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Vibration Optimized Magnetic Rotor Suspension with Individual Permanent Magnets
Get PDFIn this paper, an investigation of a vibration-optimized arrangement of individual permanent magnets for radialmagnetic suspension of a machine rotor is presented. In contrast to previous work. the investigationconsiders spacing constraints between individual magnets that may appear in a 3D printed machine design. It is shownby means of a finite element (FE) simulation that the magnitude of the suspension force fluctuates depending on the rotorrotation angle and may hence cause vibrations during machine operation. It is investigated how these magnitudefluctuations depend on the concrete configuration of the individual magnets and which configurations lead to a minimumof fluctuations and hence a minimum of suspension related machine vibrations
Source Localisation Measurements with Microphone Arrays on Turbofan and Open Rotor Engines
Get PDFPresentation of the microphone array measurements planned in the framework on the COMPANION project and the method for analysing the data with SODIX for the hybrid electric UHBR turbofan and open rotor engines at model scale in wind tunnels and in full scale flight-tests
Real-time air-traffic warning during satellite re-entries: Challenges and developments
No full textOver time, new market trends are shaped by advances in technological development. The space sector is no exception to this evolution, with launches across all mass and type classes reaching record levels in recent years. In terms of re-entries, this translates into a rapid increase in the number of re-entering objects. Between 10 % and 40 % of the re-entering mass is expected to survive, posing a potential hazard to aircraft, ships and ground populations. Alongside to the uncertainty on the surviving mass, the on-ground risk assessment is still strongly affected by the uncertainties in predicting the re-entry point, which is estimated around 20 % of the remaining lifetime for an uncontrolled re-entry from a circular orbit. Despite these challenges, the theory for the on-ground risk assessment is in a certain extent harmonised within the international context of space agencies. In contrast, the assessment of the risk that re-entering objects pose to air and sea traffic is still a major point of discussion today, with methodologies that can vary widely from one country/agency/entity to another. This paper discusses key challenges that are currently hindering the implementation of real-time air traffic warnings during Earth's atmospheric re-entries, ranging from technical gaps to the lack of clear metrics or a centralised coordination point, and outlines recent developments aimed at mitigating these issues. The first section of this work provides an overview of relevant historical events and comments the international response to the increased risk, while the second section discuss the challenges for the practical implementation of a real-time risk assessment for air traffic during the re-entry of space objects, and propose near-term steps for a overcoming them
Estimation of Calving Law Parameters from Satellite Data
Get PDFCapturing the calving front motion is critical for simulations of ice shelves and tidewater glaciers. Multiple physical processes, including sliding, water pressure and failure need to be understood to accurately model the front. Calving is particularly challenging due to its discontinuous nature and modellers require more tools to examine it. A common technique for capturing the front in ice simulations is the Level-set method. The front is represented implicitly by the zero isoline of a function. The movement of the front is described by a Hamilton-Jacobi PDE where the velocity of the front includes two components: the horizontal velocity of the ice sheet and the ablation rate, i.e., the sum of melting and calving rates. We are developing scalable simulation code to solve the Level-set problem and to estimate parameters of calving laws from satellite images using numerical optimization. The method is adaptable to different types of calving laws as well as other interface capturing problems and handles temporal sparsity of observations and coupling with an ice sheet model. The code is sufficiently scalable for large scale, high resolution models of continental ice sheets
Probing Surface Degradation Pathways of Charged Nickel-Oxide Cathode Materials Using Machine-Learning Interatomic Potentials
