Structural damage detection using auto correlation functions of vibration response under sinusoidal excitation
Structural damage detection using time domain vibration responses has attracted more and more researchers in recent years because of its simplicity in calculation and no requirement of a finite element model. This paper proposes a new approach to locate the damage using the auto correlation function of vibration response signals under sinusoidal excitation from different measurement points of the structure, based on which a vector named Auto Correlation Function at Maximum Point Value Vector (AMV) is formulated. A sensitivity analysis of the normalized AMV with respect to the local stiffness shows that under several specific frequency excitations, the normalized AMV has a sharp change aroun…
A comparative molecular dynamics-phase-field modeling approach to brittle fracture
Abstract In this work, a novel comparative method for highly brittle materials such as aragonite crystals is proposed, which provides an efficient and accurate in-sight understanding for multi-scale fracture modeling. In particular, physically-motivated molecular dynamics (MD) simulations are performed to model quasi-static brittle crack propagation on the nano-scale and followingly compared to macroscopic modeling of fracture using the phase-field modeling (PFM) technique. A link between the two modeling schemes is later proposed by deriving PFM parameters from the MD atomistic simulations. Thus, in this combined approach, MD simulations provide a more realistic meaning and physical estima…
A comparative study of mechanical properties of fresh and frozen-thawed porcine intervertebral discs in a bioreactor environment
Abstract Limited availability of fresh intervertebral discs (IVDs) necessitates the use of frozen-thawed samples in biomechanical investigations. Several authors have reported the mechanical properties of frozen-thawed IVDs, but few studies have investigated the effects of storage temperature and cooling rate. The validity and reliability of the applied freezing-thawing procedures are still relatively unknown. The study aims to compare the mechanical responses of fresh porcine IVDs and porcine IVDs, which were frozen at different freezing temperatures with a controlled-rate cooling process and then thawed. The specimens were obtained from pigs aged 6 months. A total of 18 functional spine u…
Teaching Green Analytical Chemistry on the Example of Bioindication and Biomonitoring (B & B) Technologies
Teaching of Green Analytical Chemistry (GAC) requires a not inconsiderable willingness on the part of the lecturer to familiarize himself with a relatively new field in analytical chemistry. Although there is much that can be derived from Green and Sustainable Chemistry, the GAC’s forward-looking perspectives in particular are independent approaches that must not be neglected. In the first chapter of this article, approaches are pursued “how (teachers) learn to learn,” ultimately based on a consensus on ethics, which allows dealing with people, society and the environment to become an interdisciplinary unit. The end of all this is a smart method of conflict management which provides solutio…
Coupled Multi-Field Continuum Methods for Porous Media Fracture
The focus of the present contribution is on the numerical modelling of hydraulic fracture in fluid-saturated heterogeneous materials, which can be carried out on a macroscopic scale using extended continuum porous media theories. This accounts for the crack nucleation and propagation, deformation of the solid matrix and change in the flow of the interstitial fluid. In particular, fluid-saturated porous materials basically represent volumetrically interacting solid-fluid aggregates, which are modelled using the Theory of Porous Media. The hydraulic- or tension-induced fracture occurs in the solid matrix and is simulated using a diffusive phase-field modelling approach. This way of fracture t…
Quantitative relations between different concentrations of micro- and macroelements in mosses and lichens: the region of Opole (Poland) as an environmental interface in between Eastern and Western Europe
We examined the concentration of selected metals: Al, Mn, Fe, Cu, Zn, Cd and Pb, as well as activity of 137Cs in samples of moss and lichen, collected in the area surrounding Bory Stobrawskie, a wood complex situated in southern Poland. The concentration of metals was determined by atomic absorption spectrometry. The activity of 137Cs was determined by gamma spectrometry. We used these results, as well as results published in the literature, to determine the correlation between the concentration of analytes in lichens and in mosses. The analysis of the function ln(cx,moss) = lna + bln(cx,lichen) indicated with high degree of certainty that the concentration levels of analytes accumulated in…