bluuebunny/crossref_metadata_2025 huggingface dataset:
Upregulation of ENKD1 disrupts cellular homeostasis to promote lymphoma development
Authors: Song Ting , He Na , Hao Ziqian , Yang Yunfan
Published: March 2023

Diffuse large B cell lymphoma (DLBCL) is a common and aggressive form of B cell lymphoma. Approximately 40% of DLBCL patients are incurable despite modern therapeutic approaches. To explore the molecular mechanisms driving the growth and progression of DLBCL, we analyzed genes with differential expression in DLBCL using the Gene Expression Profiling Interactive Analysis database. Enkurin domain‐containing protein 1 (ENKD1), a centrosomal protein‐encoding gene, was found to be highly expressed in DLBCL samples compared with normal samples. The phylogenetic analysis revealed that ENKD1 is evolutionarily conserved. Depletion of ENKD1 in cultured DLBCL cells induced apoptosis, suppressed cell proliferation, and blocked cell cycle progression in the G2/M phase. Moreover, ENKD1 expression positively correlates with the expression levels of a number of cellular homeostatic regulators, including Sperm‐associated antigen 5, a gene encoding an important mitotic regulator. These findings thus demonstrate a critical function for ENKD1 in regulating the cellular homeostasis and suggest a potential value of targeting ENKD1 for the treatment of DLBCL.
Longitudinal changes in subgingival biofilm composition following periodontal treatment
Authors: Johnston William , Rosier Bob T. , Carda‐Diéguez Miguel , Paterson Michael , Watson Paddy , Piela Krystyna , Goulding Marilyn , Ramage Gordon , Baranyia Divyashri , Chen Tsute , Al‐Hebshi Nezar N. , Mira Alex , Culshaw Shauna
Published: March 2023

Background

Current periodontal treatment involves instrumentation using hand and/or ultrasonic instruments, which are used either alone or in combination based on patient and clinician preference, with comparable clinical outcomes. This study sought to investigate early and later changes in the subgingival biofilm following periodontal treatment, to identify whether these changes were associated with treatment outcomes, and to investigate whether the biofilm responded differently to hand compared with ultrasonic instruments.

Methods

This was a secondary‐outcome analysis of a randomized‐controlled trial. Thirty‐eight periodontitis patients received full‐mouth subgingival instrumentation using hand (n = 20) or ultrasonic instrumentation (n = 18). Subgingival plaque was sampled at baseline and 1, 7, and 90 days following treatment. Bacterial DNA was analyzed using 16S rRNA sequencing. Periodontal clinical parameters were evaluated before and after treatment.

Results

Biofilm composition was comparable in both (hand and ultrasonics) treatment groups at all time points (all genera and species; p[adjusted] > 0.05). Large‐scale changes were observed within groups across time points. At days 1 and 7, taxonomic diversity and dysbiosis were reduced, with an increase in health‐associated genera including Streptococcus and Rothia equating to 30% to 40% of the relative abundance. When reassessed at day 90 a subset of samples reformed a microbiome more comparable with baseline, which was independent of instrumentation choice and residual disease.

Conclusions

Hand and ultrasonic instruments induced comparable impacts on the subgingival plaque microbiome. There were marked early changes in the subgingival biofilm composition, although there was limited evidence that community shifts associated with treatment outcomes.
Hospital volume as a predictor of outcomes following pediatric thyroidectomy
Authors: Yu Victor J. , Sasson Daniel Cyrus , Scholfield Daniel , Woods Robbie , Wong Richard , Shaha Ashok , Shah Jatin , Ganly Ian , Lopez Joseph
Published: March 2023

Background

Pediatric thyroidectomy (PT) is an uncommon procedure with a risk of significant morbidity. This study utilizes a national database to identify factors associated with short‐term (30‐day) post‐thyroidectomy complications in children with thyroid cancer.

Methods

The 2016 and 2012 Kids' Inpatient Databases (KID) were used in this study. All children with thyroid cancer undergoing thyroidectomy were included. Complications were categorized into endocrine, nervous, pulmonary, and other. Hospital volume was stratified into high‐volume (performing the top 10% of total cases, HVC) or non‐high‐volume centers (NHVC). Risk factors were analyzed using univariable and multivariable statistical tests.

Results

Six hundred and sixty‐three patients with an average age of 15.93 years met inclusion criteria. Most patients were seen in an NHVC (90.0%) and 37.3% of thyroidectomies were performed with neck dissections. The incidence of any complication was 32.1%. Endocrine complications were the most frequent (32.7%). Independent predictors of any or only endocrine complications were age (odds ratio [OR] = 0.927, p = 0.002, any; OR = 0.926, p = 0.003, endocrine) or concurrent neck dissection (OR = 1.679, p = 0.004, any; OR = 1.683, p = 0.005, endocrine). There was no statistically significant change in odds with hospital volume.

