Search the digital library catalog

Abstract: We present a novel data-driven surrogate approach for fast evaluation of the deformation dynamics of soft particles, both initially spherical and ellipsoidal, suspended in external flows, specifically predicting the hydrodynamic tractions on the particle surface. The core of the approach relies on expressing the required force dyad as a linear combination of velocity gradient components, modulated by form coefficients. These coefficients scale shear, rotational, and extensional flow contributions to the velocity gradient. Two training strategies are proposed: one utilizing analytical data, which enables a computational speedup, and another based on data obtained with 3D direct numerical simulations (DNS) using the boundary element method (BEM), with the latter demonstrating the feasibility of this approach even in the absence of analytical solutions. Validation against established literature benchmarks confirms the model’s accuracy in three scenarios: (i) ellipsoidal particles in the quasi-rigid limit in pipe flow, (ii) initially spherical particles in shear flow, and (iii) initially ellipsoidal particles in shear flow. In all cases, the data-driven surrogate approach achieves excellent agreement with reference results. This work establishes a foundation for extending our data-driven approach to flow-induced deformations of soft particles of more complex particle shapes, such as superellipsoids and other non-ellipsoidal geometries, where no analytical traction expression is available.
Keywords: neural network, pseudo-rigid bodies, Barycenter and shape dynamics, Lagrangian particle tracking
Published in DKUM: 27.11.2025; Views: 0; Downloads: 2
Full text (7,16 MB)
This document has many files! More...

Abstract: Soft particles in viscous flows are prevalent both in nature and in various industrial applications. Notable examples include biological cells such as blood cells and bacteria as well as hydrogels and vesicles. To model these intriguing particles, we present an extension of our recent, efficient, and versatile pseudo-rigid body approach, originally developed for initially spherical soft particles suspended in arbitrary macroscale viscous flows. The novel extension allows modeling the barycenter and shape dynamics of soft initially non-spherical, i.e. ellipsoidal particles by introducing a novel shape and orientation tensor. We consider soft, micrometer-sized, ellipsoidal particles deforming affinely. To this end, we combine affine deformations (as inherent to a pseudo-rigid body) and the Jeffery-Roscoe model to analytically determine the traction exerted on a soft ellipsoidal particle suspended locally in a creeping flow at the particle scale. Without loss of generality, we assume nonlinear hyperelastic material behavior for the particles considered. The novel extension of our recent numerical approach for soft particles demonstrates that the deformation and motion of the particles can be accurately reproduced also for ellipsoidal particles and captures results from the literature, however, at drastically reduced computational costs. Furthermore, we identify both the tumbling and trembling dynamic regime for soft ellipsoidal particles suspended in simple shear flow again capturing results from the literature. Our extended approach is first validated using experimental and numerical studies from the literature for quasi-rigid as well as soft particles, followed by a comparison of the effects of particle deformability for some well-known fluid flow cases, such as laminar pipe flow, lid-driven cavity flow, and a simplified bifurcation. We find that taking particle deformability into account leads to notable deviations in the particle trajectory compared to rigid particles, with increased deviations for higher initial particle aspect ratio. Furthermore, we demonstrate that our approach can track a statistically relevant number of soft particles in complex flow situations.
Keywords: soft particles, Lagrangian particle tracking, pseudo-rigid bodies, point-particle method
Published in DKUM: 19.05.2025; Views: 0; Downloads: 3
Full text (4,82 MB)
This document has many files! More...

