Untersuchung der Schallentstehung und -abstrahlung elektrischer Maschinen für neuartige elektrifizierte Luftfahrtantriebe

Um die Klimaziele, wie sie beispielsweise von der Europäischen Union formuliert wurden, zu erreichen, werden derzeit neuartige Flugzeugkonzepte mit elektrifizierten Flugantrieben untersucht. Teil dieser Antriebssysteme werden elektrische Maschinen sein, die zum Beispiel im motorischen Betrieb den Propulsor antreiben. In elektrischen Maschinen gibt es eine Vielzahl von Schallquellen, die einen Anteil an der Gesamtschallabstrahlung des elektrischen Antriebsstrangs haben werden. Obwohl die Schallleistungspegel der elektrischen Maschine im Vergleich zu anderen Komponenten gering sein können, spielt hier insbesondere die Tonalität eine wichtige Rolle. Gerade bei direkt angetriebenen Propulsoren und damit langsam drehenden Motoren kann der tonale Schall als besonders störend empfunden werden. Darüber hinaus werden für zukünftige elektrifizierte Antriebsstränge in der Luftfahrt sehr hohe Leistungsdichten gefordert. Diese Anforderungen können unter Umständen einer herkömmlichen akustisch-optimierten Auslegung der Maschine entgegenstehen und für erhöhte Lärmpegel sorgen. Um die Schallabstrahlung elektrischer Maschinen im Kontext elektrifizierter Luftfahrtantriebe besser zu verstehen, werden zukünftig verschiedene Motortopologien vergleichbarer Leistung mittels FEM simuliert und der entstehende Schall, hervorgerufen durch die Luftspaltkräfte zwischen Rotor und Stator, ermittelt. Ziel der Arbeiten ist es somit, ein besseres Verständnis der Schallentstehung und -abstrahlung elektrischer Maschinen für neuartige Luftfahrtantriebe zu erlangen, um unter anderem frühzeitig im Entwurfsprozess Einfluss nehmen und gegebenenfalls Lärmminderungsmaßnahmen etablieren zu können

Non-inhibitory levels of oxygen during cultivation increase freeze-drying stress tolerance in Limosilactobacillus reuteri DSM 17938

The physiological effects of oxygen on Limosilactobacillus reuteri DSM 17938 during cultivation and the ensuing properties of the freeze-dried probiotic product was investigated. On-line flow cytometry and k-means clustering gating was used to follow growth and viability in real time during cultivation. The bacterium tolerated aeration at 500mL/min, with a growth rate of 0.74 +/- 0.13h(-1) which demonstrated that low levels of oxygen did not influence the growth kinetics of the bacterium. Modulation of the redox metabolism was, however, seen already at non-inhibitory oxygen levels by 1.5-fold higher production of acetate and 1.5-fold lower ethanol production. A significantly higher survival rate in the freeze-dried product was observed for cells cultivated in presence of oxygen compared to absence of oxygen (61.8%+/- 2.4% vs. 11.5%+/- 4.3%), coinciding with a higher degree of unsaturated fatty acids (UFA:SFA ratio of 10 for air sparged vs. 3.59 for N-2 sparged conditions.). Oxygen also resulted in improved bile tolerance and boosted 5 ' nucleotidase activity (370U/L vs. 240U/L in N-2 sparged conditions) but lower tolerance to acidic conditions compared bacteria grown under complete anaerobic conditions which survived up to 90min of exposure at pH 2. Overall, our results indicate the controlled supply of oxygen during production may be used as means for probiotic activity optimization of L. reuteri DSM 17938

Comparative assessment of the bacterial communities associated with Anopheles darlingi immature stages and their breeding sites in the Brazilian Amazon