Conclusions

Further investigation into the effect of single surgeon versus hospital volume on the risk of complications in pediatric thyroid cancer surgery is warranted.
Caffeic acid phenethyl ester reverses doxorubicin resistance in breast cancer cells via lipid metabolism regulation at least partly by suppressing the Akt/mTOR/SREBP1 pathway
Authors: Liang Lu‐Chang , Zhao Lei , Yu Bo , Hu Han‐Xiang , He Xu‐Hua , Zhang Yan‐Min
Published: March 2023

Chemotherapy is one of the common treatment methods for breast cancer, but chemoresistance is a severe challenge. Caffeic acid phenethyl ester (CAPE) is an active ingredient of propolis extract and has been shown to have a variety of beneficial effects, and its potential as a treatment for breast cancer is worth exploring. The effects of CAPE on doxorubicin (DOX) resistance were determined by cell counting kit‐8 (CCK‐8) assay, colony‐formation assay, and flow cytometry. Oil Red O staining and the detection of free fatty acids, triglycerides, phospholipids, and cholesterol were performed to assess the status of lipid metabolism. Quantitative polymerase chain reaction (qPCR) and western blotting were applied to investigate the molecules involved in lipid metabolism and the protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/sterol regulatory element binding protein 1 (SREBP1) pathway. CAPE treatment reversed DOX resistance in breast cancer cells and suppressed their lipid metabolism. In addition, CAPE combined with DOX remarkably suppressed SREBP1 expression in part by inhibiting Akt/mTOR pathway activation. Furthermore, by inhibiting lipid metabolism, partly via the Akt/mTOR/SREBP1 pathway, CAPE ultimately reversed DOX resistance in breast cancer. Our results suggest that CAPE treatment reversed DOX resistance in breast cancer cells, at least in part by inhibiting Akt/mTOR/SREBP1 pathway‐mediated lipid metabolism, indicating that CAPE may be an effective substance to assist in the treatment of breast cancer.
Skin‐Inspired Tough Elastomer with Moisture‐Triggered Switchable Mechanical Properties
Authors: Xu Ruoyu , Bai Jing , Zhou Shuai , Shi Zixing
Published: March 2023

Biological tissue usually exhibits good water adaptive mechanical properties, which can maintain high strength and toughness in both wet and dry states. However, synthetic tissue like hydrogel usually becomes hard and brittle in its dry state. Herein, this challenge is met by exploring iron‐catechol complex (TA‐Fe3+) as a great platform combining extremely different polymers (elastomer and hydrogel) to construct new tissue‐like soft composite materials with two different continuous phases, which have not yet been reported. In its dry state, the xerogel phase becomes a reinforced segment to increase the strength of PB without losing its toughness. In its wet state, this soft material becomes high performance hydrogel, where hydrogel phase absorbs high water and elastomer phase can sustain high loading. Such heterogeneous phase structures provide a good idea for designing the soft materials, exhibiting a trade‐off between its high strength and toughness in both wet and dry states. Furthermore, its shape memory behaviors in both its wet and dry state, which shows a great potential application for complex adaptive shape transformation and engineering application like lifting of heavy objects under remote control due to high photo‐thermal transition of TA‐Fe3+ is explored.
Information gain in alternative data: Evidence from e‐commerce sales and analyst earnings forecasts
Authors: Niu Ruiyang , Xie Guanghua , Chen Lin , Zhao Longfeng , Wu Meijun
Published: March 2023

Based on the e‐commerce sales data of A‐share listed firms in China, we explore how e‐commerce sales information affects analyst earnings forecasts. We find that firms' e‐commerce sales information is related to firms' value, increases firms' information transparency, broadens analysts' information channels, and thus improves analyst forecast behavior. Further analysis shows that e‐commerce sales information's positive effect is more significant in firms with high growth ability, low financial information transparency, and without management earnings forecasting. We also find that the positive effect is more salient in the bull market. The findings provide new insights for improving the analyst earnings forecast and offer evidence for the positive significance of e‐commerce sales of alternative data for the capital market in the information era.
A wideband monopolar patch antenna with a high system fidelity factor for IR‐UWB application
Authors: Huang Chaogui , Yang Wei , Chen Bo , Lei Shiwen , Hu Haoquan , Huang Wei
Published: March 2023

A compact, broadband microstrip patch antenna with stable monopole‐like radiation patterns is proposed for impulse‐radio ultrawideband (IR‐UWB) positioning systems. Such the antenna consists of a circular patch with eight conductive vias placed concentrically, resulting in the and modes. Moreover, a tapered feeding probe at its center is presented to enhance the matching and excite an antiresonance mode. The compact size of is obtained by using a square ground. The measured results show that the antenna has an impedance bandwidth of 44.1% from 6 to 9.4 GHz and stable monopole‐like radiation patterns in the frequency domain. Finally, a system fidelity factor larger than 96% and a relatively stable group delay are simulated and measured in the time domain. Therefore, this antenna can be potentially useful for UWB pulse transmission with attractive features in engineering applications.
Circularly polarized edge‐placed printed monopole antenna using theory of characteristic modes
Authors: Ellis Mubarak S. , Owusu‐Achiaw Nana A. , Osei Stephen A. , Nakojah David
Published: March 2023

