bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of the Shizuoka Hip Fracture Prognostic Score (SHiPS) to Predict Long‐Term Mortality in Patients With Hip Fracture in Japan: A Cohort Study Using the Shizuoka Kokuho Database
Authors: Ohata Emi , Nakatani Eiji , Kaneda Hideaki , Fujimoto Yoh , Tanaka Kiyoshi , Takagi Akira
Published: March 2023

Hip fractures are common in patients of advanced age and are associated with excess mortality. Rapid and accurate prediction of the prognosis using information that can be easily obtained before surgery would be advantageous to clinical management. We performed a population‐based retrospective cohort study using an 8.5‐year Japanese claims database (April 2012–September 2020) to develop and validate a predictive model for long‐term mortality after hip fracture. The study included 43,529 patients (34,499 [79.3%] women) aged ≥65 years with first‐onset hip fracture. During the observation period, 43% of the patients died. Cox regression analysis identified the following prognostic predictors: sex, age, fracture site, nursing care certification, and several comorbidities (any malignancy, renal disease, congestive heart failure, chronic pulmonary disease, liver disease, metastatic solid tumor, and deficiency anemia). We then developed a scoring system called the Shizuoka Hip Fracture Prognostic Score (SHiPS); this system was established by scoring based on each hazard ratio and classifying the degree of mortality risk into four categories based on decision tree analysis. The area under the receiver operating characteristic (ROC) curve (AUC) (95% confidence interval [CI]) of 1‐year, 3‐year, and 5‐year mortality based on the SHiPS was 0.718 (95% CI, 0.706–0.729), 0.736 (95% CI, 0.728–0.745), and 0.758 (95% CI, 0.747–0.769), respectively, indicating good predictive performance of the SHiPS for as long as 5 years after fracture onset. Even when the SHiPS was individually applied to patients with or without surgery after fracture, the prediction performance by the AUC was >0.7. These results indicate that the SHiPS can predict long‐term mortality using preoperative information regardless of whether surgery is performed after hip fracture.
Autonomic dysregulation and self‐injurious thoughts and behaviours in children and young people: A systematic review and meta‐analysis
Authors: Bellato Alessio , Admani Muskaan Aleeza , Deak Camila , Farhat Luis Carlos , Fontana Antunes de Oliveira Maria Carolina , Vasconcelos Rebeca , Malanchini Margherita , Shephard Elizabeth , Michelini Giorgia
Published: March 2023

Background

Self‐injurious thoughts and behaviours (SITBs) have been associated with dysfunction of the Autonomic Nervous System (ANS) in children and young people, suggesting that objective ANS measures may aid assessment of suicide risk, but a systematic synthesis of this literature is currently lacking.

Methods

Following a pre‐registered protocol (PROSPERO CRD42022327605), we conducted a systematic search of PubMed, Medline, Embase, PsycINFO, and Web of Science, for empirical studies published until 10th May 2022 that compared indices of ANS functioning in individuals aged 0–25 years with versus without SITBs, or reported continuous associations between ANS measures and SITBs. Study quality was assessed with the Newcastle‐Ottawa Scales. Pooled effect sizes (Hedge's g) were estimated with random‐effects meta‐analytic models.

Results

Twenty studies (1979 participants) were included in our systematic review, with 16 included in meta‐analyses. Results suggested that SITBs were associated with altered cardiac indices of arousal (g = −0.328, p < 0.001), which was driven by lower heart rate variability in individuals with SITBs (g = −0.375, p = 0.025). Overall results for electrodermal activity were not significant (g = 0.026, p = 0.857), but subgroup analyses showed increased activity in studies of individuals who engaged specifically in non‐suicidal self‐harm (g = 0.249, p = 0.014) but decreased activity in the remaining studies (g = −0.567, p = 0.004).