Background The neotropical anopheline mosquito Anopheles darlingi is a major malaria vector in the Americas. Studies on mosquito-associated microbiota have shown that symbiotic bacteria play a major role in host biology. Mosquitoes acquire and transmit microorganisms over their life cycle. Specifically, the microbiota of immature forms is largely acquired from their aquatic environment. Therefore, our study aimed to describe the microbial communities associated with An. darlingi immature forms and their breeding sites in the Coari municipality, Brazilian Amazon.Methods Larvae, pupae, and breeding water were collected in two different geographical locations. Samples were submitted for DNA extraction and high-throughput 16S rRNA gene sequencing was conducted. Microbial ecology analyses were performed to explore and compare the bacterial profiles of An. darlingi and their aquatic habitats.Results We found lower richness and diversity in An. darlingi microbiota than in water samples, which suggests that larvae are colonized by a subset of the bacterial community present in their breeding sites. Moreover, the bacterial community composition of the immature mosquitoes and their breeding water differed according to their collection sites, i.e., the microbiota associated with An. darlingi reflected that in the aquatic habitats where they developed. The three most abundant bacterial classes across the An. darlingi samples were Betaproteobacteria, Clostridia, and Gammaproteobacteria, while across the water samples they were Gammaproteobacteria, Bacilli, and Alphaproteobacteria.Conclusions Our findings reinforce the current evidence that the environment strongly shapes the composition and diversity of mosquito microbiota. A better understanding of mosquito-microbe interactions will contribute to identifying microbial candidates impacting host fitness and disease transmission

Shared heritability and functional enrichment across six solid cancers

Correction: Nature Communications 10 (2019): art. 4386 DOI: 10.1038/s41467-019-12095-8Quantifying the genetic correlation between cancers can provide important insights into the mechanisms driving cancer etiology. Using genome-wide association study summary statistics across six cancer types based on a total of 296,215 cases and 301,319 controls of European ancestry, here we estimate the pair-wise genetic correlations between breast, colorectal, head/neck, lung, ovary and prostate cancer, and between cancers and 38 other diseases. We observed statistically significant genetic correlations between lung and head/neck cancer (r(g) = 0.57, p = 4.6 x 10(-8)), breast and ovarian cancer (r(g) = 0.24, p = 7 x 10(-5)), breast and lung cancer (r(g) = 0.18, p = 1.5 x 10(-6)) and breast and colorectal cancer (r(g) = 0.15, p = 1.1 x 10(-4)). We also found that multiple cancers are genetically correlated with non-cancer traits including smoking, psychiatric diseases and metabolic characteristics. Functional enrichment analysis revealed a significant excess contribution of conserved and regulatory regions to cancer heritability. Our comprehensive analysis of cross-cancer heritability suggests that solid tumors arising across tissues share in part a common germline genetic basis.Peer reviewe

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

Detached Eddy Simulation der Strömung und des Schallfelds eines subsonischen Freistrahls bei moderater Reynolds-Zahl

Strahllärm hat beim Start eines Flugzeuges einen wesentlichen Anteil am entstehenden Fluglärm. Es ist daher nach wie vor von großem Interesse, die zugrunde liegenden Mechanismen der Schallentstehung zu untersuchen und zu verstehen. Dazu können skalenauflösende numerische Simulationen unter Verwendung von hybriden LES-Verfahren durchgeführt werden. Zu diesen Verfahren zählt die sogenannte Detached Eddy Simulation, bei der das Turbulenzmodell in der Nähe fester Wände im RANS-Modus und im verbleibenden, meist abgelöstem Bereich, im LES-Modus läuft. Die so, im akustischen Nahfeld des Strahls, berechneten Strömungsfelder werden anschließend mit einem Ffowcs-Williams-Hawking Verfahren ins Fernfeld projiziert, um dort die akustischen Druckschwankungen zu bestimmen. Statistische Analysen der Simulationsergebnisse geben darüber hinaus einen Einblick in die Aerodynamik des turbulenten Strahls und tragen somit zum Verständnis der Effekte bei. In der hier behandelten Konfiguration strömt Luft mit einer (aerodynamischen) Mach-Zahl von 0,9 aus einer Düse mit einem Durchmesser von 1 Zoll. Durch ein, an der Innenseite der Wand, befestigtes Zackenband wird die Grenzschicht in der Düse und die daraus entstehende freie Scherschicht des Strahls positiv beeinflusst, was zu einer Lärmreduzierung im Fernfeld führt. Dieser bereits in Experimenten nachgewiesene Effekt soll durch die numerischen Simulationen bestätigt werden