This article presents a method of using modal analysis to characterize the circular polarization (CP) performance of a printed monopole antenna. The radiator and feedline are positioned on the edge of the substrate and fed accordingly at the edge, and a modified ground plane is employed. The complete antenna without excitation is analyzed using characteristic mode theory to provide physical insight into its CP operation. The modal analysis proves that several nearly orthogonal modes can be generated at certain frequencies with orthogonal phase differences as well. The axial ratio (AR) corresponds to the modal analysis which proves the validity of the modal analysis. An axial ratio bandwidth from 3.1 to 6.2 GHz (66. 7%) is achieved within an S11 bandwidth of 2.6–11 GHz (123.5%). The proposed antenna is compact with stable radiation patterns, easy to design, and fabricate without inserting parasitic patches or inserting slots on the antenna.
Hybrid adiabatic pulse with asymmetry (HAPY): An asymmetric adiabatic pulse with an application in pulsed arterial spin labeling at 7T
Authors: Chi Didi , Blunck Yasmin , Glarin Rebecca , Davey Catherine E. , Zhang Xianyi , Stäb Daniel , Pfeuffer Josef , Johnston Leigh A. , Jin Jin
Published: March 2023

Purpose

A new class of asymmetric adiabatic radiofrequency (RF) pulses, Hybrid Adiabatic Pulse with asYmmetry (HAPY), is designed to be used as the labeling pulse for Pulsed Arterial Spin labeling (PASL) at 7T to reduce overall specific absorption rate (SAR) while maintaining high labeling efficiency with and inhomogeneities.

Methods

Realistic and distributions were extracted from multiple in vivo scans. The proposed class of asymmetric pulses was parameterized and optimized considering these conditions. Simulation and phantoms experiments were performed to compare the optimized pulses with HS‐3, GOIA, and trFOCI pulses. In vivo experiments were conducted to demonstrate the application of HAPY in PICORE PASL at 7T, compared with the GOIA and trFOCI pulses.

Results

HAPYs with different amounts of pulse energy reduction are obtained by the proposed optimization framework. Both simulation and phantom experiments demonstrate that HAPY achieves high labeling efficiency and high selectivity along the critical side despite off‐resonance and low amplitude. In vivo experiments reveal that HAPY is able to generate robust perfusion signal with less overall SAR or shorter pulse repetition time, compared to the GOIA and trFOCI pulses.

Conclusion

The HAPY class of pulses, obtained via systematic optimization tailored to the application of PASL at 7T, reduces power deposition without affecting labeling efficiency, which provides a prospect of further exploiting the benefits of ultra‐high field in ASL.
Assessment of motor unit firing by high‐density surface electromyography detects motor neuronal hyperexcitable state in amyotrophic lateral sclerosis
Authors: Noto Yu‐ichi , Kitaoji Takamasa , Watanabe Kohei , Mizuno Toshiki
Published: March 2023

Introduction/Aims

In amyotrophic lateral sclerosis (ALS), the impact of motor neuron dysfunction on the motor unit (MU) firing pattern remains to be elucidated. The aim of this study was to clarify the characteristics of the MU firing rate and its association with clinical factors in ALS patients using high‐density surface electromyography (HDSEMG) and MU decomposition analysis.

Methods

Nineteen ALS patients and 20 controls prospectively underwent HDSEMG recording of the vastus lateralis muscle during ramp‐up (30% of maximum voluntary contraction) and sustained (10% of maximal voluntary contraction for 60 seconds) contractions on performing isometric knee extension. After decomposition analysis, instantaneous firing rates (IFRs) of individually identified MUs were calculated. Comparison of IFRs and clinical variables between ALS patients and controls and analysis of the correlation between individual mean IFR and clinical variables in ALS patients were performed.

Results

The number of identified MUs was lower in ALS patients than in controls (P = .017). Mean IFRs of MUs (i.e., mean MU firing rates) were higher in ALS patients than in controls at some force levels on ramp‐up contraction (P < .05) and at 50 to 60 seconds during sustained contraction (9.1 [ALS] vs 8.3 [controls] pulses per second; P = .036). There was no correlation between the clinical parameters and mean IFR of each patient.

Discussion

ALS patients had a higher MU firing rate during muscle contraction at a low force level. Noninvasive assessment of the MU firing rate by HDSEMG can detect a motor neuronal hyperexcitable state in ALS patients.
Nurses' knowledge, attitude and behaviour on medical adhesive related skin injury in neonatal department: A survey
Authors: Wu Longyan , Deng Shanshan , Yu Lulu , Rong Hui
Published: March 2023

Aim

To evaluate the status quo of knowledge, attitude and behaviour of neonatal nurses on medical adhesive related skin injury (MARSI).

Design

A survey.

Methods

We conducted a survey on the knowledge, attitude and behaviour of neonatal nurses from September 1–30, 2022. The characteristics, knowledge, attitude and behaviour of neonatal nurses were evaluated and analysed.