Conclusions

Our systematic review and meta‐analysis found evidence of reduced parasympathetic regulation as well as more tentative evidence of altered electrodermal activity in children and young people displaying SITBs. Future longitudinal studies should test the clinical utility of these markers for detecting and monitoring suicide risk.
Geographical variation in cool and warm season responses of earlywood and latewood tree‐ring chronologies in Athrotaxis selaginoides
Authors: Adriaanse‐Tucker Andrew , Allen Kathryn J. , English Nathan B.
Published: March 2023

Our understanding of land‐based cool season temperature variability over the past millennium is limited by the relative lack of annually resolved temperature proxies, especially in the Southern Hemisphere. Here, we develop the first earlywood (EW) and latewood (LW) width chronologies from Australia based on the Tasmanian endemic conifer Athrotaxis selaginoides in the far southeast of Australia. We also develop total ring width (RW), EW and LW chronologies from a new site in the far south. We compare the climate responses of RW, EW and adjusted LW chronologies of three A. selagnoides sites near the southern extent of the species with three sites of the species near the northern extent of the species. RW and EW at the southern sites are strongly and positively related to cool season temperature (July–October), but in the north, RW and EW are more strongly and positively related with summer (December–February) temperatures. Once adjusted for the influence of the same growing season EW, LW in the north is very strongly negatively correlated with January–February temperatures across southeastern Australia. The new southern RW and EW chronologies can be used to extend one of only two annually resolved regional cool season temperature reconstructions in the Southern Hemisphere back a further 180 years.
Association of Diet Patterns and Post‐Operative Tympanostomy Tube Otorrhea: A Pilot Study
Authors: Dedhia Kavita , Li Yun , Stallings Virginia A. , Germiller John , Giordano Terri , Dailey Julia , Kong Maria , Durkin Alexandra , Legg‐Jack Ibikari , Nessen Sarah , Schapira Marilyn M.
Published: March 2023

Objective

The objective of this study was to explore diet patterns in children with tympanostomy tube placement (TTP) complicated by postoperative tympanostomy tube otorrhea.

Study Design

Cross‐sectional survey and retrospective cohort study.

Methods

Caregivers of children (0–12 years old), at a tertiary‐care pediatric hospital who underwent TTP within 6 months to 2 years prior to enrollment were included. Children with a history of Down syndrome, cleft palate, craniofacial syndromes, known immunodeficiency, or a non‐English‐speaking family were excluded. Our primary outcome variable was the number of otorrhea episodes. The primary predictor was diet patterns, particularly dessert intake, which was captured through a short food questionnaire.

Results

A total of 286 participants were included in this study. The median age was 1.8 years (IQR, 1.3, 2.9). A total of 174 (61%) participants reported at least one episode of otorrhea. Children who consumed dessert at least two times per week had a higher risk of otorrhea compared to children who consumed one time per week or less (odds ratio [OR], 3.22, 95% Confidence Interval [CI]: 1.69, 6.12). The odds ratio increase continued when considering more stringent criteria for otorrhea (multiple episodes or one episode occurring 4 weeks after surgery), with a 2.33 (95% CI: 1.24, 4.39) higher odds of otorrhea in children with dessert intake at least 2 times per week.

Conclusions

Our pilot data suggest that episodes of otorrhea among children with TTP were associated with more frequent dessert intake. Future studies using prospectively administered diet questionnaires are necessary to confirm these findings.

Level of Evidence

4 Laryngoscope, 133:3575–3581, 2023
Diatomic Metasurface for Efficient Six‐Channel Modulation of Jones Matrix
Authors: Feng Chao , He Tao , Shi Yuzhi , Song Qinghua , Zhu Jingyuan , Zhang Jian , Wang Zhanshan , Tsai Din Ping , Cheng Xinbin
Published: March 2023

Multi‐channel modulation of Jones matrix facilitates encoding a variety of different functions in metasurfaces. However, multiple channels are usually accompanied by a high system complexity and a low efficiency. Here, a compact and effective diatomic metasurface platform that can impose the six‐channel modulation of Jones matrix efficiently is proposed. The metasurface consists of two anisotropic nanopillars with exquisitely designed structural sizes and rotation angles with near‐unity transmission. To verify the methodology, the independent regulation of six Jones‐matrix channels is demonstrated, and three nanoprinting images and three holographic images are integrated into a single metasurface. Furthermore, by interleaving two diatomic meta‐atoms operating at two different wavelengths within a super‐pixel, the multiplexing capacity of the Jones matrix is extended to twelve channels, paving the way to a broader exploitation of multi‐functional optical devices in optical communications, data storage and encryption, and so on.
Single‐cell RNA sequencing reveals distinct immune cell subsets in phalangeal and soft‐tissue recurrence of giant cell tumor of bone
Authors: Yang Meiling , Wang Fen , Liang Huishan , Ji Genxin , Lian Yating , Zou Changye , Zhao Wei
Published: March 2023

Background

Giant cell tumor of the bone (GCTB), an intermediate locally aggressive neoplasm that frequently involves the epiphyseal region of the long bones. GCTB of the distal phalanx and soft‐tissue recurrences are extremely rare. Little is known about the cellular and molecular differences between GCTB of the long bones and rare sites.

