СУЧАСНІ АСПЕКТИ РОЗВИТКУ КОАГУЛОПАТІЇ У ПАЦІЄНТІВ ПРИ COVID‑19 ІНФЕКЦІЇ: ОГЛЯД ЛІТЕРАТУРИ

This review summarizes current knowledge about coagulation disorders associated with COVID-19 infection. Despite a significant amount of research, it is currently unclear whether COVID-19 is the direct cause of coagulopathic disorders or they occur as the infectious process progresses. Different authors have proposed several pathogenetic mechanisms for the development of coagulopathy in this disease. However, the most important is the release of a large number of cytokines that provoke interstitial inflammation, endothelial damage and activation of coagulation, in the pathogenesis of which the tissue factor plays a key role. Hyperinflammatory reactions lead to tissue damage, disruption of the endothelial barrier and uncontrolled activation of coagulation. In the lungs and, possibly, in other organs, under the influence of the virus, local damage to the vascular endothelium occurs, which leads to angiopathy, activation and aggregation of platelets with the formation of blood clots and concomitant consumption of platelets. Systemic hypercoagulation and hyperfibrinogenemia significantly increase the likelihood of large vessel thrombosis and thromboembolic complications, which are detected in 20–30% of patients in the intensive care units. Along with an increase in the level of cytokines in the blood, their content also increases in the lungs and in the bronchoalveolar lavage fluid. Cytokine storm leads to systemic intravascular coagulation, multiple organ failure and death. The review also provides the rationale for the principles of managing patients with coagulopathy based on the known mechanisms of unique disorders inherent in COVID-19. It has been shown that the problem of the pathogenesis of the development of blood clotting disorders in COVID-19 infection remains relevant.

Influence of Failure Criteria and Intralaminar Damage Progression Numerical Models on the Prediction of the Mechanical Behavior of Composite Laminates

This work evaluates the effectiveness of commonly adopted local damage evolution methods and failure criteria in finite element analysis for the simulation of intralaminar damage propagation in composites under static loading conditions. The proposed numerical model is based on a User Defined Material subroutine (USERMAT) implemented in Ansys. This model is used to predict the evolution of damage within each specific lamina of a composite laminate by introducing both sudden and gradual degradation rules. The main purpose of the simulations is to quantitatively assess the influence of the adopted failure criteria in conjunction with degradation laws on the accuracy of the numerical predictions in terms of damage evolution and failure load. The mechanical behavior of an open hole tension specimen and of a notched stiffened composite panel under shear loading conditions have been numerically simulated by Progressive Damage Models (PDM). Different failure criteria have been implemented in the developed Ansys USERMAT, together with sudden and gradual degradation rules based on the Continuum Damage Mechanics (CDM) approach. Numerical results have been validated against experimental data to assess the effects of the different failure criteria and damage evolution law on the global mechanical response and local damage predictions in composite laminates.

Safety Evaluation of Arch Dam Subjected to Underwater Contact Explosion

The stability of an arch dam can be significantly damaged by an extreme underwater explosion. This study proposed a damage index for assessing the degree of local damage of an arch dam after the dam was subjected to an underwater explosion. The damage index was applied to assess local damage at the middle part of the dam, surcharge holes, and abutment. A model was developed to evaluate the stability of the entire dam based on the spatial distribution of damage and the damage on the base interface. Results showed that local explosion damage at flood discharge holes or abutments might cause instability of the arch dam. When the contact explosion action location is on the abutment, it only needs 310 kg to cause the overall damage of the arch dam, while when the action location is on the middle part of the dam, the quantity of explosive required is 2800 kg.

Implementation of a damage calculation in a numerical wheel-rail contact simulation

Railways can transport cargo and persons a great distance. The combination of high axle loads, and the rigid wheels and rails made of steel results in high stresses at the wheel-rail contact. These high stresses cause rolling contact fatigue. To prevent and to forecast the rolling contact fatigue, the knowledge of the stresses and their effect on the local damage are important. One possible way to achieve results of the stresses is based on a finite element analysis. The calculation of the rolling contact fatigue is conducted subsequently. This paper will present one possibility to implement the damage calculation into a finite element software and use the post-processing to enable a fast assessment of rolling contact fatigue on the surface and the adjacent volume of a rail.