Rus' military in wars with Polovtsians from mid-11th to the mid-13th century

Celem pracy jest przedstawienie wojskowości ruskiej w walkach z ludem Połowców od połowy XI do połowy XIII wieku. W oparciu o analizę źródeł przedstawione zostały metody odpierania najazdów połowieckich, wyprawy ruskie w stepy oraz taktyka stosowana w bitwach. Przybliżona została także organizacja ruskich i połowieckich sił zbrojnych, a także wzajemne relacje obu stron konfliktu na przestrzeni omawianego okresu.This paper's purpose is to present Rus' military affairs during wars with Polovtsian people from mid-11th to the mid-13th century. Based on the analysis of the sources methods of defence against Polovtsian invasions, Rus' expeditions and battle tactics were presented. Also organisation of Rus' and Polovtsian armies was brought closer, as well as their relations during described period

Mercenaries in Rus' during the 9th-12th century

Celem niniejszej pracy jest poddanie analizie wzmianek źródłowych mogących świadczyć o obecności najemników na służbie władców ruskich od połowy IX wieku do końca XII wieku. Na ile pozwalają na to przekazy źródłowe, dokonano próby rozdzielenia przypadków służby najemniczej od sił zbrojnych działających jako wsparcie sojusznicze. Omówiona została rola i liczebność najemników w konfliktach, a także metody ich najmowania oraz opłacania przez Rurykowiczów. Praca jest podzielona według wyróżnienia trzech grup najemników: skandynawskich Waregów, koczowników ze stepów oraz wojowników zachodnich.The purpose of this work is to analyse sources which can confirm presence of mercenaries at the Russian rulers' services since half of 9th century to the end of 12th century. There was a try to separate cases of mercenary services from situations when foreign soldiers were fighting as support of ally. In the text, there is a discussion about the role and number of mercenaries in the conflicts and also about their methods of hiring and paying them. The work is divided into three chapters according to division mercenaries in three groups: Scandinavian Varangians, steppe nomads and warriors from the West

Data supplementary to the paper 'Influence of slope incline on the ejection of two-phase soil splashed material'

The results are related with experiments of soil splash phenomenon on simulated slope samples affected by single drop impact. The dataset contains 1) raw data with measured quantitites (mass of ejected material) and 2) Supplementary Material for the paper (detailed statistical analysis).More details are available in README file.</p

Soil Deformation after Water Drop Impact—A Review of the Measurement Methods

Water erosion is an unfavorable phenomenon causing soil degradation. One of the factors causing water erosion is heavy or prolonged rainfall, the first effect of which is the deformation of the soil surface and the formation of microcraters. This paper presents an overview of research methods allowing the study of microcraters as well as the process of their formation. A tabular summary of work on the measurements of various quantities describing the craters is presented. The said quantities are divided into three groups: (i) static quantities, (ii) dynamic quantities, and (iii) dimensionless parameters. The most important measurement methods used to study crater properties, such as (i) basic manual measurement methods, (ii) photography, (iii) high-speed imaging, (iv) profilometers, (v) 3D surface modelling, and (vi) computed tomography (CT) and its possibilities and limitations are discussed. The main challenges and prospects of research on soil surface deformation are also presented

Splash erosion and surface deformation following a drop impact on the soil with different hydrophobicity levels and moisture content.

The splash phenomenon and the scale of the surface deformation of post-fire soils in the variants of various hydrophobicity and moisture content were studied. Splash erosion is the result of the impact of a single water drop and was analysed using high-speed cameras, while the surface deformation was parameterized using a structured light scanner. The extremely water-repellent variant (dry_V) showed distinct differences, expressed primarily in the number of ejected particles, which was 2.5 times higher than in the four soils with lower levels of hydrophobicity. It was also observed that as a result of the drop impact onto an extremely hydrophobic soil surface, a form known as liquid marble was created inside the crater. Soil moisture content determined the manner, scale and dynamics of the splash erosion. In the case of wet soils, the phenomenon proceeded up to five times faster, and as a result of the drop impact, a large number of fine particles were ejected, which reached nearly twice the velocities and three times the displacement distances compared to the dry soil group. However, the particles and/or aggregate splashed on the dry samples were larger, which also translated into the formation of craters up to twice as extensive as those in the wet soils

The static parameters of the crown.

<p>S–spread, H–height, D–diameter, h_unbr−height of unbroken part of crown, d_b−base diameter.</p

Times of crown’s growth up and breaking up on the saturated soil surface and water layer on the smooth surface.

<p>Times of crown’s growth up and breaking up on the saturated soil surface and water layer on the smooth surface.</p

The differences in crown formation during the splash on the thin water layers formed on the saturated soil surface and model surface - Fig 6

<p><b>The velocities of (A) crown rising (vertical velocity) and (B) crown spreading (horizontal velocity) for the saturated soil and water layer</b>.</p

Comparison of crown shapes at different time intervals.

<p>(t₁ = 0.92 ms, t₂ = 1.53 ms, t₃ = 3.06 ms, t₄ = 7.65 ms) Time intervals after the drop impact from 1.5 m height for: (a) crown on soil surface; (b) crown on water layer.</p