Retarding of Precipitation Hardening of Al-Cu Alloy by Cadimium Addition

The aim of the present work is to prepare a set of Al-Cu alloys with slow precipitation hardening by aging. Present work results can be utilized during the importing or exporting of such alloys at solution treatment conditions. In order to establish this aim, a set of Al-4%Cu alloys have been prepared in the laboratory to investigate the effect of Cd-addition with the percentage varied from (0.1, 0.3 and 0.5) weight percentage. The prepared alloys with different Cd additions were subjected to a natural aging up to 60 days after solution treatment. As a result, the alloys showed an obvious retarding in the aging kinetics as the percentage of Cdadditions increasing. This retarding was found to be due to the trapping of the vacancies that resulted during the quenching step that resulted in delays of Gunier- Preston zones precipitation. SEM has been used in monitoring of microstructure as well as optical microscop

Silicone rubber‐nanoceramic composites for 5G antenna substrates

Abstract Here, the eligibility of silicone rubber‐nanoceramic composites as flexible substrates for sub‐6 GHz 5G antennas is investigated. Two different composites are prepared using the solution mixing method, namely mono and hybrid composites. The reflection and transmission coefficient (S‐parameters) of composites are measured using a rectangular waveguide‐based transmission line technique in conjunction with a Vector Network Analyzer (VNA) at C‐band frequencies (4–8 GHz). The Nicolson–Ross–Weir (NRW) algorithm is adopted to extract the complex permittivity and loss tangent of the material under test. Due to the synergetic effect, the silicone rubber hybrid composite (0.12BiVO4+0.12LaNbO4) exhibits the advantage of a lowered loss tangent while retaining a good dielectric constant at 5.78 GHz. A rectangular microstrip patch antenna is designed and simulated with CST software using 0.12BVO/0.12LNO/0.76SR composite as a substrate. Moreover, based on the simulation, the antenna with the proposed substrate has acceptable performance at 5.78 GHz with the return loss, directivity, and gain of −25.05 dB, 5.46 dBi and 2.74 dBi, respectively. As a result, the composite material's ability to act as a suitable substrate for a 5 GHz Wi‐Fi antenna is confirmed

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population