Characteristics Of Large Aspect Angle Vhf Radar Echoes In The Presence And Absence Of Optical Aurora

For many years, researchers have been puzzled by the occurrence of strong, large aspect angle radar auroral echoes. Strong aspect sensitivities of up to 10 dB per degree have been observed at small aspect angles while large aspect angle measurements show much weaker and highly variable aspect sensitivities. It is the purpose of this thesis to attempt to understand the different results at the large aspect angles.;For this study, data from the radars and optical instruments of the CANOPUS ground based system in central Canada have been examined. The two radars (the BARS radars) operate at VHF (48.5 MHz) and have large aspect angles. A statistical study of the spatial relationship between the radar echoes and the optical aurora during 13 hours was performed. Also, data from the radar during daylight periods were examined for evidence of aspect sensitivity.;The most noticeable observation of the statistical study was that there was a strong tendency for the radar echoes to occur on the side of the optical aurora remote from the radar. This results is shown to be consistent with refraction reducing the apparently large aspect angles.;For the daylight periods, a self-consistent study found an aspect sensitivity which varied from 8 dB per degree at an aspect angle of 4.5{dollar}\sp\circ{dollar} down to about 4 dB per degree at an aspect angle of 6{dollar}\sp\circ{dollar}. These aspect sensitivities are in agreement with experiments at small aspect angles and higher frequencies.;This study has found two strikingly different kinds of large aspect angle echoes. The strongest echoes occurred on the remote side of optical features and generally had strong echo powers and strong echo power dependence on flow angle. The other type of echoes were the actual large aspect angle echoes which had moderate to weak powers and weak or non-existent flow angle dependence

Integrating aerodynamics and structures in the minimum weight design of a supersonic transport wing

An approach is presented for determining the minimum weight design of aircraft wing models which takes into consideration aerodynamics-structure coupling when calculating both zeroth order information needed for analysis and first order information needed for optimization. When performing sensitivity analysis, coupling is accounted for by using a generalized sensitivity formulation. The results presented show that the aeroelastic effects are calculated properly and noticeably reduce constraint approximation errors. However, for the particular example selected, the error introduced by ignoring aeroelastic effects are not sufficient to significantly affect the convergence of the optimization process. Trade studies are reported that consider different structural materials, internal spar layouts, and panel buckling lengths. For the formulation, model and materials used in this study, an advanced aluminum material produced the lightest design while satisfying the problem constraints. Also, shorter panel buckling lengths resulted in lower weights by permitting smaller panel thicknesses and generally, by unloading the wing skins and loading the spar caps. Finally, straight spars required slightly lower wing weights than angled spars

Early respiratory viral infections in infants with cystic fibrosis

This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Background Viral infections contribute to morbidity in cystic fibrosis (CF), but the impact of respiratory viruses on the development of airway disease is poorly understood. Methods Infants with CF identified by newborn screening were enrolled prior to 4 months of age to participate in a prospective observational study at 4 centers. Clinical data were collected at clinic visits and weekly phone calls. Multiplex PCR assays were performed on nasopharyngeal swabs to detect respiratory viruses during routine visits and when symptomatic. Participants underwent bronchoscopy with bronchoalveolar lavage (BAL) and a subset underwent pulmonary function testing. We present findings through 8.5 months of life. Results Seventy infants were enrolled, mean age 3.1 ± 0.8 months. Rhinovirus was the most prevalent virus (66%), followed by parainfluenza (19%), and coronavirus (16%). Participants had a median of 1.5 viral positive swabs (range 0–10). Past viral infection was associated with elevated neutrophil concentrations and bacterial isolates in BAL fluid, including recovery of classic CF bacterial pathogens. When antibiotics were prescribed for respiratory-related indications, viruses were identified in 52% of those instances. Conclusions Early viral infections were associated with greater neutrophilic inflammation and bacterial pathogens. Early viral infections appear to contribute to initiation of lower airway inflammation in infants with CF. Antibiotics were commonly prescribed in the setting of a viral infection. Future investigations examining longitudinal relationships between viral infections, airway microbiome, and antibiotic use will allow us to elucidate the interplay between these factors in young children with CF

Application of multidisciplinary optimization methods to the design of a supersonic transport

An optimization design method is discussed. This method is based on integrating existing disciplinary analysis and sensitivity analysis techniques by means of generalized sensitivity equations. A generic design system implementing this method is described. The system is being used to design the configuration and internal structure of a supersonic transport wing for optimum performance. This problem combines the disciplines of linear aerodynamics, structures, and performance. Initial results which include the disciplines of aerodynamics and structures in a conventional minimum weight design under static aeroelastic constraints are presented