No full textWhile nickel-based layered oxide cathodes offer promising energy and power densities in lithium-ion batteries, they suffer from instability when fully delithiated upon charge. Ex situ studies often report a structural degradation of the charged cathode materials, but the precise mechanism is still poorly understood on the atomic scale. In this work, we combine high-level ab initio calculations with molecular dynamics using machine-learning interatomic potentials to study structural degradation of fully delithiated LiNiO2 surfaces at the top of charge. We find a previously unreported, stable reconstruction of the (012) facet with more facile oxygen loss compared to the pristine surfaces. The oxygen vacancy formation energy closely corresponds to the experimental decomposition temperatures of charged cathodes. Furthermore, we use molecular dynamics simulations to sample Ni ion migration into alkali-layer sites that is a kinetically plausible initiation step for surface degradation toward thermodynamically stable products
Asymmetric electronic band alignment and potentially enhanced thermoelectric properties in phase-separated Mg2X (X = Si,Ge,Sn) alloys
Get PDFThe Mg2X (X = Si, Ge, Sn) based alloy is an eco-friendly thermoelectric material for mid-temperature applications. The Mg2Si1−xSnx and Mg2Ge1−xSnx alloys can be phase-separated into Si(Ge)- and Sn-rich phases during material synthesis, leading to a nanocomposite with locally varying electronic band structures. First-principles calculations reveal that the valence band offset is eight-times larger than the conduction band offset at the interface between Si- and Sn-rich phases for x = 0.6, showing type I and asymmetric band alignment (0.092 vs 0.013 eV). Using the Boltzmann transport theory and thermionic emission calculations, we show that the large valence band energy discontinuity could allow for energy filtering effects to take place that can potentially increase the power factor substantially in the p-type material system if designed appropriately
Aircraft Dent Detection Utilizing Specular Reflections and Deep Learning
Get PDFThe aviation industry requires frequent and thorough visual inspections to find and evaluate defects, which are expensive and time-consuming. Automating parts of the inspection process using robots and deep learning has the potential to improve speed and performance. Dents are the most difficult type of defect to detect, since they usually lack distinguishing colors, and can only be seen via shadows or reflections. To make dent detection easier and more reliable for deep learning models, a capturing setup utilizing specular reflections is tested. This necessitates the creation of a new dataset of aircraft surface images, where dents are made visible with the help of specular reflections. A new annotation method that makes use of an optical tracking system to automatically create annotations was developed to create the dataset. Two different models were trained on variations of the dataset and tested to determine their ability to detect dents in specular reflection images, and their viability for use in a robotic inspection scenario. This thesis shows that both RT-DETR and YOLOv12 have excellent dent detection performance on the new dataset, are fast and accurate when processing video, and can be suitably integrated into a robotic inspection setup
State of the art review: Investigation of various modeling strategies for chemicals in the field of synthetic resins
Get PDFDue to the large number of chemicals and the variety in their production pathways, there can be considerable gaps and associated uncertainties while conducting Life Cycle Assessments (LCA), especially during the phase of the life cycle inventory (LCI). In this regard, commercial databases and previous modelling approaches have focused on estimating values and proxies in the absence of specific industrial or confidential data. These methodologies are continuously developed and adapted in multiple approaches. However, a challenge that should not be neglected is the need for detailed and case-specific literature research and comprehensive knowledge of the chemical-technical field, which can lead to misunderstandings, errors and the exclusion of important information in the modelling phase, especially for practitioners unfamiliar with the subject. Despite various methodologies for modelling the LCI, especially for resin systems and their raw materials, there is no established and uniform framework for simplified modelling. In this research we want to show which methodologies are used to create these customised LCIs and what their similarities and differences are. It can be shown how conventional databases, like Ecoinvent or Cm.chemicals, and recent modelling approaches deal with data gaps. In addition to the common basis for these databases, it will be examined how new data sets can be developed independently with the help of databases in combination with current modelling strategies in order to create a consistent yet comprehensive LCI. The results help to provide some insight into the overview and comparison of existing methodologies and draw attention to the associated uncertainties. This lays the foundation of providing a future framework to pursue a suitable and uniform modelling strategy in accordance with the existing databases. The overview carried out can support non-specialist LCA practitioners in particular to apply a suitable methodology when creating a detailed and holistic LCA for resin systems