Abstract: Motorcycle riders are an increasing group of road users. The intrinsic characteristics of powered two wheelers (PTW) allow them to be particularly flexible, both in urban and extra-urban environments. Nevertheless, crash statistics indicate that riders involved in road accidents are highly likely to suffer severe injuries, underlining the vulnerability of this group of road users. An element that can greatly affect the safety of PTW users is road design, as roads are usually designed for two-track vehicles (cars, buses, and lorries) and do not consider the needs of PTWs. Additionally, handling a motorcycle is quite different from driving a car; thus, the behaviour of riders is different to that of drivers. The aim of this paper is to compare how different road designs are perceived by riders and drivers and to preliminarily assess if riders’ behaviour and attention allocation are related. For the purpose of this research, an eye-tracking experiment was developed outdoors. Both drivers and riders travelled along a route comprising four different road designs and various road layouts, and the output was analysed both qualitatively and quantitatively. Although it was not possible to carry out a statistical analysis due to the limited number of participants, the results demonstrate that there is a difference in the gaze behaviour of drivers and riders, with the latter being far more focused on the left-hand side of the road and concentrating on defined elements of road design. Furthermore, the experiment demonstrated that a higher number of fixations is related to lower speeds. Finally, it was noted that both kinds of road users focus fairly well on the carriageway, leading to the conclusion that the indications given through road markings may be much more effective than vertical signalisation, which has rarely been observed.
Keywords: road safety, powered two-wheelers (PTW), ridera, eye-tracking, gaze behavior
Published in DKUM: 13.03.2025; Views: 0; Downloads: 7
Full text (3,01 MB)
This document has many files! More...

Abstract: V magistrskem delu smo proučevali interakcije med pešci in avtonomnimi vozili (AV) ter stališča javnosti do sprejemanja avtonomnih vozil. S pomočjo spletne ankete smo analizirali mnenja 108 udeležencev glede varnosti, zanesljivosti in sprejemljivosti AV. Rezultati so pokazali previdnost in zadržanost pri sprejemanju te tehnologije, zlasti glede varnosti ranljivih udeležencev v prometu. Poleg ankete smo izvedli tudi eksperiment sledenja pogledu, kjer smo primerjali odzive pešcev pri prečkanju prehoda pred avtonomnim in navadnim vozilom (NV). Ugotovili smo, da pešci potrebujejo več časa za odločitev o prečkanju prehoda pred avtonomnim vozilom kot pred navadnim vozilom, kar kaže na povečano previdnost in negotovost. Te ugotovitve kažejo na potrebo po izboljšanju varnostnih sistemov in komunikacije med avtonomnimi vozili in pešci.
Keywords: pešci, avtonomna vozila, prometna varnost, eye-tracking, gap acceptance
Published in DKUM: 14.11.2024; Views: 0; Downloads: 45
Full text (6,87 MB)

Abstract: The importance and value of real-world data in healthcare cannot be overstated because it offers a valuable source of insights into patient experiences. Traditional patient-reported experience and outcomes measures (PREMs/PROMs) often fall short in addressing the complexities of these experiences due to subjectivity and their inability to precisely target the questions asked. In contrast, diary recordings offer a promising solution. They can provide a comprehensive picture of psychological well-being, encompassing both psychological and physiological symptoms. This study explores how using advanced digital technologies, i.e., automatic speech recognition and natural language processing, can efficiently capture patient insights in oncology settings. We introduce the MRAST framework, a simplified way to collect, structure, and understand patient data using questionnaires and diary recordings. The framework was validated in a prospective study with 81 colorectal and 85 breast cancer survivors, of whom 37 were male and 129 were female. Overall, the patients evaluated the solution as well made; they found it easy to use and integrate into their daily routine. The majority (75.3%) of the cancer survivors participating in the study were willing to engage in health monitoring activities using digital wearable devices daily for an extended period. Throughout the study, there was a noticeable increase in the number of participants who perceived the system as having excellent usability. Despite some negative feedback, 44.44% of patients still rated the app’s usability as above satisfactory (i.e., 7.9 on 1–10 scale) and the experience with diary recording as above satisfactory (i.e., 7.0 on 1–10 scale). Overall, these findings also underscore the significance of user testing and continuous improvement in enhancing the usability and user acceptance of solutions like the MRAST framework. Overall, the automated extraction of information from diaries represents a pivotal step toward a more patient-centered approach, where healthcare decisions are based on real-world experiences and tailored to individual needs. The potential usefulness of such data is enormous, as it enables better measurement of everyday experiences and opens new avenues for patient-centered care.
Keywords: multilingual framework, risk assessment, symptom tracking, chronic diseases, patient-centered care, real-world data
Published in DKUM: 12.08.2024; Views: 74; Downloads: 34
Full text (5,29 MB)
This document has many files! More...