Simulation of the Crack Growth Under Mixed-mode Loading: Fracture Criteria and Molecular Dynamics Approach

The crack propagation direction angle is investigated by the use of two approaches. The first one is based on the classical mathematical theory of brittle fracture and the Williams series expansion of the stress field at the vicinity of the crack tip. The second approach is based on the molecular dynamics method. Atomistic simulations of the central crack growth process in a plane medium using Large-scale Molecular Massively Parallel Simulator (LAMMPS), a classical molecular dynamics code, are performed. The inter-atomic potential used in this investigation is Embedded Atom Method (EAM) potential. The specimens with initial central crack were subjected to Mixed-Mode loadings. The simulation cell contains 400000 atoms. The crack propagation direction angles under different values of the mixity parameter in a wide range of values from pure tensile loading to pure shear loading in a wide diapason of temperatures (from 0.1 К to 800 К) are obtained and analyzed. It is shown that the crack propagation direction angles obtained by molecular dynamics method coincide with the crack propagation direction angles given by the multi-parameter fracture criteria based on the strain energy density and the multi-parameter description of the crack-tip fields

Optimizing the Conditions of Mechanochemical Synthesis of LiAl Layered Hydroxides

AbstractLiAl layered double hydroxides (LDH) are the promising compounds for application in base catalysis and as precursors of the supports for platinum catalysts. In the work, such systems were synthesized by mechanochemical method. The effect of composition of the initial mixture (Al(OH)3, Al(NO3)3, LiOH, LiNO3), material of milling bodies (steel or ceramic), and activation conditions (centripetal acceleration and activation time) on the properties of LiAl-LDH were studied. It was found that each of the synthesized systems is a polyphase one and contains not only the LDH phase but also the side phase of aluminum trihydroxide. In addition, the samples obtained with the use of steel milling bodies have a substantial amount of iron. The use of ceramic milling bodies makes it possible to obtain the LiAl-LDH phase under relatively mild conditions (acceleration of 300 m/s2 and activation time of 15min)

Competitive success factors of forwards in elite water polo

Objective of the study was to rate the forwards' swimming techniques versus the competitive success rates in the water polo teams. The authors made a content analysis of the 2016 Olympics video replays with application of the qualitative and quantitative performance rates to analyze the competitive swimming techniques and game tactics of the leading forwards. It was found that the team competitive performance may be rated by the following criteria: (1) team standing on the tournament scoreboard; (2) goals scored; and (3) goals conceded. The study data were processed using the data averaging, correlation and factor analyses to offer a statistical model of the competitive swimming techniques applied by the elite water polo players. The study findings were used to offer the sets of swimming skills training exercises to model competitive performance of the elite forwards in water polo. © 2018 Teoriya i praktika fizicheskoy kul'tury i sporta. All rights reserved

Competitive swimming styles applied by elite water-polo players

Subject to the study were the elite water-polo players' competitive swimming styles and their relative application rates versus the players' game roles in top-ranking competitions. Qualitative and quantitative input data for the study was provided by the content analysis of video replays of 43 matches at the 2016 Olympic Games in Rio de Janeiro with participation of the national teams of Greece, Japan, Australia, Brazil, Hungary, Croatia, Serbia, Montenegro, Italy, Spain, France and the USA. Subject to the content analysis were the competitive swimming style elements (units) and their application rates versus the players' game roles (defenders, utility forwards, wing forwards), the styles and their shares being rated in the relevant units - seconds, meters and game role ratios. The study data and analyses provided a set of reference points for the swimming practices modelling the elite players' competitive swimming styles. The study findings on the elite water-polo players' competitive swimming styles and their relative application rates may be applied for reference in the swimming training systems being designed for water-polo players of different skill levels