Methods

We employed single‐cell RNA sequencing to elucidate the transcriptional profiles of 28,992 cells originating from patients afflicted with GCTB in the femur, distal phalanx, and soft‐tissue relapse. To confirm the critical findings, we subjected the paraffin sections of GCTB to immunohistochemical staining.

Results

Our study revealed that GCTBs in rare sites display distinct immune subtypes and antigen presentation gene signatures. We observed minimal lymphocyte infiltration in GCTBs of the phalanx. Further analyses demonstrated that the transforming growth factor‐β pathway and profibrotic proteins were significantly upregulated in phalanx lesions. In contrast, GCTB cells from soft‐tissue recurrence exhibited discernible chondrocyte characteristics but presented lower antigen‐presenting ability compared to those from femur lesions. Notably, we identified an immunosuppressive subset of mast cells in the soft‐tissue recurrence. The secretion of proangiogenic and immunosuppressive factors from these mast cells suggests their potential role in the formation of vascular‐rich and immunosuppressive niches in recurrent lesions.

Conclusions

Collectively, this study broadens our comprehension of the gene expression patterns observed in infrequent location GCTBs and furnishes a repository of information for illuminating promising therapeutic targets for rare GCTBs.
Alabama, Kansas provider communities looking forward to new CCBHC funding
Authors: Canady Valerie A.
Published: March 2023

Mental Health Weekly last week interviewed two behavioral health care leaders representing Alabama and Kansas, two of 15 states recently awarded $1 million, one‐year Certified Community Behavioral Health Clinic (CCBHC) planning grants, courtesy of the Substance Abuse and Mental Health Services Administration (SAMHSA).
Health care Professionals' experiences of counselling competence in digital care pathways – A descriptive qualitative study
Authors: Kaihlaniemi Juulia , Liljamo Pia , Rajala Mira , Kaakinen Pirjo , Oikarinen Anne
Published: March 2023

Aim

Health care professionals are tasked with the role of supporting patients in using eHealth services in their personal care and counselling competence in digital environments to ensure appropriate patient care. Our aim was to describe health care professionals' experiences of counselling competence in Digital Care Pathways.

Design

A descriptive qualitative study.

Methods

Interviews with semi‐structured questions were conducted. Twelve healthcare professionals were interviewed. The data were analysed using inductive content analysis. The results were reported according to the Consolidated Criteria for Reporting Qualitative Research.

Results

The analysis revealed eight distinct areas of competence related to counselling in Digital Care Pathways, namely, counselling competences related to the use of Digital Care Pathways, supporting patients' self‐care, information technology competence, competence in creating an interactive counselling relationship on the Digital Care Pathway, information management, ethical competence related to counselling in Digital Care Pathways, competence to developing Digital Care Pathways services, and change competence.

No Public or Patient Contribution

Due to the complex and unpredictable circumstances of COVID, people's strict confinement in the hospital prohibited free access to them and the study environment. Therefore, the professionals involved in the study were interviewed through online systems.
Offer cohorts for adult learners by balancing institutional mission and finances
Authors: Sutton Halley
Published: March 2023

CHICAGO — Studies show that adult learners tend to do better in pursuing higher education when they make personal connections with your campus — and with their peers. At George Fox University in Portland, Oregon, cohorts have facilitated successful connections between adult learners and its institution, and helped boost retention and completion rates.
International student mobility in 2023
Authors: Dennis Marguerite J.
Published: March 2023

