1. Behaviour of cellular metamaterials under impact loading conditions : doctoral disertationYunus Emre Yilmaz, 2024, doktorska disertacija Opis: This doctoral thesis investigates cell-size-graded metallic and non-metallic Triply Periodic
Minimal Surface (TPMS) structures' behavior under varying loading rates. Using experimental
tests, analytical calculations, and advanced computer simulations, the research explores the
interplay between material properties, cell size grading, and deformation mechanisms under
different strain rates. The study focuses on enhancing the Direct Impact Hopkinson Bar (DIHB)
setup for accurate force and displacement measurements and pioneering a method for
quantifying inertial forces, critical at high strain rates.
Key findings show that cell-size grading significantly affects deformation patterns, with initial
deformation occurring in regions with smaller and lower stiffness cells across different loading
rates and TPMS geometries. The research also highlights topology's influence on mechanical
response, with photopolymer-based diamond structures showing superior energy absorption
and gas-atomized steel structures favoring gyroid configurations. This underscores the
importance of considering both topology and base material selection during TPMS design. The
study demonstrates the increasing prominence of inertial forces as deformation rates rise,
impacting structural response and failure likelihood in TPMS structures.
These insights inform the design of optimized cellular metamaterials for high-performance
applications requiring superior energy absorption and structural integrity under high loading
rates. The research advances material characterization techniques and computational
modelling capabilities, contributing to the development of next-generation cellular
metamaterials for broader engineering applications.
Ključne besede: Triply Periodic Minimal Surfaces, TPMS, Cell-size-grading, Impact, High-strainrate, Digital Image Correlation
Objavljeno v DKUM: 17.10.2024; Ogledov: 0; Prenosov: 19
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2. Hygiene of medical devices and minimum inhibitory concentrations for alcohol-based and QAC disinfectants among isolates from physical therapy departmentsUrška Rozman, Darja Duh, Mojca Cimerman, Sonja Šostar-Turk, 2022, izvirni znanstveni članek Opis: Disinfectants are used intensively to control and prevent healthcare-associated infections. With continuous use and exposure to disinfectants, bacteria may develop reduced susceptibility. The study aimed to check the hygiene of devices in the physiotherapy department. For isolated bacterial strains, we aimed to determine the minimum inhibitory concentration of five different disinfectant wipe products currently in use. Microbiological environmental sampling in four various institutions in four different cities from two counties was performed, followed by CFU calculation and identification using matrix-assisted laser desorption and ionization with time-of-flight analyzer mass spectrometry (MALDI-TOF). The sampling was performed on three different occasions: before patient use, after patient use, and after disinfection. The susceptibility of isolates to three different alcohol-based and three different quaternary ammonium compounds (QAC) disinfectant wipes was examined by determining the minimal inhibitory concentrations (MIC). We identified 27 different bacterial species from 11 different genera. Gram-positive bacteria predominated. The most abundant genera were Staphylococcus, Micrococcus, and Bacillus. The average MIC values of alcohol-based disinfectants range between 66.61 and 148.82 g/L, and those of QAC-based disinfectants range between 2.4 and 3.5 mg/L. Distinctive strains with four-fold increases in MIC values, compared to average values, were identified. The widespread use of disinfectants can induce a reduction in the susceptibility of bacteria against disinfectants and affect the increase in the proportion of antibiotic-resistant bacteria. Therefore, it is urgent to define clear criteria for defining a microorganism as resistant to disinfectants by setting epidemiological cut-off (ECOFF) values and standardizing protocols for testing the resistance of microorganisms against disinfectants.
Ključne besede: surfaces hygiene, disinfectants, MIC, healthcare institution
Objavljeno v DKUM: 03.07.2024; Ogledov: 106; Prenosov: 14
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3. Sustainability-oriented surface modification of polyester knitted fabrics with chitosanTanja Pušić, Tea Bušac, Kristina Šimić, Mirjana Čurlin, Ana Šaravanja, Katia Grgić, Julija Volmajer Valh, 2024, izvirni znanstveni članek Opis: The existing research deals with the process of modifying polyester knitted fabrics and polyester/cotton knitted fabrics with chitosan and the stability of functionalized surface with chitosan in the washing process according to a standard and an innovative washing procedure. The current research concept aims to evaluate the degree of progressivity and progressiveness: the modification of polyester knitted fabrics with chitosan and an innovative washing process. The polyester and polyester/cotton fabrics modified with chitosan were characterized by a staining test, microscopic analysis, zeta potential measurement, and pilling tendency of the knitted fabrics before and after five and ten washing cycles with reference detergent ECE A. The results of the zeta potential measurement of knitted fabrics functionalized with chitosan confirmed cationization of the polyester and polyester/cotton fabric with chitosan. The presence of chitosan on the washed knitted fabrics in reduced quantities is demonstrated by the staining test, the colour strength (K/S), and the zeta potential values. The staining test and surface charge of the tested knitted fabrics confirmed the research hypothesis regarding the degree of progressivity of the modification of polyester and polyester/cotton knitted fabrics with chitosan and the sustainability of the innovative washing process. The streaming potential proved to be a favorable method for monitoring the stability of chitosan in the washing process in combination with a staining test with the selected dye Remazol Red RB.
