Metals Abstracts METADEX

Hospitals are compelled to mitigate the frequency and impact of potential failure modes of medical devices, develop an effective maintenance planning strategy, and improve patient satisfaction. This study, therefore, developed a framework that combines resilience principles with fuzzy failure mode and effects analysis (FFMEA) for maintenance planning using the risk Iso-surface method, fuzzy matching sets, and Simulink. The proposed framework used the FFMEA approach to estimate the risk index ( RI ), resilience assessment to obtain the resilience index ( RE ), and developed an RI - RE plot to be used for maintenance planning. The RI estimation of failure modes involved the identification, analysis, and assessment of risk components; severity, occurrence, and detection, utilizing fuzzy logic and matching sets. The RE was measured by four resilience potentials via a survey consisting of 51 questions and then evaluated using fuzzy logic. Finally, the RI - RE plot was divided into 12 zones to determine adequate maintenance strategies for all failure modes. A real case study, which consisted of 22 failure modes for six intensive care unit medical devices, was presented for validation. Results revealed that the developed framework effectively identified adequate resilient maintenance policies with suitable maintenance actions for all failure modes. In conclusion, the framework is found to be valuable and can support maintenance engineering in developing effective maintenance planning for medical devices under fuzzy evaluations and unexpected failure modes.

In this work, a numerical analysis of the mechanics of the interaction of the red blood cell with the vessel wall was carried out. The deformation process is described using an adhesive dissipative elastic model. The influence of the electrostatic double layer and drag force on erythrocyte is investigated. The discrete element method is used to model erythrocyte dynamics. The focus is on the analysis of the effect of different acting forces on the erythrocyte. The results reflect force, displacement, time dependencies. The results indicate the process of erythrocyte deformation before contact, at certain distance from the interacting vessel surface.

The telomere plays an important role to protect chromosomes from interaction with surrounding media as well as its length can be an important factor for the age prediction of an individual. Therefore, fundamental research remains relevant. The given investigation provides a numerical experiment from the mechanics perspective. By applying the DEM, the dynamics of a simplified telomere nucleotide interaction is presented. The applied knowledge is considered from previous investigations where numerical modeling of the dynamics of the interaction of ultrafine objects was analyzed. The nucleotides interaction is modeled based on a Lennard-Jones potential, while for the force-distance relation the presented equations are integrated in time, giving values of distance and velocity in dependence on time. The work outlines the ability to consider the acting force values between nucleotides, taken from known physical experiments on forces. A comparison of different nucleotides interaction, with A/T as well as G/C is also given.

Looking from the mechanical point of view the suspension containing the bacteria may be considered as a system of living active ultrafine particles. Here a model is developed for the interaction of the bacterium in an oblique direction during contact. The model considers an adhesive bacterium moving through a fluid, acting with appropriate specific forces, such as steric, electrostatic double layer and hydrodynamic forces. To understand the influence of the latter hydrodynamic forces on the bacterium, numerical experiments using DEM are carried out with this force and without it. A comparison of these two cases shows the difference in movement.