In May 2022, UNESCO's Institute for Statistics reported that in 2000 just over two million people studied abroad. By 2019 the number had almost tripled to nearly six million. And in September 2022, the IMARC Group published “Higher Education Market: Global Industry Trends, Share Size, Growth, Opportunity and Forecast 2022–2027,” detailing why the higher education market is expected to grow by 20.37% over the next five years.
Chaotic butterfly optimization algorithm based cascaded PI‐TID controller for frequency control in three area hybrid microgrid system
Authors: Bhuyan Mausri , Das Dulal Chandra , Barik Amar Kumar
Published: March 2023

The work represents a unique methodology for control of frequency in three area independent and interconnected hybrid microgrid systems. The proposed hybrid microgrids consist of solar chimney (SC), combined solar gas turbine (CSGT), bio‐diesel operated generator (BDOG), DC link, energy storage units such as battery energy storage unit (BESU), super‐magnetic energy storage unit (SMESU), and redox flow battery (RFB) based. Integration of generating units such as SC, CSGT, BDOG, SMESU, RFB, and DC link in three area hybrid microgrid is also a unique work. A newly developed chaotic butterfly optimization algorithm (CBOA) is applied so as to obtain the optimized standards of the cascaded PI‐TID controller employed with dispatchable generating units. Comparative analysis of different algorithms and controllers is achieved to establish the dominance of the anticipated control strategy. The impact of each component on the system is examined while taking into account various real‐time scenarios. Finally, the efficacy of cascaded PI‐TID controller tuned using CBOA is established by sensitivity analysis with significant changes in source and load circumstances.
Intraoperative Enteral Nutrition Feeding in Free‐Flap Healing after Reconstruction Surgery for Head and Neck Cancers
Authors: Hwang Tzer‐Zen , Wang Yi‐Ming , Jeng Seng‐Feng , Lee Yi‐Chen , Chen Tzu‐Shan , Su Shin‐Ying , Huang Chien‐Chi , Lam Chen‐Fuh
Published: March 2023

Objective

To investigate the beneficial outcomes of intraoperative enteral feeding in free‐flap regeneration after extended head and neck cancer resection and flap reconstruction surgery.

Study Design

A pilot randomized, double‐blind, placebo‐controlled clinical trial.

Setting

Single tertiary care center.

Methods

Patients with advanced head and neck cancers requiring radical tumor resections and free‐flap reconstruction were randomly assigned to receive intraoperative enteral nutrition feeding (100 kcal/100 mL at 10‐20 mL/h) via a nasogastric tube during free‐flap reconstruction (n = 28) or continue fasting (n = 28). The primary outcome was impaired free‐flap regeneration that required surgical reintervention within 90 days after the operation. Participants were enrolled between April 2020 and January 2022; the 90‐day follow‐up ended in April 2022.

Results

The incidence of total or partial flap failure was similar between the 2 groups (14.2% or n = 4 in each group), but the rate of wound dehiscence or edge necrosis was significantly reduced in the feeding group (n = 6 vs 0 for fasting vs feeding; absolute risk reduction, 25.0% [95% confidence interval, 6.9‐43.0]%; p = 0.022). Hospital stay length was shorter (p = 0.042) and hand grip strength was better preserved (p = 0.025) in the feeding group. Plasma concentrations of interleukin (IL)‐6 and IL‐8 after the operation increased significantly more in the fasting group. Perioperative adverse events did not differ between the 2 groups.

Conclusion

Perioperative enteral feeding is a simple, safe, and effective approach to improve perioperative systemic catabolism and proinflammatory reactions, thereby enhancing early wound regeneration after major operations.
Numerical Simulation of Thermo‐electro‐elastic Interactions in Electro‐active Polymers
Authors: Kanan Anas , Kaliske Michael
Published: March 2023

The actuation response of electro‐active polymers (EAP) relies mainly on the coupling between the electric field and the mechanical field. However, the response of polymers can generally be temperature sensitive. Therefore, taking into account the thermal field in addition to the mechanical and the electric fields within a numerical framework may prove necessary to analyze the response of EAP, where temperature changes in the material may influence its behaviour significantly. This contribution presents a coupled thermo‐electro‐mechanical model, where from a numerical point of view direct temperature dependency of the electric and the coupled electro‐mechanical response can be either considered or neglected. Entropic thermo‐electro‐elasticity is adopted. Moreover, a corresponding monolithic and mixed finite element is used to simulate the response of quasi‐incompressible heterogeneous structures under different temperature conditions.
Optimization of Glulam Beams with Spatially Dependent Polymorphic Uncertainty Modeling of Structural Inhomogeneity in Virtual Boards
Authors: Schietzold F. Niklas , Richter Bertram , Graf Wolfgang , Kaliske Michael
Published: March 2023

