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The L-band Digital Aeronautical Communications System (LDACS) is a cellular-based broadband, secure digital aeronautical communications system designed to enhance the safety and efficiency of air traffic management (ATM) through the facilitation of innovative ATM paradigms, such as 4D trajectory-based operations (TBO). LDACS is in its final stages of standardization by the International Civil Aviation Organization (ICAO) and the European Organisation for Civil Aviation Equipment (EUROCAE). Furthermore, it has been introduced to not only the aviation industry but also the Internet community in the form of an informational Request For Comments (RFC). Rapidly creating prototypes of an international communications standard by multiple organizations is crucial to the effective deployment of that standard. This approach enables validation and interoperability testing across various countries’ prototypes. Therefore, first, we create an LDACS prototype through a software/hardware co-design strategy by Software Defined Radio (SDR) and High-Level Synthesis (HLS). This approach expedites and economically streamlines the development process. Second, we show the alignment of our prototype with the LDACS specification through preliminary and cell entry tests. Third, we demonstrate the efficacy of LDACS’ Quality of Service (QoS) and security features via end-to-end IPv6 connectivity and security tests. Finally, the soundness and clarity of the LDACS specification is evidenced via interoperability tests between our prototype and a European counterpart.

Abstract Background Following a first wave in spring and gradual easing of lockdown, Luxembourg experienced an early second epidemic wave of SARS-CoV-2 before the start of summer school holidays on 15th July. This provided the opportunity to investigate the role of school-age children and school settings for transmission. Methods We compared the incidence of SARS-CoV-2 in school-age children, teachers and the general working population in Luxembourg during two epidemic waves: a spring wave from March–April 2020 corresponding to general lockdown with schools being closed and May–July 2020 corresponding to schools being open. We assessed the number of secondary transmissions occurring in schools between May and July 2020 using routine contact tracing data. Results During the first wave in March–April 2020 when schools were closed, the incidence in pupils peaked at 28 per 100,000, while during the second wave in May–July 2020 when schools were open, incidence peaked 100 per 100,000. While incidence of SARS-CoV-2 was higher in adults than in children during the first spring wave, no significant difference was observed during the second wave in early summer. Between May and July 2020, we identified a total of 390 and 34 confirmed COVID-19 cases among 90,150 school-age children and 11,667 teachers, respectively. We further estimate that 179 primary cases caused 49 secondary cases in schools. While some small clusters of mainly student-to-student transmission within the same class were identified, we did not observe any large outbreaks with multiple generations of infection. Conclusions Transmission of SARS-CoV-2 within Luxembourg schools was limited during an early summer epidemic wave in 2020. Precautionary measures including physical distancing as well as easy access to testing, systematic contact tracing appears to have been successful in mitigating transmission within educational settings.

In a previous paper, it was determined that coolant fluids can have a significant influence on the acoustic emission of an electric motor. There is no appliance that can investigate and compare the transfer path analysis of isolated fluids. For this case, a new fixture is introduced and its suitability is evaluated. Furthermore, the appliance is used to measure and compare different media and their frequency response functions. The results indicate that the fixture and its repeatability are suitable to measure and compare fluids and media. A comparison of different media shows how the air medium has the lowest amplitudes for the transfer path analysis, in relation to incompressible fluids. Furthermore, differences in the transfer path analysis between both considered gearbox oils are marginal. While the utilization of air as a coolant medium is not always possible, due to thermal issues, the presented fixture can help find an acoustically suitable coolant medium for future applications in electric motors. Additionally, it is possible to investigate the influence of temperature and pressure conditions on the transfer path analysis of fluids.

In this paper, the frequency response functions of rubber o-rings are investigated. A growing trend is the application of electric motors in vehicle powertrains. Electric motors exhibit a different kind of structural dynamic excitation, compared to conventional internal combustion engines. Especially the excitation frequency is multiple times higher, as in combustion engines. This increased excitation frequency is a novel requirement on materials and their modelling in simulations. For this case, a novel fixture is introduced, which constrains the rubber o-ring components in their designated conditions and which allows to perform a Transfer-Path-Analysis up to a frequency of 6.5 kHz. The evaluation of the results shows a high coherence throughout the considered frequency range, while using a high-frequency miniature shaker. The structural resonances are clearly visible and the signal noise is low. This proves the suitability of the presented fixture, in combination with the high-frequency miniature shaker. The results presented and the fixture itself serve as a basis for further work and developments.