Megaripple mechanics: bimodal transport ingrained in bimodal sands

Aeolian sand transport is a major process shaping landscapes on Earth and on diverse celestial bodies. Conditions favoring bimodal sand transport, with fine-grain saltation driving coarse-grain reptation, give rise to the evolution of megaripples with a characteristic bimodal sand composition. Here, we derive a unified phase diagram for this special aeolian process and the ensuing nonequilibrium megaripple morphodynamics by means of a conceptually simple quantitative model, grounded in the grain-scale physics. We establish a well-preserved quantitative signature of bimodal aeolian transport in the otherwise highly variable grain size distributions, namely, the log-scale width (Krumbein phi scale) of their coarse-grain peaks. A comprehensive collection of terrestrial and extraterrestrial data, covering a wide range of geographical sources and environmental conditions, supports the accuracy and robustness of this unexpected theoretical finding. It could help to resolve ambiguities in the classification of terrestrial and extraterrestrial sedimentary bedforms.

Mechanical and Micrography Analysis of Armour Plate Weldment Using Tungsten Inert Gas and Oxy-Acetylene Welding Methods

Defence Industries Corporation of Nigeria (DICON) has compared the effect of Tungsten Inert Gas (TIG) and Oxy-Acetylene welding methods on microstructural and some mechanical properties of Armour plate for the modification of military troop carriers. The optical emission spectrometer (OES) at DICON was used to analyse the chemical composition of the armour plate strip. It was then machined and cut to various test piece dimensions for both welding processes, following which the weldment samples were subjected to post-weld mechanical tests (tensile, impact, and hardness) and metallographic examination. The samples were then welded according to the procedure outlined in this study. The fundamental composition of armour plates was preserved in the samples. When compared to Oxy-Acetylene (OA) welding, Tungsten Inert Gas (TIG) welding produced better results, with an average ultimate strength (UTS) of 603.52 MPa and an impact strength of 10.53 J. In addition, the TIG analysis hardness strength for the source material, heat affected zone (HAZ), and weldment sample is 510.3, 502, and 511-HV, respectively. At x200 magnification, the micrography of the TIG weldment revealed a small coarse grain size of ferrite and larger areas of pearlite.

Chemical Classification of Sediments in JVX -Well, Greater Ughelli Depobelt Niger Delta Basin, Nigeria

This study evaluate the Chemical classification of sediments in JVX well, Greater Ughelli Depo belt Niger Delta Basin. Samples collected from different intervals were analyzed using geochemical proxies. Agbada Formation was suggested for the sampled intervals due to the presence of shaleand sand intercalations. lithofacies units gotten from sampled intervals are Sand, Shale and Shaly sand facies . The sands are milky in colour, translucent to opaque, medium to coarse grain, subangular to subrounded and are moderately sorted while the shales are Grey in colour,fissile with the presence of lignite streak and calcareous materials.The geochemical studies of the sediments revealed that SiO2 is the dominant oxide followed by Al2O3 and Fe2O3 which constitutes over 90% while others like CaO, K2O, TiO2, Na2O and MgO constitute 10%. The sediments were classified as Fe-shale, Fe-sand and Quartz arenite. Samples that plotted in the quartz arenites region suggests an intense degree of weathering and reworking. The SiO2/Al2O3 ratios for the sediments in the well are appreciably high indicating that the samples have been heavily weathered, evidenced from the enrichment of quartz and depletion of feldspars. Also, the relatively high concentrations of Fe2O3 and TiO2 is an indication of iron-titanium minerals such as haematite and anatase retiles.

Islands in multiverse models

We consider multiverse models in two-dimensional linear dilaton-gravity theories as toy models of false vacuum eternal inflation. Coupling conformal matter we calculate the Von Neumann entropy of subregions. When these are sufficiently large we find that an island develops covering most of the rest of the multiverse, leading to a Page-like transition. This resonates with a description of multiverse models in semiclassical quantum cosmology, where a measure for local predictions is given by saddle point geometries which coarse-grain over any structure associated with eternal inflation beyond one’s patch.