Several uncertainties are induced by the natural growth of wood. The properties of timber components are affected by naturally varying material characteristics. In addition, structural inhomogeneity has to be accounted for solid wood components. Structural inhomogeneity is dependent on, e.g., natural fissures, inclusions, and especially branches that pervade wooden boards. Those pervasions result in timber boards containing multiple scattered knots.

Polymorphic uncertainty models are required to account for diverse uncertainty characteristics. Natural variability and lack of knowledge are persistent for the uncertainty modeling of natural materials, such as wood. To incorporate those aleatoric and epistemic uncertainty characteristics, uncertainty analyses are performed based on combined fuzzy and stochastic models.

In this contribution, fuzzy probability based random fields are proposed as polymorphic uncertainty approach, with respect to spatial dependencies of the uncertain variables. Methods for the simulation of timber boards are introduced, where knots are established referred to the specific position of the tree trunk axis and spread over the components.

Glulam beams, containing multiple slats of wooden boards, are investigated for bending load cases as numerical example. The tensile zone is simulated with knots in the timber boards. The basic deterministic solution is performed with a local‐orthotropic material formulation, with respect to the grain directions of the wood matrix and knots. Therefore, the knots are discretized separately in the FE mesh. Distinct material properties and grain directions are assigned to the discrete knots and to the surrounding wood matrix, while the grain directions are dependent on the tree trunk axis.

Both, stochastic and fuzzy models are used in field formulations for the spatially dependent polymorphic uncertainties. The knottiness of timber boards – specified by parameters of knot geometry, location and incidence – is dependent on the wood grade. In this contribution, methods for decision making of glulam beam designs are suggested. For this purpose, several design variables are examined. First, the knottiness or wood grade, where a higher grade results in reduced structural inhomogeneity, and second, the thickness of the slats in the glulam beam are considered. Both aspects influence the reliability and robustness of the component, but affect the costs. The maximum endurance of the glulam beam under bending is desired. Therefore, an optimization of the glulam beam design is performed, with respect to the multiple conflicting objectives.
Bifurcation of fiber reinforced inflated membranes with different natural configurations of the constituents
Authors: Topol Heiko , Demirkoparan Hasan , Stoffel Marcus , Markert Bernd , Merodio José
Published: March 2023

This article studies the inflation and bulging of fiber‐reinforced hyperelastic membranes. A neo‐Hookean model describes the mechanical behavior of the ground substance, and a relatively standard reinforcing model describes the mechanical behavior of fibers. The natural configuration of the constituents may differ, for example, because the fiber may be pre‐stretched in comparison to the natural configuration of the ground substance. Additionally, the fibers may be dispersed. Both the pre‐stretch and dispersion of the fibers have an effect on the formation of a bulge. The results explore how material stiffness ratios and fiber arrangements are involved in initiating bulging instabilities. The herein presented results may provide a contribution to understanding the formation of aneurysms.
Modeling the Response of NiTi Endodontic Files Subjected to Cyclic Non‐proportional Loading
Authors: Woodworth Lucas A. , Kaliske Michael
Published: March 2023

Nickel‐Titanium (NiTi) endodontic files have emerged as valuable tools for root canal treatment due to their high strength and flexibility. During treatment, the files are rotated in the bent configuration of the root canal, which leads to cyclic non‐proportional loading. With the goal of understanding the mechanical response of NiTi endodontic files and to allow for an enhanced design of these structures, a constitutive model for shape memory alloys is developed. This model incorporates several of the features present in SMAs relevant for the mechanical response of endodontic files including: transformation, reorientation, yield plasticity, functional fatigue, tension‐compression asymmetry and internal loops. The model is implemented in Ansys using a small strain formulation and extended to finite strains using the nonlinear geometry algorithm in Ansys. Validation of the model is performed by simulating a cyclic torsional experiment from the literature using a simplified file geometry. Finally, the model is applied to simulate a simplified file under torsional rotation in a bent configuration. The results illustrate that the endodontic file develops a torsional oscillation during the course of the cyclic loading, which is directly associated with an increase in residual stresses. Furthermore, the torsional oscillation leads to higher values of the martensite volume fraction and stress.
Application of Statistically Similar Representative Volume Elements of Metal Matrix Composites for the Efficient Simulation of Crack Propagation on the Microscale
Authors: Wingender Dennis , Balzani Daniel
Published: March 2023

