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Biomechanical comparison of all-polyethylene total knee replacement and its metal-backed equivalent on periprosthetic tibia using the finite element method
(BMC, 2024-02-23) Apostolopoulos, Vasileios; Boháč, Petr; Marcián, Petr; Nachtnebl, Luboš; Mahdal, Michal; Pazourek, Lukáš; Tomáš, Tomáš
BackgroundTotal knee arthroplasty (TKA) with all-polyethylene tibial (APT) components has shown comparable survivorship and clinical outcomes to that with metal-backed tibial (MBT). Although MBT is more frequently implanted, APT equivalents are considered a low-cost variant for elderly patients. A biomechanical analysis was assumed to be suitable to compare the response of the periprosthetic tibia after implantation of TKA NexGen APT and MBT equivalent.MethodsA standardised load model was used representing the highest load achieved during level walking. The geometry and material models were created using computed tomography data. In the analysis, a material model was created that represents a patient with osteopenia.ResultsThe equivalent strain distribution in the models of cancellous bone with an APT component showed values above 1000 mu epsilon in the area below the medial tibial section, with MBT component were primarily localised in the stem tip area. For APT variants, the microstrain values in more than 80% of the volume were in the range from 300 to 1500 mu epsilon, MBT only in less than 64% of the volume.ConclusionThe effect of APT implantation on the periprosthetic tibia was shown as equal or even superior to that of MBT despite maximum strain values occurring in different locations. On the basis of the strain distribution, the state of the bone tissue was analysed to determine whether bone tissue remodelling or remodelling would occur. Following clinical validation, outcomes could eventually modify the implant selection criteria and lead to more frequent implantation of APT components.
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Assessment of URANS-Type Turbulent Flow Modeling of a Single Port Submerged Entry Nozzle (SEN) for Thin Slab Continuous Casting (TSC) Process
(Springer Nature, 2024-02-16) Vakhrushev, Alexander; Karimi-Sibaki, Ebrahim; Wu, Menghuai; Ludwig, Andreas; Nitzl, Gerald; Tang, Yong; Hackl, Gernot; Watzinger, Josef; Boháček, Jan; Kharicha, Abdellah
The numerical methods based on the unsteady Reynolds-averaged Navier–Stokes (URANS) equations are robust tools to model the turbulent flow for the industrial processes. They allow an acceptable grid resolution along with reasonable calculation time. Herein, the URANS approach is validated against a water model experiment for the special single port submerged entry nozzle (SEN) design used in the thin slab casting (TSC) process. A 1-to-2 under-scaled water model was constructed, including the SEN, mold, and strand Plexiglas segments. Paddle-type sensors were instrumented to measure the submeniscus velocity supported by videorecording of the dye injections to provide both qualitative and quantitative verification of the SEN flow simulations. Two advanced URANS-type models (realizable k– and shear stress transport k–) were applied to calculate velocity pattern on meshes with various resolutions. An oscillating single jet flow was detected in the experiment, which the URANS simulations initially struggled to reflect. The dimensionless analysis of the mesh properties and corresponding adjustment of the boundary layers inside the SEN allowed to resolve the flow pattern. The performed fast Fourier transform (FFT) verified a good numerical prediction of the flow frequency spectrum. The corresponding simulation strategy is proposed for the industrial CC process using the URANS approach.
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Multiple normalized solutions for the planar Schrödinger–Poisson system with critical exponential growth
(Springer Nature, 2024-02-16) Chen, Sitong; Radulescu, Vicentiu; Tang, Xianhua
The paper deals with the existence of normalized solutions for the following Schr & ouml;dinger-Poisson system with -constraint: { -Delta u+lambda u+mu(log||& lowast;u2)u=(e(u2-)1-u2)u,x is an element of R-2, integral R(2)u(2)dx=c, where mu>0,lambda is an element of R , will arise as a Lagrange multiplier and the nonlinearity enjoys critical exponential growth of Trudinger-Moser type. By specifying explicit conditions on the energy level c, we detect a geometry of local minimum and a minimax structure for the corresponding energy functional, and prove the existence of two solutions, one being a local minimizer and one of mountain-pass type. In particular, to catch a second solution of mountain-pass type, some sharp estimates of energy levels are proposed, suggesting a new threshold of compactness in the -constraint. Our study extends and complements the results of Cingolani-Jeanjean (SIAM J Math Anal 51(4): 3533-3568, 2019) dealing with the power nonlinearity a|u|p-2uin the case ofa>0andp>4, in the case of and , which seems to be the first contribution in the context of normalized solutions. Our model presents some new difficulties due to the intricate interplay between a logarithmic convolution potential and a nonlinear term of critical exponential type and requires a novel analysis and the implementation of new ideas, especially in the compactness argument. We believe that our approach will open the door to the study of other -constrained problems with critical exponential growth, and the new underlying ideas are of future development and applicability.
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Increasing segmentation performance with synthetic agar plate images
(Elsevier, 2024-02-15) Čičatka, Michal; Burget, Radim; Karásek, Jan; Lancos, Jan
Background: Agar plate analysis is vital for microbiological testing in industries like food, pharmaceuticals, and biotechnology. Manual inspection is slow, laborious, and error -prone, while existing automated systems struggle with the complexity of real -world agar plates. A shortage of diverse datasets hinders the development and evaluation of robust automated systems. Methods: In this paper, two new annotated datasets and a novel methodology for synthetic agar plate generation are presented. The datasets comprise 854 images of cultivated agar plates and 1,588 images of empty agar plates, encompassing various agar plate types and microorganisms. These datasets are an extension of the publicly available BRUKERCOLONY dataset, collectively forming one of the largest publicly available annotated datasets for research. The methodology is based on an efficient image generation pipeline that also simulates cultivation -related phenomena such as haemolysis or chromogenic reactions. Results: The augmentations significantly improved the Dice coefficient of trained U -Net models, increasing it from 0.671 to 0.721. Furthermore, training the U -Net model with a combination of real and 150% synthetic data demonstrated its efficacy, yielding a remarkable Dice coefficient of 0.729, a substantial improvement from the baseline of 0.518. UNet3+ exhibited the highest performance among the U -Net and Attention U -Net architectures, achieving a Dice coefficient of 0.767. Conclusions: Our experiments showed the methodology's applicability to real -world scenarios, even with highly variable agar plates. Our paper contributes to automating agar plate analysis by presenting a new dataset and effective methodology, potentially enhancing fully automated microbiological testing
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Effect of pressing pressure on the capacity of recycled graphite anode
(SPRINGER WIEN, 2024-02-20) Báňa, Jiří; Čudek, Pavel; Šedina, Martin; Šimek, Antonín; Kazda, Tomáš
Due to the increasing demand for lithium-ion batteries, there is an urgent requirement for environmentally friendly and efficient means of recycling these batteries. Graphite, a readily available and cost-effective material, tends to be neglected compared to more expensive metals such as cobalt or nickel. To achieve the new European targets, it will be necessary to focus on recycling even less valuable materials, such as graphite. Direct recycling of graphite represents an environmentally and economically viable solution. However, the capacity of recycled graphite depends on several factors, with pressing pressure being a potential variable. Within this article, we have focused on the impact of pressing pressure of spent graphite anode. The recycling was performed on the battery sample with a known lifetime history. It was found that when optimized, it is possible to achieve high stability and high capacities exceeding 300 mAh/g.