Ionospheric indices for characterizing ionospheric perturbations and warning users of trans-ionospheric radio systems
Get PDFSevere ionospheric plasma perturbations can seriously affect the accuracy, continuity, availability, and integrity of space-based radio systems such as Global Navigation Satellite Systems (GNSS) and remote sensing radars. Computing well-defined ionospheric indices can help to characterize the type and degree of ionospheric perturbations and to improve our understanding of the underlying physics of these perturbations. Additionally, indices can warn users concerning the ionospheric impact on the performance of radio systems like GNSS. Users are interested in receiving near real-time information about the type, intensity, and dynamics of ionospheric perturbations over time and space. This talk will address these topics based on recent DLR developments on ionospheric indices, such as the Gradient Ionosphere indeX (GIX) and the Sudden Ionosphere Disturbance indeX (SIDX). The capabilities, strengths, and limitations of these indices will be reviewed by considering sample studies under various geophysical conditions. The talk will underline the practical value of continuously monitoring and computing these indices at the national Ionospheric Monitoring and Prediction Center (IMPC) at DLR. This information service predicts the occurrence of severe perturbations and warns customers, particularly those in safety-critical applications such as aviation or automated GNSS positioning and navigation devices. To enable customers to permanently estimate the risk level of violating performance criteria required in the specific radio system they use, we suggest index-based perturbation scales of ionospheric electron density
Investigation of Diffusion Mechanisms in ABO3-δ Perovskites and related Ordered Oxygen Vacancy Structures with Nudged Elastic Band Calculations
No full textPerovskite oxides are of interest as a redox material for thermochemical cycles, since their ABO3 stoichiometry allows to tailor them efficiently to the needs of various applications. Due to partial reduction, which reaches significant off-stoichiometries between 0 < δ < 0.5, perovskites promise good process efficiencies. Tailoring of perovskites requires knowledge of their thermodynamic and kinetic properties, however these are assumed to change with increasing degree of reduction. During the initial stages of reduction, isolated oxygen vacancies (VO) are introduced into the perovskite lattice. With increasing δ, perovskites undergo a reversible phase transition, since the VO are starting to interact and transform the perovskite into an ordered oxygen vacancy (OOV) structure. This Thesis investigates the thermodynamics of the perovskite CaMnO3-δ and the oxygen deficient variant CaMnO2.5+δ, using first-principle density functional theory (DFT) calculations. Additionally, oxygen diffusion kinetics are investigated, using a combination of DFT and the Nudged Elastic Band (NEB) method. At the initial stage of reduction with δ ≈ 0, formation energy and diffusion of isolated VO within the defect perovskite CaMnO3-δ are investigated. For this case, an oxygen vacancy formation energy of EVO,δ≈0 = 1.94 eV (187 kJ/mol) is found. The diffusion in defect perovskite is found to be approximately isotropic, due to similar barriers Em ≈ 0.7 eV (68 kJ/mol) in all three dimensions. At the final state of reduction with δ ≈ 0.5, different variants of OOV-structures are compared with respect to their configurational energy, to find preferable structures for CaMnO2.5. As a result, two promising structures are found: the structure being known as Brownmillerite, and a structure, which has been experimentally determined for CaMnO2.5. These OOV-structures are employed to investigate the formation energy and diffusion of an oxygen atom on an interstitial lattice site within oxygen deficient CaMnO2.5+δ. As a result, the diffusion mechanics and barriers in OOV-structures do not only differ from those of VO diffusion in perovskite, but also vary among the different OOV-structures, themselves. Finally, both thermodynamic properties and oxygen diffusion mechanisms are compared for the two limiting cases δ ≈ 0 and δ ≈ 0.5, with the aim to learn about the problems and chances, which arise by the similarities and differences between both cases. This knowledge is of high importance for the purposeful tailoring of perovskites, to employ them as suitable redox materials for thermochemical cycles