The efficiency of various drilling and cutting processes is strongly determined by the wear resistance of the applied tools. For example in mechanized tunnel drilling, metal matrix composites, used as reinforcements on the chisels, are primarily exposed to surface spalling. This wear mechanism is governed by subcritical crack propagation through the material's microstructure, which consists of brittle carbide inclusions surrounded by a ductile matrix. The microstructure morphology strongly influences the crack propagation and thus, the resistance against wear. In order to improve the material's microstructure regarding wear, numerical simulations on the microscale are an important tool to gain knowledge about the influence of the morphology on the crack propagation. The investigated microstructure is given as voxel data obtained from a µCT scan. Because of the high complexity of the microstructure, simulations of crack propagation through it are computationally costly, in particular under cyclic loads. Hence, simplified artificial microstructures are constructed which resemble the morphological as well as mechanical properties of the full microstructure. Here, these less complex microstructures are constructed according to the method in [1,2] for the generation of so‐called Statistically Similar Representative Volume Elements (SSRVE). For the efficient simulation of crack propagation through heterogeneous microstructures based on voxel data, the framework in [10] is applied on the SSRVEs. In numerical simulations, the capability of the SSRVEs to represent the crack behavior of the full microstructure is investigated by comparing with the results are compared to simulations on a cutout of the full microstructure.
Configurational Forces in a Phase Field Model for Fatigue
Authors: Yan Sikang , Schlüter Alexander , Müller Ralf
Published: March 2023

In the last decades, the phase field method has drawn much attention for its application in fracture mechanics because it offers a simple unified framework for crack propagation. The core idea of phase field models for fracture is to introduce a continuous scalar field representing the discontinuous crack. Recently, a phase field model for fatigue has been proposed along this path. The fatigue failure differs from the other fracture scenarios since cracks only occur after a considerable number of load cycles. As fracturing happens, changes of the material microstructure are involved, which causes the evolution of the structural configuration. Thus, a new mathematical description not based on traditional spatial coordinates but the material manifold is desired, which will serve as an elegant analysis tool to understand the energetic forces for crack propagation. Configurational forces are a suitable choice for this purpose, as they describe the energetic driving forces associated with phenomena changing the material itself. In this work, we present a phase field model for fatigue. Furthermore, the phase field fatigue model is analyzed within the concept of configurational forces, which provides a straightforward way to understand the phase field simulations of fatigue fracture.
Structural stress prediction based on deformations using artificial neural networks trained with artificial noise
Authors: Gottardi Nicola , Freitag Steffen , Meschke Günther
Published: March 2023

Artificial Neural Networks (ANN) have found application for multiple problems in structural mechanics and civil engineering. In the new approach developed here, ANNs are used for the determination of the maximum stress resultants in a structure on the basis of monitored displacements. Initially, a simple supported beam subjected up to two vertical forces is considered. The beam is solved analytically for different combinations of load positions and magnitudes defined by Monte‐Carlo sampling. The resulting beam deflections and maximum stress resultants are employed for the training of feedforward neural networks in order to generate metamodels able to predict the maximum bending moment knowing only a few beam input deflections. Subsequently, the concept is applied to a real beam experiment, where a reinforced concrete beam has been tested. It is shown, that the perfect correlation of the beam displacements used as inputs for the ANN training leads to extrapolations when the metamodel is applied to the measured displacements of the real experiment, which are not perfectly correlated. This is source of wrong predictions when the network is applied to these data. The introduction of artificial noise in the synthetic input data in a controlled way before training helps to overcome extrapolation and to increase repeatability and robustness of the metamodels. Various noise levels are applied to the synthetic data to monitor how the ANN performances change over increasing noise and the results along with the limitations of the approach are illustrated.
Modeling the thermomechanical processes and residual stresses in additive manufacturing of metallic components
Authors: Ali Baharin , Heider Yousef , Markert Bernd
Published: March 2023