Results

A total of 116 neonatal nurses were included. Multivariate regression analysis indicated that had accepted MARSI training, education level, year of work experience are the influencing factors of nurses' MARSI knowledge score (all p < 0.05). Had accepted MARSI training, year of work experience are the influencing factors of nurses' MARSI attitude score (all p < 0.05). Had accepted MARSI training, year of work experience are the influencing factors of nurses' MARSI behaviour score (p = 0.015).

Patient contribution

Neonatal nurses should strengthen their learning and training of MARSI related knowledge, and standardize their protective behaviours to reduce MARSI.
Standardized and validated training to support the charge nurse: Research protocol
Authors: Jubinville Maripier , Longpré Caroline , Tchouaket Nguemeleu Éric
Published: March 2023

Aim

To develop a standardized training for charge nurses.

Design

A developmental research design divided into three parts will be undertaken.

Methods

(1) A scoping review will be used to develop standardized training focusing on charge nurse skills and sub‐skills; (2) a Delphi review with nurses, managers and researchers will validate the content of the training; content validity will be assessed over sufficient rounds of review to obtain a content validity index of over 0.7 and (3) a cross‐sectional study will pilot test the training with 30 charge nurses.

Results

This study will describe the development of updated and empirically validated training to be systematically implemented in healthcare institutions and offered to charge nurses when they begin.
Local Refinement in Isogeometric Analysis of Detailed Tire Models
Authors: Israfilova Alina , Garcia Mario A. , Kaliske Michael
Published: March 2023

Isogeometric Analysis (IGA) and its unconventional basis functions bring undeniable benefits to the numerical analysis of solid bodies with a complex geometrical shape such as pneumatic tires. This approach erases barriers between the stage of design and the computational environment. Preservation of the exact geometrical description of the real body and the nature of functions at hand allow for higher precision of simulations for different physical phenomena.

This contribution is aimed to show further developments in the framework for rolling simulation of tires using IGA. The large support of Non‐Uniform Rational B‐Splines (NURBS) provides continuous variable fields along the contact patch. Truncated hierarchical B‐splines (THB‐splines), implemented into an in‐house Finite Element Analysis (FEA) code, improve the modeling of tires by locally refining the contact zone. Global extraction operators bring the hierarchical concept as close as possible to a standard FEA code structure, flattening the set of nested layers of mesh into a sequence of single‐level elements. Furthermore, an algorithm for the computation of the accelerations at material points based on the relative velocities is adapted. The outlook of this development is the intention to use this algorithm in possible combination with analytical models for the in‐situ estimation of forces and to capture certain mechanical behavior which often are not tracked in experiments or hard and too costly to reproduce.

The sampling procedure within the hierarchically nested basis is elaborated with attention to required adjustments for the nested parent‐child layered analytical meshes created via the introduction of the selective global multilevel extraction operators. Numerical simulations of rolling tires at steady‐state using IGA are presented. The evaluation and comparison of the developed framework are done using uniformly refined and locally refined models in IGA as well as classical FEA models.
Deformation analysis of friction welded hybrid structures
Authors: Heppner Eric , Glüge Rainer , Weber Martin , Woschke Elmar
Published: March 2023

The purpose of this paper is to present a framework for modelling the deformation behaviour of friction welded hybrid structures. The constitutive model is developed for large deformations and nonlinear material behaviour. Moreover, to demonstrate the model's applicabilities, it was implemented into a finite element system (ABAQUS). Subsequently, the simulation results were critically evaluated using experimental data.
A parametric study of high velocity impact prediction using the Mie‐Grüneisen equation
Authors: Kalapis Stephan , Kärtner Moritz , Schröder Kai-Uwe
Published: March 2023

Space debris is a serious threat to space travel. Even small fragments are enough to damage or destroy satellites. To protect against space debris, satellites have protective shields, which come in various forms. These shields must be optimized not only for impact protection but also for secondary factors such as weight and size. New shield systems can be tested experimentally with high‐speed guns. This requires a lot of time, energy, and cost. Here, numerical solvers can be used to evaluate these new shield systems. For example, the smoothed‐particle‐hydrodynamics (SPH) method is commonly used to simulate the large deformations resulting from an impact. Special equations of state are used to capture the effects that occur. One such model is the Mie‐Grüneisen equation of state. It is widely used for this application but does not account for the physical effects that can occur at very high speeds. Other, more complex equations of state can cover these physical effects, but they are often not implemented in commercial numerical solvers such as ABAQUS. Here we show that the Mie‐Grüneisen equation of state can lead to quantitatively reasonable results compared to experimental tests of hypervelocity impacts in ranges up to 10 km/s, even though the physical effects are not covered. A parametric study shows that the Mie‐Grüneisen equation of state can be used to predict plate collapse as a function of impactor diameter and velocity for various target thicknesses. Initial designs of new isotropic protective shields for space debris can thus be numerically tested with low effort and cost.
A magneto‐mechanically coupled material model for magnetic sensor investigation
Authors: Dorn Christian , Wulfinghoff Stephan
Published: March 2023