Competitive success factors of forwards in elite water polo

Objective of the study was to rate the forwards' swimming techniques versus the competitive success rates in the water polo teams. The authors made a content analysis of the 2016 Olympics video replays with application of the qualitative and quantitative performance rates to analyze the competitive swimming techniques and game tactics of the leading forwards. It was found that the team competitive performance may be rated by the following criteria: (1) team standing on the tournament scoreboard; (2) goals scored; and (3) goals conceded. The study data were processed using the data averaging, correlation and factor analyses to offer a statistical model of the competitive swimming techniques applied by the elite water polo players. The study findings were used to offer the sets of swimming skills training exercises to model competitive performance of the elite forwards in water polo. © 2018 Teoriya i praktika fizicheskoy kul'tury i sporta. All rights reserved

Competitive swimming styles applied by elite water-polo players

Subject to the study were the elite water-polo players' competitive swimming styles and their relative application rates versus the players' game roles in top-ranking competitions. Qualitative and quantitative input data for the study was provided by the content analysis of video replays of 43 matches at the 2016 Olympic Games in Rio de Janeiro with participation of the national teams of Greece, Japan, Australia, Brazil, Hungary, Croatia, Serbia, Montenegro, Italy, Spain, France and the USA. Subject to the content analysis were the competitive swimming style elements (units) and their application rates versus the players' game roles (defenders, utility forwards, wing forwards), the styles and their shares being rated in the relevant units - seconds, meters and game role ratios. The study data and analyses provided a set of reference points for the swimming practices modelling the elite players' competitive swimming styles. The study findings on the elite water-polo players' competitive swimming styles and their relative application rates may be applied for reference in the swimming training systems being designed for water-polo players of different skill levels

Clinical and Anamnestic Features of Pathology of Gastrointestinal Tract in Children with Syndrome of Heart Connective Tissue Dysplasia, Born to Parents Irradiated In Childhood due to the Chernobyl Accident

The children born to parents irradiation-exposed in childhood due to the Chernobyl accident were found to have mainly the upper gastrointestinal pathology, namely chronic gastroduodenitis, usually concomitant, and several areas of the alimentary canal being involved into the pathological process. The children with the syndrome of heart connective tissue dysplasia have earlier manifestation of the upper gastrointestinal diseases (from pre-school age) and with age systemic damage of various organs and systems is noted, as evidenced by such indicators as a number of clinical entities per child (among the children of the I group — 6.8; II group — 4.9). The analysis of biomedical risk factors and index of burdened familial history on gastrointestinal pathology in I–II degree relatives did not demonstrate a significant difference between the groups. The clinical manifestations of chronic upper gastroduodenal diseases in children with the syndrome of heart connective tissue dysplasia typically have more frequent exacerbations due to the psycho-emotional and physical exhaustion. These children more often have moderate periodic pain; higher occurence of gastric dyspepsia symptoms, intestinal motor dysfunction and concomitant nervous system disorders (80.0 %) and chronic foci of infection (62.2 %)

Is testosterone responsible for athletic success in female athletes?

© 2020 ediZioNi MiNerVa Medica BacKGrouNd: The aim of this study was to determine the interrelationship between the resting serum testosterone (T) levels of female athletes from different types of sporting events and their athletic success. MeThodS: The study involved 599 russian international-level female athletes (95 highly elite, 190 elite, and 314 sub-elite; age: 16-35 years) and 298 age-matched female controls. The athlete cohort was stratified into four groups according to event duration, distance, and type of activity: 1) endurance athletes; 2) athletes with mixed activity; 3) speed/strength athletes; 4) sprinters. athletic success was measured by determining the level of achievement of each athlete. reSulTS: The mean T levels of athletes and controls were 1.65±0.87 and 1.76±0.6 nmol/l (p=0.057 for difference between groups) with ranges of 0.08-5.82 and 0.38-2.83 nmol/l in athletes and controls, respectively. T levels were positively associated with athletic success in sprinters (p=0.0002 adjusted for age) only. Moreover, none of the sub-elite sprinters had T>1.9 nmol/l, while 50% of elite and highly elite sprinters had T>1.9 nmol/l (or=47.0; p<0.0001). CONCLUSIONS: Our data suggest that the measurement of the serum T levels significantly correlates with athletic success in sprinters but not other types of athletes and in the future may be useful in the prediction of sprinting ability