ALBERT

Description: In the conceptual aircraft design phase, prediction of the empty weight typically relies on empirically-based regression equations which execute quickly and require little detailed information about the internal structural layout. Since they are based on existing aircraft, however, empirical methods can lose their validity for newer technologies and unconventional configurations. Designers can transition to higher-order, physics-based analysis methods to improve the accuracy of the weight prediction, but at the cost of complex model setup and increased computational time. This paper describes a methodology for low-order aero-structural analysis of conceptual aircraft configurations that increases the use of physics-based analysis in conceptual design, but is less complex and time-consuming than higher-order methods such as finite-element analysis. The methodology uses Vehicle Sketch Pad (OpenVSP) to model the aircraft geometry, and ASWING to perform the aero-structural analysis. The internal forces and moments from the ASWING analysis are post-processed to calculate the resulting direct and shear stresses in the structure, and the thickness distributions of the aircraft components are varied to match the maximum von Mises stress at each cross section to the material allowable. To offset the increased computational time relative to empirical weight equations, a process is studied which uses parametric variation to develop a regression equation relating the weight of the aircraft wing to major design variables. This new weight equation is similar to existing empirical equations, but is built using the more physics-based methodology; the new equation could be used to augment or replace portions of the empirical database to improve the validity of the wing weight prediction for unconventional configurations and advanced technologies.

Description: The Atmospheric Correction Inter-comparison eXercise (ACIX) is an international initiative with the aim to analyse the Surface Reflectance (SR) products of various state-of-the-art atmospheric correction (AC) processors. The Aerosol Optical Thickness (AOT) and Water Vapour (WV) are also examined in ACIX as additional outputs of AC processing. In this paper, the general ACIX framework is discussed; special mention is made of the motivation to initiate the experiment, the inter-comparison protocol, and the principal results. ACIX is free and open and every developer was welcome to participate. Eventually, 12 participants applied their approaches to various Landsat-8 and Sentinel-2 image datasets acquired over sites around the world. The current results diverge depending on the sensors, products, and sites, indicating their strengths and weaknesses. Indeed, this first implementation of processor inter-comparison was proven to be a good lesson for the developers to learn the advantages and limitations of their approaches. Various algorithm improvements are expected, if not already implemented, and the enhanced performances are yet to be assessed in future ACIX experiments.

Description: Megacrystic zircon grains from alkaline basaltic fields are rare but can provide fundamental insights into mantle metasomatic processes. Here, we report in-situ U-Pb ages, trace element concentrations and hafnium and oxygen isotopes for fourteen zircon megacrysts from two intraplate alkaline basalt locations in New Zealand. U-Pb ages indicate the zircons crystallised between 12.1 and 19.8 Ma. Zircon oxygen isotopic compositions range from low to mantle-like compositions (grain average δ18O = 3.8–5.1‰). Hafnium isotopes (εHf(t) = +3.3 to +10.4) mostly overlap with intraplate mafic rocks and clinopyroxene in metasomatized peridotitic mantle xenoliths but show no correlation with most trace element parameters or oxygen isotopes. The zircons are interpreted to have formed by the reaction between low-degree melts derived from pre-existing mantle metasomes and the depleted mantle lithosphere prior to eruption and transport to the surface. The low Hf concentration, an absence of Eu anomalies, and elevated U/Yb compared to Nb/Yb in the megacrystic zircons are interpreted to show that the source metasomes comprised subduction- and carbonatite-metasomatised lithospheric mantle. As these trace element characteristics are common for megacrystic zircon in intra-plate basaltic fields globally, they suggest the prevalence of subduction- and carbonatite-metsasomatised mantle under these intraplate volcanic regions. The unusually low δ18O was likely present prior to metasomatic enrichment and may have resulted from high-temperature hydrothermal alteration during initial mantle lithosphere formation at a mid ocean ridge or, possibly, during subduction-related processes associated with continent formation. The combination of proportionally varied contributions from carbonatite- and subduction-metasomatised lithospheric melts with asthenospheric melts may explain the variety of primitive intraplate basalt compositions, including low δ18O reported for some local intraplate lavas.