Abstract
Aircraft produce condensation trails, which are thought to increase high-level cloudiness under certain conditions. However the magnitude of such an effect and whether this contributes ...substantially to the radiative forcing due to the aviation sector remain uncertain. The very substantial, near-global reduction in air traffic in response to the COVID-19 outbreak offers an unprecedented opportunity to identify the anthropogenic contribution to the observed cirrus coverage and thickness. Here we show, using an analysis of satellite observations for the period March–May 2020, that in the 20% of the Northern Hemisphere mid-latitudes with the largest air traffic reduction, cirrus fraction was reduced by ∼9 ± 1.5% on average, and cirrus emissivity was reduced by ∼2 ± 5% relative to what they should have been with normal air traffic. The changes are corroborated by a consistent estimate based on linear trends over the period 2011–2019. The change in cirrus translates to a global radiative forcing of 61 ± 39 mW m
−2
. This estimate is somewhat smaller than previous assessments.
•Discovering the exact jet fuel chemical composition.•Overview of chemical composition-property correlation techniques from 1955 to 2019.•Four categories: NMR spectroscopy, IR spectroscopy, Raman ...spectroscopy, and gas chromatography.•Comparison via coefficient of determination and measure of the uncertainty of future predictions.
The fuel certification process is a necessary step for all aviation fuels before deployment. This approval process is composed of multiple fuel physiochemical properties (e.g., density, viscosity, flash point, freezing point, etc.) testing. Measuring fuel properties is a very time consuming and cost-intensive process. Thus, having a tool capable of predicting fuel properties based on a small amount of fuel, utilizing fuel chemical composition, would be of essential value for an increased incentive towards a long-lasting renewable jet fuel production. The first step in achieving this is discovering the detailed chemical composition. The consecutive step is the development of predictive models that correlate the fuel chemical composition to the fuel physiochemical properties. This review provides an overview of correlation techniques and methods (from 1955 to 2019) organized according to four main categories: NMR spectroscopy (alone and in combination with chromatographic techniques), IR spectroscopy (NIR and FTIR), Raman spectroscopy, and gas chromatography (one-dimensional and two-dimensional). These techniques and their predictive capability were compared according to several criteria, specifically: the coefficient of determination (R2) and the measure of the uncertainty of future predictions, which includes standard deviation of residuals, root-mean-square-error (RMSE), root-mean-square-error of prediction (RMSEP), standard error of prediction (SEP), root-mean-square-error of cross-validation (RMSECV), mean absolute error (MAE), and mean absolute percentage error (MAPE). In conclusion, this work summarizes an in-depth review of all the accomplishments as well as the challenges required to be overcome in the field of accurately correlating chemistry to fuel properties.
Glaucoma in U.S. Civil Aviation: 2005-2014 DeJohn, Charles A.; Mills, William D.
Aerospace medicine and human performance,
12/2017, Volume:
88, Issue:
12
Journal Article
Peer reviewed
INTRODUCTION: Until recently, glaucoma requiring treatment was disqualifying for U.S. pilots and required an aeromedical special issuance waiver. Since 2013 Aerospace Medical Examiners (AMEs) have ...been authorized to evaluate third-class pilots with mild glaucoma using similar
protocols and issue medical certificates without a waiver if these criteria specified in the AME Guide are met.METHODS: The FAA's medical database was searched for pilots with glaucoma between 2005 and 2014. The National Transportation Safety Board (NTSB) accident database
was then searched to determine which pilots with glaucoma had aircraft accidents during that period. The odds of accidents in the glaucoma pilots were compared with the overall pilot accident odds.RESULTS: Of 5000 pilots being treated for glaucoma, 78 were involved in aircraft accidents;
however, glaucoma was not cited as the probable cause or contributing factor in any of the accidents. A logistic regression model adjusted for age showed that glaucoma had a protective effect on accident odds. The crude accident rate for third-class pilots with glaucoma was estimated to be
7.2 per 100,000 flight hours, with a fatal accident rate of 1.8 per 100,000. Although these point estimates were slightly higher than the estimated general aviation accident rates, the differences were not statistically significant.DISCUSSION: These findings suggest that third-class
pilots with glaucoma are not at significantly greater risk of an accident than the U.S. general aviation community. It also indicates that FAA certification protocols for certifying and following pilots with glaucoma provide an adequate level of flight safety.DeJohn CA, Mills WD. Glaucoma in U.S. civil aviation: 2005-2014. Aerosp Med Hum Perform. 2017; 88(12):1117-1122.
The importance of geographical proximity for interaction and knowledge sharing has been discussed extensively in recent years. There is increasing consensus that geographical proximity is just one ...out of many types of proximities that might be relevant. We argue that proximity may be a crucial driver for agents to connect and exchange knowledge, but too much proximity between agents on any of the dimensions might harm their innovative performance at the same time. In a study on knowledge networks in the Dutch aviation industry, we test this so-called proximity paradox empirically. We found evidence that the proximity paradox holds to a considerable degree. Our study clearly showed that cognitive, social, organizational and geographical proximity were crucial for explaining the knowledge network of the Dutch aviation industry. However, we found strong evidence that too much cognitive proximity lowered firms’ innovative performance, and organizational proximity did not have an effect.
The applications of Additive Manufacturing (AM) have been grown up rapidly in various industries in the past few decades. Among them, aerospace has been attracted more attention due to heavy ...investment of the principal aviation companies for developing the AM industrial applications. However, many studies have been going on to make it more versatile and safer technology and require making development in novel materials, technologies, process design, and cost efficiency. As a matter of fact, AM has a great potential to make a revolution in the global parts manufacturing and distribution while offering less complexity, lower cost, and energy consumption, and very highly customization. The current paper aims to review the last updates on AM technologies, material issues, post-processes, and design aspects, particularly in the aviation industry. Moreover, the AM process is investigated economically including various cost models, spare part digitalization and environmental consequences. This review would be helpfully applied in both academia and industry as well.
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