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Povzetek: A new branch of the Enhanced Strain Gradient Crystal Plasticity (ESGCP) theory is introduced, based on a quadratic energetic contribution associated with the gradient of the cumulative shear strain on each slip system, within a thermodynamically consistent framework for the formation of slip and kink bands in crystalline microstructures. Together with the recently proposed Nye-tensor-based ESGCP formulation, a new differential operator is developed for the solution of the corresponding nonlocal field equation (or higher-order balance equation). In both branches of the ESGCP theory, the higher-order modulus is intrinsically coupled to the evolving microstructural state of irradiated crystalline lattices during deformation. The ESGCP framework is employed to investigate the Hall–Petch (mean grain size) effect and is systematically compared with classical Strain Gradient Crystal Plasticity (CSGCP) models. The results reveal that, in contrast to CSGCP formulations where the grain-size effect continuously intensifies by the loading, the ESGCP models predict an enhanced grain-size sensitivity at low strain levels followed by a progressive attenuation at higher levels of loading. In addition, a novel quantum computing algorithm based on the quantum Fourier transform (QFT) is developed to solve the classical linear momentum balance equation within a fixed-point iteration scheme, while nonlocal field equations associated with the ESGCP and CSGCP models are addressed using a quantum finite difference approach. It is demonstrated that the proposed QFT-method achieves a poly-logarithmic computational speedup, offering significant advantages for high-resolution simulations of irradiated materials, where both numerical accuracy and computational efficiency are critical for reliable structural integrity assessments in nuclear power plant applications.
Ključne besede: enhanced strain gradient crystal plasticity theory, polycrystalline material, strain localization, shear band, mean-grain size effect
Objavljeno v DiRROS: 05.05.2026; Ogledov: 89; Prenosov: 61
Celotno besedilo (10,20 MB)
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Povzetek: Objective: This study aimed to develop, validate and test the clinical feasibility of ultrasound (US) speckle tracking method based on gradient optical flow for quantifying small longitudinal displacements, shear and strain in peripheral nerves. Methods: The speckle tracking method was validated using seven thawed, fresh-frozen isolated cadaveric forearms. Longitudinal motion of the median nerve was captured using a high-frequency 22 MHz linear probe. An air bubble marker was inserted as a reference point for manual measurement comparison. The precision and accuracy of the method were assessed by comparing manual and automatic measurements. Clinical feasibility was tested on eight healthy subjects, measuring the longitudinal displacement of the median nerve during elbow extension and shoulder anteflexion. Results: The method demonstrated linearity, high precision and accuracy, particularly with a backtrace of five frames, reducing the displacement underestimation to 4%. In cadaveric models, the highest shear strain was observed at the nerve-tissue interfaces. In healthy subjects, the mean displacement of the median nerve was 3.3 ± 1.0 mm, with good inter-rater reliability (intraclass correlation coefficient = 0.87). Conclusion: The US speckle tracking method based on gradient optical flow effectively quantifies small longitudinal displacements and shear strain in peripheral nerves, with high precision and accuracy. However, the method could not detect longitudinal strain in nerves within the range of tested displacements. Future studies should investigate its applicability to smaller and deeper nerves and its usefulness in different pathological conditions.
Ključne besede: gradient optical flow, high-resolution ultrasound, peripheral nerve displacement, shear strain quantification, speckle tracking
Objavljeno v DiRROS: 20.04.2026; Ogledov: 112; Prenosov: 90
Celotno besedilo (2,48 MB)
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Povzetek: Performance-based structural fire design relies on models that capture material and structural behaviour during heating and cooling. Such models require experimental data, but experiments are often time- and resource- intensive. Optimal Experimental Design (OED) can reduce the number of tests needed by minimizing the variance of parameter estimates. This study demonstrates the use of OED, using D-optimality as the optimization criterion, for an experimental setup that measures the thermal elongation of concrete specimens. In these tests, cylindrical concrete specimens are slowly heated to a predefined maximum temperature while their elongation is being measured. The goal of the experimental campaign is to calibrate a model for the free thermal strain of concrete during cooling. The OED determines the optimal exposure that is expected to result in the lowest variance around the mean values of the parameter estimates. The results of the OED are compared with a baseline experimental design without optimization, showing that the advantages of OED become increasingly evident as the number of experimental runs grows and intuitive reasoning becomes less reliable. In addition, the approach is validated considering real experimental data.
Ključne besede: optimal experimental design, concrete, thermal strain, cooling
Objavljeno v DiRROS: 08.04.2026; Ogledov: 129; Prenosov: 34
Celotno besedilo (1,10 MB)
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Povzetek: With the rise of performance-based structural fire design, understanding the behaviour of materials during both the heating and cooling phases of a fire has become essential. Traditionally, research has focused on the heating phase, resulting in limited data on material properties during cooling, in particular for the free thermal strain of concrete. This gap is critical, as free thermal strain significantly influences load redistribution in reinforced concrete structures. Two experimental campaigns were conducted to expand the available data: one using the UGent HIFREP (‘High Intensity Fast-Response Electric Radiant Panel’) and the other employing an electric furnace. The first test campaign provided an extensive dataset on the residual thermal strain, whereas the time- consuming furnace tests provided data for the entire fire event (heating and cooling). These datasets were used to update an existing model through Bayesian inference, coherently integrating the new information. The outcome is a comprehensive probabilistic model that accurately captures the free thermal strain behaviour of concrete throughout both heating and cooling, allowing for a full reliability-based evaluation of concrete structures in fire.
Ključne besede: concrete, cooling, free thermal strain, fire safety, structural fire engineering, experiments, bayesian inference
Objavljeno v DiRROS: 10.03.2026; Ogledov: 245; Prenosov: 46
Celotno besedilo (1,45 MB)
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Povzetek: Magnetoelectric composites integrate the coupling between magnetic and piezoelectric materials to create new functionalities for potential technological applications. This coupling is typically achieved through the exchange of magnetic, electric, or elastic energy across the interfaces between the different constituent materials. Tailoring the strength of the magnetoelectric effect is primarily accomplished by selecting suitable materials for each constituent and by optimizing geometrical and microstructural designs. Various composite architectures, such as (0-3), (2-2), (1-3) and core-shell connectivities, have been studied to enhance magnetoelectric coupling and other required physical properties in composites. This review examines the latest advancements in magnetoelectric materials, focusing on the impact of different interphase connectivity types on their properties and performance. Before exploring magnetic-electric coupling, a brief overview of the historical background of multiferroic magnetoelectric composites is provided. Fundamental concepts underlying the magnetoelectric effect, piezoelectricity, and the magnetostrictive effect are explained, including their origins and examples of these materials' properties. So far, three types of magnetoelectric composite connectivities have been investigated experimentally: particulate composites (0-3), laminated and thin films (2-2), sticks embedded in matrix, core-shell particles, and coaxial fibers.An outlook on the prospects and scientific challenges in the field of multiferroic magnetoelectric composites is given at the end of this review.
Ključne besede: strain-mediated coupling, multiferroic, magnetoelectric, laminated composites, particulate composite, core shell composites
Objavljeno v DiRROS: 19.01.2026; Ogledov: 388; Prenosov: 138
Celotno besedilo (2,82 MB)
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