonstanten der Umrichterregelung, kleinere Zeitschritte in der Simulation. Diese kleinen Zeitkonstanten werden relevant bei der Simulation ausgedehnter Elektroenergiesysteme mit hohem Anteil von WEA und führen zu hohen Rechenzeiten. In dieser Veröffentlichung werden vereinfachte Modelle für WEA mit doppelt gespeister Asynchronmaschine bzw. mit Vollumrichter vorgestellt. Durch die Vernachlässigung kleiner Zeitkonstanten ohne größere Auswirkungen im Zeitbereich der Frequenzstabilität können die Zeitschritte der Simulation deutlich erhöht werden. Die Modelle werden aus detaillierten quasistationären Modellen abgeleitet, die auf den grundlegenden Gleichungen der Maschinen und Umrichter basieren. Um die Gültigkeit der getroffenen Vereinfachungen zu bestätigen, werden die vereinfachten mit den detaillierten quasistationären Modellen verglichen. Der Fokus liegt dabei auf der Sprung- und Frequenzantwort im Falle eines Frequenzeinbruchs in einem 220-kV-Testsystem. Für die Untersuchungen werden die vereinfachten und die detaillierten Modelle um einen auf einer Statik basierenden Fast Frequency Response-Regler ergänzt und in einem quasistationären Simulationstool in MATLAB implementiert. Die Ergebnisse der Fallstudien zeigen plausible und vergleichbare Verhalten der Modelle der WEA sowie plausible Frequenzverläufe

Premios Isabel Zendal de Promoción do Pensamento Crítico en Educación Secundaria e Bacharelato. II Edición

A segunda edición dos Premios Isabel Zendal preséntase como unha actividade de extensión universitaria da Universidade da Coruña, por medio da Unidade de Divulgación Científica e Cultural e en colaboración co Círculo Escéptico. A súa finalidade é promover o pensamento crítico e a cultura científica entre a xuventude, vítima en moitas ocasións da difusión e divulgación de informacións e crenzas falsas. O premio está dirixido ao alumnado escolarizado en centros educativos españois, desde o primeiro curso da educación secundaria obrigatoria (ESO) ata o segundo curso de bacharelato, de modo que consta de dúas categorías de participación: unha para o alumnado de 1.º a 3.º curso da ESO e FP básica; e outra para o alumnado de 4.º da ESO a 2.º de bacharelato, máis os ciclos formativos de grao medio. A participación no concurso realízase a través dun xénero literario —que pode ser un artigo xornalístico— a exposición divulgativa dun experimento desenvolvido polo alumnado, o conto ou o relato curto. Valórase que os traballos integren os valores do pensamento escéptico e científico, a difusión do coñecemento, a ciencia e os seus métodos e a refutación das pseudociencias, así como a loita contra a difusión de enganos e as novas falsas. Neste documento recóllense os traballos premiados nesta segunda edición dos Premios Isabel Zendal, convocada en marzo de 2020 e cuxa resolución tivo lugar en xullo do mesmo ano. Xurado: Francisco Armesto Ramón, Marisa Castiñeira García, Manuel Francisco Herrador Barrios, Susana Ladra González, Xoán Luís López Viñas e M.ª Cristina Naya Riveiro

Effectiveness of Fosfomycin for the Treatment of Multidrug-Resistant Escherichia coli Bacteremic Urinary Tract Infections