We consider coupled micro‐magneto‐mechanics with the aim to understand the processes which underpin magnetic noise in composite magnetoelectric sensors. We formulate a material model within the generalized standard material framework. This approach ensures thermodynamic consistency. Using our material model, we study the interaction of domain walls with two types of defects: geometrical defects and eigenstrains. We discuss the interaction and underlying effects in detail.
Towards shape optimization of flow channels in profile extrusion dies using reinforcement learning
Authors: Wolff Daniel , Fricke Clemens , Kemmerling Marco , Elgeti Stefanie
Published: March 2023

Profile extrusion is a continuous production process for manufacturing plastic profiles from molten polymer. Especially interesting is the design of the die, through which the melt is pressed to impart the desired shape. However, due to an inhomogeneous velocity distribution at the die exit or residual stresses inside the extrudate, the final shape of the manufactured part often deviates from the desired one [1]. To avoid these deviations, we want to optimize the shape of the flow channel inside the die computationally. This has already been investigated in the literature using conventional optimization approaches [2,3].

In this work, we investigate the feasibility of Reinforcement Learning (RL) as a learning‐based approach for shape optimization. RL is based on trial‐and‐error interactions of an agent with an environment. For each action, the agent is rewarded and informed about the subsequent state of the environment, which for this application stems from a high‐fidelity Finite Element Method (FEM) simulation.

We will introduce a 2D test case as a proof‐of‐concept, in which an RL agent learns to change the geometry of a flow channel by modifying its representation as computational mesh through a spline‐based deformation method known as Free Form Deformation (FFD) [4]. We will show that an agent can be trained to optimize the geometry for different values of the quantity of interest and that the learning behavior is reproducible, which renders the RL‐based approach promising for further research.
Efficient micromagnetic finite element simulations using a perturbed Lagrange multiplier method
Authors: Reichel Maximilian , Schröder Jörg , Xu Bai-Xiang
Published: March 2023

High performance magnets play an important role in critical issues of modern life such as renewable energy supply, independence of fossile resource and electro mobility. The performance optimization of the established magnetic material system relies mostly on the microstructure control and modification. Here, finite element based in‐silico characterizations, as micromagnetic simulations can be used to predict the magnetization distribution on fine scales. The evolution of the magnetization vectors is described within the framework of the micromagnetic theory by the Landau‐Lifshitz‐Gilbert equation, which requires the numerically challenging preservation of the Euclidean norm of the magnetization vectors. Finite elements have proven to be particularly suitable for an accurate discretization of complex microstructures. However, when introducing the magnetization vectors in terms of a cartesian coordinate system, finite elements do not preserve their unit length a priori. Hence, additional numerical methods have to be considered to fulfill this requirement. This work introduces a perturbed Lagrangian multiplier to penalize all deviations of the magnetization vectors from the Euclidean norm in a suited manner. To reduce the resulting system of equations, an element level based condensation of the Lagrangian multiplier is presented.
On the characterisation of cohesive interfaces by the mode I strain energy release ratio
Authors: Linke Max , Lammering Rolf
Published: March 2023

For the evaluation of the double cantilever beam (DCB) test several approaches are applicable that can provide different results. This ambiguity can significantly affect numerical models which refer to experimentally obtained material parameters. In this work, different approaches for the test evaluation are presented. It is shown that equations derived from the beam theory give reasonable results and good agreement between experiments, numerical and analytical solutions. In this context, DCB tests of glass fibre reinforced polymer substrates with carbon nanotube enriched composites are conducted. A slight negative effect of the latter on the experimental results is found.
An Investigation on Limiting Potentials for Damage Prediction of Viscoelastic Adhesives
Authors: Schumacher Aaron , Matzenmiller Anton
Published: March 2023

In his recent work VOLOKH introduced the energy limiting method as an alternative to continuum damage mechanics developed and envolved by KACHANOV, RABOTNOV, LEMAITRE and many more. In contrast to continuum damage mechanics, the energy limiting method is physically grounded by the process of atomistic debonding and, therefore, motivated on an energy basis. In order to use the energy limiting method within the framework of continuum mechanics, a limiting potential needs to be defined, which can be seen as a macroscopic manifestation of the LENNARD‐JONES bonding potential. The first limiting potential was proposed by VOLOKH and applies an exponential function with one parameter describing the maximum energy that can be absorbed by a material. Consequently, this potential can only capture the onset of damage of different materials, but not the evolution of damage. To overcome this restriction, VOLOKH proposed a generalization applying a Gamma function with two parameters describing the maximum energy and the shape of the damage evolution. Besides this improvement, this generalization has the disadvantages of violating physical plausibility conditions, needing an integration for the evaluation and having coupled parameters, which affect each other. The aim of this contribution is to propose and investigate a collection of analytical limiting potentials satisfying all physical plausibility conditions while having decoupled parameters. Finally, these potentials are used for the damage prediction of thick, viscoelastic adhesives.
Polymorphic Uncertain Structural Analysis: Challenges in Data‐Driven Inelasticity
Authors: Zschocke Selina , Graf Wolfgang , Kaliske Michael
Published: March 2023

This contribution addresses polymorphic uncertainty quantification within structural analysis of reinforced concrete structures composed of heterogeneous concrete and reinforcement (e.g. steel bars or carbon fibres). The macroscopic material behaviour of concrete is strongly dependent on the mesoscopic heterogeneities, which are considered by multiscale modelling. The heterogeneous mesoscopic material behaviour is characterized by representative volume elements (RVE) and the transition of scales is carried out by utilizing numerical homogenization methods.

