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Study of rock fracture under blast loading

100%

Baranowski P. , Kucewicz M. , Pytlik M. , Małachowski J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2022

tom Vol. 70, nr 5

art. no. e141723

A study of dolomite rock material failure using a simple small-scale blast setup is presented. Laboratory tests were conducted using disc specimens drilled with a borehole in the center. A detonation cord and a blasting cap were fitted inside the borehole to induce cracking and fracturing of the specimens. The specimens were inserted between two steel plates, which were compressed against the specimen using bolt screws. Prior to testing, the most suitable screw torque for constraining the vertical displacement of the specimen surfaces without compressing the specimen was selected based on numerical simulations. Then, the experimental tests with the blasting cap were simulated using the Johnson–Holmquist II (JH-2) material model, and the properties of the blasting cap were determined and verified in two special tests with a lead specimen. Possessing the validated model, the influence of specimen thickness on the cracking patterns was finally analyzed. This paper presents a relatively easy method for studying rock material behavior under blast loading and for validating the numerical and constitutive models used for rock simulations.

Numerical aspects of modeling flow through the cerebral artery system with multiple small perforators

88%

Tomaszewski M. , Kucewicz M. , Rzepliński R. , Małachowski J. , Ciszek B.

Biocybernetics and Biomedical Engineering

2024

tom Vol. 44, no. 2

341--357

This study investigates the flow and hemodynamics of small perforator blood vessels that branch from the basilar artery (BA) in the brain. Using advanced imaging techniques and computational fluid dynamics (CFD) simulations, detailed 3D geometries of the perforators were acquired through barium contrast injection, micro-CT scans, and data processing. The hybrid geometry, combining micro-CT scans and mesh extraction algorithms, provided accurate vessel models. The influence of different types of finite volume on the analysis was examined, with polyhedral elements showing the most efficient ratio of the analysis time to convergence level. Additionally, the effect of boundary conditions on hemodynamic parameters was studied. Simulations using 0.0 mmHg pressure conditions at the outlets directed flow mainly through the BA, neglecting the perforator branches. In contrast, non-zero outlet pressure conditions significantly increased the flow in the perforators, leading to nonphysiological flow velocities and overestimation of hemodynamic parameters. The assumption of pressure conditions of 0 mmHg at outlets was found to be valid for simple single vessel geometries, but not for more complex vascular systems. This research contributes valuable information on the complex flow patterns and hemodynamics of small perforator blood vessels in the brain and emphasizes the importance of accurately modeling geometry and boundary conditions in such studies.

Technologia CyberOko do diagnozy, rehabilitacji i komunikowania się z pacjentami niewykazującymi oznak przytomności

75%

Czyżewski A. , Odya P. , Szczuko P. , Kostek B. , Kwiatkowska A. , Lech M. , Kucewicz M.

tom nr 3

60--69

CyberOko jest rozwiązaniem opracowanym w Politechnice Gdańskiej, które umożliwia nawiązanie kontaktu i pracę z osobami głęboko upośledzonymi komunikacyjnie. W sposób inteligentny śledzi ruch gałek ocznych, dzięki czemu umożliwia rehabilitację i ocenę stanu świadomości pacjenta nawet w stanie całkowitego porażenia. Rozwiązanie obejmuje także analizę fal EEG, obiektywne badanie słuchu i badanie sygnałów z macierzy elektrod wszczepianych w głąb ludzkiego mózgu. Wspomaga komunikację z pacjentami niewykazującymi oznak przytomności i ich dalszą rehabilitację sposobami umożliwiającymi pokonanie istotnych ograniczeń, jakie mają metody i technologie będące w powszechnym użyciu, tzn. subiektywne skale ocen pacjentów (np. ocena w skali GCS – Glasgow Conciousness Scale), badanie procesów pamięciowych wewnątrz mózgu ludzkiego. Wdrożone urządzenie jest często jedyną szansą dla osoby chorej (np. w stanach podobnych do śpiączki, w przetrwałym stanie wegetatywnym, osoby sparaliżowanej, bez możliwości mówienia), aby mogła ona wyrazić swoje potrzeby.

CyberOko (CyberEye) is a pioneering solution developed at the Gdansk University of Technology enabling contact and work with people with profound communication disabilities. It intelligently tracks eye movements, allowing for rehabilitation and assessment of the patient's state of consciousness even in a state of profound paralysis or locked-in syndrome. The technology engineered also includes the analysis of EEG waves, objective hearing testing, and examination of signals from an array of electrodes implanted deep into the human brain. It supports communication with unconscious patients and their further rehabilitation by means that overcome significant limitations of the methods and technologies in common use, i.e. subjective patient rating scales such as, e.g., Glasgow Conciousness Scale (GCS), study of memory processes inside the human brain. The device implemented is often the only chance for the sick person (e.g., in coma-like states, in a persistent vegetative state, paralyzed, unable to speak) to express their needs.