Ključne besede: knitted fabrics, polyester, polyester/cotton, chitosan, washing, surfaces
Objavljeno v DKUM: 05.02.2024; Ogledov: 285; Prenosov: 22
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4. Intelligent system for prediction of mechanical properties of material based on metallographic imagesMatej Paulič, David Močnik, Mirko Ficko, Jože Balič, Tomaž Irgolič, Simon Klančnik, 2015, izvirni znanstveni članek Opis: This article presents developed intelligent system for prediction of mechanical properties of material based on metallographic images. The system is composed of two modules. The first module of the system is an algorithm for features extraction from metallographic images. The first algorithm reads metallographic image, which was obtained by microscope, followed by image features extraction with developed algorithm and in the end algorithm calculates proportions of the material microstructure. In this research we need to determine proportions of graphite, ferrite and ausferrite from metallographic images as accurately as possible. The second module of the developed system is a system for prediction of mechanical properties of material. Prediction of mechanical properties of material was performed by feed-forward artificial neural network. As inputs into artificial neural network calculated proportions of graphite, ferrite and ausferrite were used, as targets for training mechanical properties of material were used. Training of artificial neural network was performed on quite small database, but with parameters changing we succeeded. Artificial neural network learned to such extent that the error was acceptable. With the oriented neural network we successfully predicted mechanical properties for excluded sample.
Ključne besede: artificial neural network, factor of phase coherence between the surfaces, fracture toughness, image processing, mechanical properties, metallographic image, ultimate tensile strength, yield strength
Objavljeno v DKUM: 12.07.2017; Ogledov: 1554; Prenosov: 435
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5. Hospital textiles, are they a possible vehicle for healthcare-associated infections?Sabina Fijan, Sonja Šostar-Turk, 2012, pregledni znanstveni članek Opis: Textiles are a common material in healthcare facilities; therefore it is important that they do not pose as a vehicle for the transfer of pathogens to patients or hospital workers. During the course of use hospital textiles become contaminated and laundering is necessary. Laundering of healthcare textiles is most commonly adequate, but in some instances, due to inappropriate disinfection or subsequent recontamination, the textiles may become a contaminated inanimate surface with the possibility to transfer pathogens. In this review we searched the published literature in order to answer four review questions: (1) Are there any reports on the survival of microorganisms on hospital textiles after laundering? (2) Are there any reports that indicate the presence of microorganisms on hospital textiles during use? (3) Are there any reports that microorganisms on textiles are a possible source infection of patients? (4) Are there any reports that microorganisms on textiles are a possible source infection for healthcare workers?
Ključne besede: textile hygiene, disinfection, hospital-acquired infections, inanimate surfaces, infection transmission vehicles
Objavljeno v DKUM: 21.06.2017; Ogledov: 1627; Prenosov: 402
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6. Symmetry preserving algorithm for large displacement frictionless contact by the pre-discretization penalty methodDušan Gabriel, Jiři Plešek, Miran Ulbin, 2004, izvirni znanstveni članek Opis: A three-dimensional contact algorithm based on the pre-discretization penalty method is presented. Using the pre-discretization formulation gives rise to contact searching performed at the surface Gaussian integration points. It is shown that the proposed method is consistent with the continuum formulation ofthe problem and allows an easy incorporation of higher-order elements with midside nodes to the analysis. Moreover, a symmetric treatment of mutually contacting surfaces is preserved even under large displacement increments. Theproposed algorithm utilizes the BFGS method modified for constrained non-linear systems. The effectiveness of quadratic isoparametric elements in contact analysis is tested in terms of numerical examples verified by analytical solutions and experimental measurements. The symmetry of the algorithm is clearly manifested in the problem of impact of two elastic cylinders.
Ključne besede: mechanics, numerical methods, contacting surfaces, contact problems, 3D contact algorithm, discretization, higher order elements, finite element method, Gauss point search, pre-discretization penalty method
Objavljeno v DKUM: 01.06.2012; Ogledov: 2552; Prenosov: 89
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7. Electrokinetic properties of nanocomposite fibresMajda Sfiligoj-Smole, Silvo Hribernik, Nika Veronovski, Manja Kurečič, Karin Stana-Kleinschek, 2011, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Ključne besede: nanocomposite fibres, nanofibres, polymer nanofibres, nanofilled fibres, nanocoated fibres, electrically charged surfaces, zeta potential, elektrokinetic properties
Objavljeno v DKUM: 01.06.2012; Ogledov: 2106; Prenosov: 86
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