The concept of data‐driven computational mechanics enables material model free finite element analyses directly based on material data sets, overcoming the necessity of assumptions in material modelling. This approach mainly consists in assigning a stress‐strain state, which leads to a minimum of an objective function and fulfils equilibrium as well as compatibility constraints of every integration point. Inelastic material behaviour is taken into account through the definition of local data sets containing only data set states which are consistent with respect to the past local history . The realistic modelling of structures requires the consideration of data uncertainty. Generalized polymorphic uncertainty models are utilized in order to take variability, imprecision, inaccuracy and incompleteness of material data into account by combining aleatoric and epistemic uncertainty models.

In this contribution, a computationally efficient approach for the consideration of data sets containing uncertain stress‐strain states within data‐driven analysis based on information reduction measurements is presented. Due to generalization, the approach is applicable to various aleatoric, epistemic and polymorphic uncertainty models. The identification of admissible local data sets for taking inelastic material behaviour into account within data‐driven analysis is realized by an energy based history parametrization which is extended to uncertain data. An approach for the efficient selection of these local data sets is presented and challenges in data‐driven inelasticity, particularly in the use case of polymorphic uncertain analyses of concrete structures, are pointed out.
Reliability‐Based Design Optimization of Laser‐Hardened Traces in a Car Front Bumper Under the Influence of Polymorphic Uncertainties
Authors: Miska Niklas , Balzani Daniel
Published: March 2023

In this contribution, the extended Optimal Uncertainty Quantification framework is integrated within the context of reliability‐based design optimizations (RBDO). By that, all advantages the extended Optimal Uncertainty Quantification framework offers for the polymorphic uncertainty quantification, such as the ability to incorporate exact or bounded moment information on epistemic uncertainties without the requirement of the specification of an underlying probability distribution function, can be utilized in order to identify the mathematically sharpest bounds on probabilities as required in an RBDO‐context. The combined framework is tested by means of a numerical example, in which the production and a simple crash scenario of a car front bumper are investigated. Therein, the optimization objective is the maximization of the dissipated energy during the crash, whilst a predefined failure probability is not exceeded.
Simulation Strategy for Fluid‐Structure Interaction of a Pre‐tensioned Dynamic Seal
Authors: Lankenau Tobias , Graf Matthias , Ottink Kathrin , Ebel Thomas
Published: March 2023

After their assembly, dynamic seals operate in a highly deformed and, therefore, pre‐tensioned configuration. The geometrically enforced elastic pre‐stress is essential for the sealing effect, which minimises the fluid passing through the seal gap. When moving, a thin film of the fluid is transported through the seal gap to the opposite side of the seal. The mechanics of this fluid film can be described, for instance, using the Reynolds equation for thin‐film flow. However, the Reynolds equation is limited to the thin gap and can hardly be applied outside; the “thin gap assumption” is avoided here. Additionally, the geometry penetration of the undeformed seal leads to a system that cannot be meshed at the start of a coupled fluid‐structure simulation. We provide a method for solving this type of system using COMSOL Multiphysics. In the first step, solid body contact builds up the elastic pretension. In the following step, the solid body contact is incrementally replaced by fluid pressure induced by an increasing rod movement. The developed model is capable of describing the full loss of solid body contact. It can be applied to simulate local fluid backflow in the vicinity of the seal gap.
New data perspective for selective laser melting simulations
Authors: Luberto Luca , de Payrebrune Kristin M.
Published: March 2023

In selective laser melting (SLM), a powdered material is locally melted by a laser and, after cooling, forms a coherent solid structure that enables the production of complex geometries with various materials. The process involves extreme heating and cooling rates and, thus, large temperature gradients, which lead to anisotropic material properties on the macroscopic scale and, in the worst case, reduced mechanical properties. In order to reliably predict the final mechanical component properties, simulations can be performed at different time and length scales. Enormous computational resources are often required to perform such simulations. In order to transform these simulations into suitable surrogate models, the generated data must be compressed and evaluated in a suitable way. This paper shows first preliminary work and a possible new data description of such simulations.
Stabilization of a Multi‐Dimensional System of Hyperbolic Balance Laws – A Case Study
Authors: Thein Ferdinand
Published: March 2023

In a recent work we studied a stabilization problem for a multi‐dimensional system of n hyperbolic partial differential equations. Using a novel Lyapunov function taking into account the multi‐dimensional geometry we show stabilization in L2 for the arising system using a suitable feedback control. The aim of the present work is to show how this approach can be applied to a particular system. Moreover we present numerical results supporting the theoretical results.
Higher Order Asymptotic Expansion Effects in Laser Cutting Modelling
Authors: Vossen Georg , Itner Dominik
Published: March 2023

