Lithostratigraphic classification of the Tsodilo Hills Group: a Palaeo- to Mesoproterozoic metasedimentary succession in NW Botswana

The Tsodilo Hills Group strata exposed in the Tsodilo Hills are an association of meta-arenites, meta-conglomerates, quartz-mica schists, sandstone, red siltstone and sedimentary breccia deposited on an open siliciclastic marine shelf between the Late Palaeoproterozic and Late Mesoproterozoic, and outcropping in NW Botswana. The succession is dominated by three micaceous quartzite units interlayered with subordinate lenses and wedges of other rock types. Facies gradients from S to N are expressed by decreasing content of muscovite at all levels of metasediment organisation from thin wedge-shaped units to thick quartzite complexes, as well as a decrease in pebble content and increase in the arenaceous matrix in some metal conglomerate beds, matching regional palaeotransport direction. Well-rounded pebbles of rocks are flat, suggesting redeposition from a beach environment. Lenticular conglomeratic bodies with erosional lower boundaries represent infills of local incisions in the sandy bottom sediments. The abundance of laterally discontinuous lithological units reflects shelf palaeotopography controlled and modified by deposition and migration of large bed forms, ranging from megaripple marks (or submarine dunes) to sand waves. Deposition was influenced by tides and two regressive events. The older regression resulted in a marker unit of tidal mudflat-related red-bed facies: mudstone, siltstone, channel-fill sandstone and sedimentary breccia. The second regression is indicated by a tabular conglomerate marker reflect-ing increased input of coarse terrigenous material.

Development of Voltage Fields in Titanium VT1-0 while Forming a Thin Wedge-Shaped Twin

In the selected treatment modes, a thin wedge-shaped twin was observed, it passed through a section of the crystal with a weak concentration of visible defects. Additional etching of the titanium film revealed an ordered arrangement of dislocations with contrast that appeared on the surface inside the circular sites, which are the stacking faults inside the dislocation loop. The authors provide an explanation of the formation of stacking faults using the detected oscillating contrasts of the faults that are close to the surface. The voltage fields around the wedge-shaped twin, which were constructed with the use of computer simulation, made it possible to determine the value of the elastic stress when it comes into contact with the stopper.

Влияние импульсных скользящих поверхностных разрядов на сверхзвуковое обтекание тонкого клина в ударной трубе

The influence of ~300-ns pulsed sliding surface discharges on supersonic airflow with M = 1.2–1.5 past a thin wedge has been studied in a shock tube at 0.12–0.14 kg/m^3 gas density. It is established that inhomogeneity of the airflow-density field near the wedge leads to changes in the discharge current geometry and the structure of surface-discharge glow. The dynamics of discharge-initiated shock waves disturbing the quasi-stationary flow past the wedge was studied by the method of shadow visualization. It is shown that shock waves from intense surface-discharge channels in front of the wedge and behind its rear part can produce nonstationary action on the flow past the wedge surface, which lasts for up to 120 μs after the discharge pulse.