IMPORTANCE The consumption of broad-spectrum drugs has increased as a consequence of the spread of multidrug-resistant (MDR) Escherichia coli. Finding alternatives for these infections is critical, for which some neglected drugs may be an option. OBJECTIVE To determine whether fosfomycin is noninferior to ceftriaxone or meropenem in the targeted treatment of bacteremic urinary tract infections (bUTIs) due to MDR E coli. DESIGN, SETTING, AND PARTICIPANTS This multicenter, randomized, pragmatic, open clinical trial was conducted at 22 Spanish hospitals from June 2014 to December 2018. Eligible participants were adult patients with bacteremic urinary tract infections due to MDR E coli; 161 of 1578 screened patients were randomized and followed up for 60 days. Data were analyzed in May 2021. INTERVENTIONS Patients were randomized 1 to 1 to receive intravenous fosfomycin disodium at 4 g every 6 hours (70 participants) or a comparator (ceftriaxone or meropenem if resistant; 73 participants) with the option to switch to oral fosfomycin trometamol for the fosfomycin group or an active oral drug or pa renteral ertapenem for the comparator group after 4 days. MAIN OUTCOMES AND MEASURES The primary outcome was clinical and microbiological cure (CMC) 5 to 7 days after finalization of treatment; a noninferiority margin of 7% was considered. RESULTS Among 143 patients in the modified intention-to-treat population (median [IQR] age, 72 [62-81] years; 73 [51.0%] women), 48 of 70 patients (68.6%) treated with fosfomycin and 57 of 73 patients (78.1%) treated with comparators reached CMC (risk difference, -9.4 percentage points; 1-sided 95% CI, -21.5 to infinity percentage points; P = .10). While clinical or microbiological failure occurred among 10 patients (14.3%) treated with fosfomycin and 14 patients (19.7%) treated with comparators (risk difference, -5.4 percentage points; 1-sided 95% CI. -infinity to 4.9; percentage points; P = .19), an increased rate of adverse event-related discontinuations occurred with fosfomycin vs comparators (6 discontinuations [8.5%] vs 0 discontinuations; P = .006). In an exploratory analysis among a subset of 38 patients who underwent rectal colonization studies, patients treated with fosfomycin acquired a new ceftriaxone-resistant or meropenem-resistant gram-negative bacteria at a decreased rate compared with patients treated with comparators (0 of 21 patients vs 4 of 17 patients [23.5%]; 1-sided P = .01). CONCLUSIONS AND RELEVANCE This study found that fosfomycin did not demonstrate noninferiority to comparators as targeted treatment of bUTI from MDR E coli; this was due to an increased rate of adverse event-related discontinuations. This finding suggests that fosfomycin may be considered for selected patients with these infections

EUREC⁴A

The science guiding the EUREC⁴A campaign and its measurements is presented. EUREC⁴A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC⁴A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC⁴A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC⁴A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement

EUREC⁴A

The science guiding the EUREC⁴A campaign and its measurements is presented. EUREC⁴A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC⁴A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC⁴A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC⁴A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement

A Diffusivity Study of (Sc₂O₃)_0.1(CeO₂)_0.01(ZrO₂)_0.89 between 1100 and 1500 K at Zero Pressure with Molecular Dynamics

Zirconium dioxide (ZrO₂) codoped with 10 mol % scandium­(III) oxide Sc₂O₃ and 1 mol % cerium dioxide CeO₂ (10Sc1CeSZ) is a relevant electrolyte material for high temperature fuel or electrolysis cells, due to its high ionic conductivity and its stability in the cubic phase in comparison to other metal oxides. Despite the many experimental studies for 10Sc1CeSZ, there are to our knowledge no computational studies of this material. In this paper, we calculate the diffusivities and ionic conductivity of 10Sc1CeSZ using classical molecular dynamics for different temperatures and the density at zero pressure in the canonical ensemble. Our results for the ionic conductivity are comparable with experimental data for temperatures equal to or above 1200 K. This may hopefully also be the case for the Brownian diffusion coefficient and the tracer diffusion coefficient calculated in this work, for which no literature values are available. The values given in this paper can be used in future studies describing transport phenomena in fuel or electrolysis cells with 10Sc1CeSZ electrolytes

A IMPORTÂNCIA DA APRENDIZAGEM E DO TREINAMENTO PARA A REDUÇÃO DOS ACIDENTES DE TRABALHO

A aprendizagem que se dá através de treinamentos técnicos e comportamentais visa possibilitar posturas e práticas seguras e o desenvolvimento de uma consciência de segurança, e redução dos casos de acidentes e doenças ocupacionais. E, através do desenvolvimento de habilidades para a realização das atividades de maneira mais segura, aumenta-se a percepção dos trabalhadores sobre os riscos existentes no ambiente de trabalho, sendo uma das consequências positivas para a instituição e para o governo, a redução do ônus trabalhista e previdenciário, decorrentes dos acidentes de trabalho. Em muitas organizações ocorrem o desenvolvimento de programas de capacitação periódicos, através da interação entre os departamentos de recursos humanos, segurança, saúde e meio ambiente. Existem mais abrangentes do que a própria legislação, específicos aos perigos e riscos das atividades, o que acontece é basicamente o atendimento a questões legais, quando ocorre, sem se preocupar com a qualidade destes treinamentos, adequação do conteúdo e a proficiência dos profissionais que ministram o treinamento