A new model for laser cutting is derived by asymptotic expansion techniques. The model describes the movements of the free boundaries of the melt flow and involves higher order expansion terms arising from impulse and energy balance as well as surface tension phenomena. Its stationary solution is derived and analyzed for stability. The stability is correlated to published numerical and experimental results for the cutting quality.
Generative adversarial networks for three‐dimensional microstructure generation
Authors: Henkes Alexander , Wessels Henning
Published: March 2023

Multiscale simulations are demanding in terms of computational resources. In the context of continuum micromechanics, the multiscale problem arises from the need of inferring macroscopic material parameters from the microscale. If the underlying microstructure is explicitly given by means of µCT‐scans, convolutional neural networks can be used to learn the microstructure‐property mapping, which is usually obtained from computational homogenization. The convolutional neural network (CNN) approach provides a significant speedup, especially in the context of heterogeneous or functionally graded materials. Another application is uncertainty quantification, where many expensive evaluations are required. However, one bottleneck of this approach is the large number of training microstructures needed.

This work closes this gap by proposing a generative adversarial network tailored towards three‐dimensional microstructure generation. The lightweight algorithm is able to learn the underlying properties of the material from a single µCT‐scan without the need of explicit descriptors. During prediction time, the network can produce unique three‐dimensional microstructures with the same properties of the original data in a fraction of seconds and at consistently high quality.
A first analysis of possible elementary causes of self‐excited vibrations in roller coaster rides
Authors: Zamora Agustí Marc Guillem , Kecskeméthy Andrés
Published: March 2023

The emergence of vibrations during a roller coaster ride is a recurring phenomenon that can deteriorate the overall experience and accelerate material fatigue. Nevertheless, the causes of such vibrations are still not completely understood and are consequently not fully predictable during the design process. One possible source lies on the irregularities of the rails, acting as a forced external excitation. However, a spectral analysis shows deviations with respect to real measurements [1], as the frequencies are not synchronous with the car velocity divided by the spatial irregularity period. Therefore, there is an indication that the vibrations may be due to self‐excitation and/or that the developed models should consider other phenomena not yet contemplated. This investigation analyses –for the first time to the knowledge of the authors– the plausibility of various causes of self‐excited vibrations during a roller coaster car motion. Given the complex structure of a real roller coaster train and the intricate geometry of the track, the study considers as a first step minimal dynamical models running along a straight track. The cause analyzed in this paper is the contribution of the transversal friction force component that develops in the wheel‐rail contact interface to the destabilization of the longitudinal motion, as well as the effect of the various geometrical and inertial parameters. In this first analysis, no external excitation is considered. For a range of parameters, the minimal system presents a Hopf bifurcation. The results are plausible from the general behavior and thus this cause may be retained as a candidate for the real vibrations occurring in roller coasters. However, the applicability of these preliminary results to general roller coaster motions is not yet confirmed, but a superposition with other causalities may render effective. In further investigations, a complete train motion on curved tracks and external perturbations will be studied to determine the share of the different causes.
A finite strain gradient theory for viscoplasticity by means of micromorphic regularization
Authors: Hamdoun Ayoub , Mahnken Rolf
Published: March 2023

Stretching of polycarbonate films leads to the formation of shear bands in the necking zone [1]. Standard viscoplastic material models render mesh size dependent results, which requires a mathematical regularization. To this end, we present a finite strain gradient theory for a viscoplastic, isotropic material model where we extend the model presented in [2] to a micromorphic model by introducing a new micromorphic variable as an additional degree of freedom with its first gradient [3, 4]. The variable here has the meaning of a micro plastic strain, and is coupled with the macro plastic by a micro penalty term, forcing the macro‐plastic strain to be close to the micro‐plastic strain for the targeted shear band regularization effect. We have implemented the model equations as a three dimensional initial boundary value problem in an in house FE‐tool, to simulate different geometries with different thickness and to compare it the experimental tests. The analysis is performed for a uniaxial tensile geometry as well as for a biaxial tensile geometry. The numerical examples show the ability of the model to regularize the shear bands and solve the problem of localization.
Modelling and simulation of time‐dependent damage and failure within silicone‐based, polymeric adhesives
Authors: Lamm Lukas , Pfeifer Jan Mirco , Holthusen Hagen , Brepols Tim , Reese Stefanie
Published: March 2023

Hyperelastic adhesive joints are used successfully in many areas of industry. Besides all their inherent advantages, materials used for the construction of such bonds show a vast variety of non‐linear effects in their response to mechanical loading, which poses a challenge in modelling and predicting their material response. Recent experiments have shown a strong temporal response when it comes to damage and failure within these materials. This contribution aims to propose a simple but yet flexible formulation to predict time‐dependent damage effects within polymeric adhesives. Besides the main aspects of the thermodynamically consistent development, we also show numerical examples to demonstrate the capabilities of the model.
A Stability Analysis of Modified Patankar–Runge–Kutta methods for a nonlinear Production–Destruction System
Authors: Izgin Thomas , Kopecz Stefan , Meister Andreas
Published: March 2023

Modified Patankar–Runge–Kutta (MPRK) methods preserve the positivity as well as conservativity of a production–destruction system (PDS) of ordinary differential equations for all time step sizes. As a result, higher order MPRK schemes do not belong to the class of general linear methods, i. e. the iterates are generated by a nonlinear map g even when the PDS is linear. Moreover, due to the conservativity of the method, the map g possesses non‐hyperbolic fixed points.