Multiphysics Numerical Simulation of Electric Motor Noise for Electrified Aero Engines

In order to contribute to the ongoing efforts against climate change, the European Commission has published a document called Flightpath 2050, which sets out objectives and targets for the aviation sector to reduce the environmental impact of aircraft and their associated and necessary infrastructure. These targets are aimed at reducing water vapour and contrails, ozone and soot, NOx and CO2 as well as noise. In this context, alternative propulsion systems for commercial aircraft are being considered. These new propulsion systems will have electric machines either to drive the propulsor directly or to assist the gas turbine in certain flight phases. At present, different types of architectures of electrified aero-engines and propulsion systems are being investigated by industry and research groups around the world, and there are numerous topologies of electrical machines that may be applicable and suitable for these systems. New motor and generator technologies are also emerging at regular intervals. Although noise from electrical machines has been studied for some time in the automotive and power generation sectors, data, methods and models for electric motor noise for future aircraft propulsion systems are scarce. The high power and speed requirements of electrical machines for future aircraft will result in significant sources of tonal noise. Testbed measurements will help to quantify the resulting far-field noise levels and their directivity. This will pave the way for the establishment of analytical and numerical prediction methods. Experimentally verified numerical simulation methods will provide a better understanding of the physical noise generation mechanisms and support the development of noise mitigation techniques. In this paper, a multiphysics numerical simulation of electromagnetic forces coupled with structural modal analysis is performed to assess the vibration and radiated noise of an electric machine suitable for an aircraft propulsion system. This work includes the calculation of the radial electromagnetic force density in the air gap for machines under different load conditions and the data processing necessary to obtain the temporal and spatial distribution of the stress. Based on these results, subsequent simulations will provide the frequencies and vibration modes of the structure, as well as the vibration velocity and displacement of the casing surface, which will ultimately allow the prediction of the resulting far-field noise levels

Investigations on Pulsating Turbine Flow: Determination of turbine power und the influence of pulsating exhaustgas admission

During recent years a research project concerning the influence of pulsating turbine admission on the flow and efficiency properties of the turbocharger turbine has been carried out at the institute of internal combustion engines at the technical university of Berlin. Qualifying the differences between steady state and pulsating admission was the major aspect of the project. During the project experimental investigations as well as multiple one dimensional simulations and three dimensional CFD simulations have been carried out. Those investigation allowed a detailed view into the turbine during pulse admission and information about the course of the torque at the turbine shaft could be gained. Furthermore a recommendation for the application of pulse admissioned tubines in 1-D engine process simulation has been derived

Noise prediction for the HBK2/Toshiba Rig using the DLR tool HEIDI

The High Pressure Combustion Chamber Test Rig 2 (HBK 2) is a test bed situated at the DLR site in Cologne that is capable of a wide range of operating conditions. It delivers different kind of gas compositions at high pressures and temperatures in order to test and analyze a variety of combustion setups. The flow exits through a nozzle into ambient air and leaves the test bed via a duct to the outside. Due to the high flow velocities at the end of the nozzle jet noise with high amplitudes will occur. The department of Engine Acoustics has been assigned to give an estimate of the resulting noise levels

Hot-wire measurements in a Direct Driven high speed Turbo Fan (DDTF) rig

The German Aerospace Center (DLR) has measured and analyzed the unsteady flow field of a representative Direct Driven Turbo Fan (DDTF) stage by using hot-wire anemometry. Measurements were conducted together with the partner Rolls-Royce at the fan test bed of AneCom AeroTest. The averaged mean vectors as well as the fluctuating components of the velocity in the wake of each individual rotor blade were determined and the local turbulence distribution was calculated for various axial and radial positions downstream of the rotor. The calculated local turbulence distribution of the flow downstream of the rotating blades shows an increase of the turbulence intensity from 4.5% up to 12 % in the wake depending on the operating point. The variation of the axial position downstream of the rotor describes the mixing process of the rotor blade wakes. With increasing distance from the trailing edge of the rotor the turbulence intensities levels are getting more equalized