Recently, a new theorem for the investigation of stability properties of non‐hyperbolic fixed points of a nonlinear iteration map was developed. We apply this theorem to understand the stability properties of a family of second order MPRK methods when applied to a nonlinear PDS of ordinary differential equations. It is shown that the fixed points are stable for all time step sizes and members of the MPRK family. Finally, experiments are presented to numerically support the theoretical claims.
Computing tensor operator exponentials within low‐rank tensor formats with application to the parameter‐dependent multigrid method
Authors: Grasedyck Lars , Werthmann Tim A.
Published: March 2023

Uncertainties in physical models can lead to parameter‐dependent linear systems. The representation and solution of these systems are an important task in numerical mathematics. We summarize our previous results on how to represent these systems using low‐rank tensor methods and how to solve these systems using the parameter‐dependent multigrid method. We propose a new approach to compute the tensor operator exponential, by which we mean the matrix exponential applied to a tensor operator, directly within low‐rank tensor formats. This approach is based on classical matrix methods combined with low‐rank arithmetic. The tensor operator exponential within a low‐rank tensor format is used to approximate the inverse diagonal of a low‐rank operator. This approximation is then used as Jacobi smoother for the parameter‐dependent multigrid method. Using this we observe in numerical experiments a grid size independent convergence rate of the multigrid method. Instead of inverting only diagonals of tensor operators, our approach also allows for the inversion of all symmetric positive definite tensor operators.
Topology optimisation of lattice structures to increase damping
Authors: Daniel Christian , Woschke Elmar
Published: March 2023

Lattice structures are lattice‐like assemblies that are inspired by organic systems. The structure inside is made up of cells whose edges form rod‐shaped elements. The size of the cells and the dimensions of the rods can influence the mechanical properties of the entire structure. For the use of lattice structures within engineering applications, stiffness and damping are important parameters. In monolithic designs, the outer contour or the material itself must be modified to change the stiffness and damping. In the case of a lattice structure, moreover, the structure of the inner cells can be adapted, resulting in greater flexibility [1]. Numerical simulations of the structural dynamic behavior will be used to optimize the damping, while heuristic methods are applied to account for the large parameter space. To adjust the simulation model, the damping is measured frequency‐dependent on a real structure which is subsequently used for model adjustment.
Cohesive failure modeling based on the phase‐field approach
Authors: Yin Bo , Zhao Dong , Kaliske Michael
Published: March 2023

Regarding resolving the crack‐induced strong discontinuity problems, e.g., crack faces separating, contact and friction, the recent established approach based on the Representative Crack Element (RCE) framework is developed to describe a robust crack kinematics or crack deformation. The work at hand presents cohesive fracture by elaborating phase‐field modeling within the RCE approach. It constitutes a classical traction‐separation exhibition at the crack faces of the RCE. As such, a phenomenological cohesive adhesion in the RCE can be modeled. In the sequel, the overall material status is interpolated by an intact material state (continuous description) and a fully broken state (RCE description) using the phase‐field degradation function. This allows not only to model a cohesive debonding failure for tensile and shearing deformation, but also to yield an expected contact algorithm when the crack is closing. Furthermore, the unknown crack deformations are solved according to virtual power principle, which provides a consistent framework for the comprehensive constitutive laws of this model.
A path‐independent domain integral to characterize fatigue crack propagation by cyclic material forces
Authors: Khodor Jad , Kaliske Michael
Published: March 2023

A lot of structures undergoing cyclic loading fail at load values smaller than their ultimate design loads. In the framework of fracture mechanics, the crack propagation process can be separated into three different stages. In the first stage, micro‐cracks propagate and form together a macro‐crack. The macro‐crack propagates stably in the second stage, which is also known as the PARIS' regime. In the third stage, the crack propagates unstably leading to the failure of the structure. The pioneering law characterizing the stable crack growth is PARIS' law. The aforementioned law correlates the crack growth rate to the cyclic stress intensity factor. Unfortunately, the cyclic stress intensity factor is limited to cases where the theory of linear elastic fracture mechanics is applicable. To overcome the limitations of the cyclic stress intensity factor, domain‐integrals evaluated by configurational forces or material forces are used as a fatigue crack growth criterion. However, the aforementioned domain‐integrals are path‐dependent. The aim of the study at hand is to derive a path‐independent domain integral to characterize fatigue crack propagation in elastic‐plastic and linear viscoelastic solids at small strains. First of all, the cyclic material forces are derived using the cyclic free energy. Furthermore, the path‐independence of the cyclic material forces approach is illustrated by numerical examples. Finally, the cyclic material force approach is validated by comparing it to experimental results.