In additive manufacturing of metallic components and fusion welding, undesirable deformations and residual stresses are common drawbacks, which directly influence the performance and functionality of the manufactured components. In this work, a thermomechanical continuum model is developed by using the phase‐field method to track the evolution of the melting/remelting‐solidification occurring due to the incident of localized heat input sources, e.g, by means of a laser heat source. The result of the thermal analysis is then employed for the mechanical analysis to predict the residual stresses. In the thermal and mechanical analysis, the thermomechanical properties are considered to evolve with the phase‐field variable. In addition, a scalar‐valued history variable is introduced to distinguish between consolidated and loose powder materials. This enables single‐track additive manufacturing simulations with a possible extension to multi‐layer and multi‐track simulations. To verify and validate the modeling approach, the coupled system of equations is implemented in the open‐source FEniCS project and a numerical example for additive manufacturing is solved and compared qualitatively and quantitatively with reference results from the literature.
A surrogate model for the prediction of permeabilities and flow through porous media
Authors: Niekamp Rainer , Niemann Johanna , Schröder Jörg
Published: March 2023

In this contribution we present an approach to generate a data driven surrogate model for the prediction of permeabilities and flow through two dimensional random micro‐heterogeneous materials. The laminar flow is well described by Darcy's law. In order to achieve an efficient computational tool for the generation of the database (up to 103 realizations), needed for the training of the neural networks, we apply a stochastic model based on the Brownian motion. The stationary state of the resulting stochastic model solves the Darcy equation and can be iteratively solved by a Monte Carlo approach applied to a particle simulation. Improved numerical efficiency can be yield by usage of the related transition matrix.
A Penalty Method for Coupling of Finite‐Element and Peridynamic Models
Authors: Pernatii Anna , Gabbert Ulrich , Naumenko Konstantin , Hesse Jan-Timo , Willberg Christian
Published: March 2023

A classical continuum mechanics model no longer fulfills its basic assumptions, when the deformations are not smooth or discontinuous. Peridynamics (PD) as an integral formulation could better overcome these issues. Therefore, it is better suited to solve fracture problems such as crack initiation, its growth and formation of crack patterns. In PD the magnitudes of internal forces at a material point depend on the collective interaction of all material points within a subdomain called horizon. To take advances from the formulation, typically it is implemented in a mesh‐free form. In that case, it is easy to separate interactions between different material points. As consequence, a relatively high resolution is required to describe continuous deformation functions and, consequently computationally expensive. Therefore, the application of mesh‐free PD in undamaged regions requires an unnecessary high effort for receiving sufficient accurate results. In contrast, the finite element method (FEM) as a classical continuum mechanics‐based approach, is very efficient, if continuous stress distributions can be assumed. Consequently, a computational cost reduction can be achieved, if the PD is applied in the local damaged zone only and the remaining area is modeled and analyzed with the classical FEM. Realization of such an approach requires a sufficient accurate coupling of the PD and the FEM subdomains.

A brief overview about different coupling approaches is given. Then the general approach of an Arlequin based method is presented. Here the coupling is achieved via an overlapping of PD and FEM areas. The coupling equations are developed and realized with help of the Penalty method. The Penalty method is considered as an alternative procedure to the Lagrange multiplier strategy without creating new unknowns, which essentially simplifies the coupled PD‐FEM approach. The validity and limits of the proposed technique are demonstrated through analysis, where the choice of the Penalty number is discussed as well as artificial wave oscillations, caused by the coupling area.
Variety of Planar Fourth‐Order Fiber Orientation Tensors and Implications on Effective Elastic Stiffnesses
Authors: Bauer Julian Karl , Seelig Thomas , Hrymak Andrew , Böhlke Thomas
Published: March 2023

In this contribution, selected results from [1–3] are presented in a compact and simplified way. In addition, the variety of fiber orientation tensors is used to determine a maximum deviation of the direction‐dependent Young's modulus, which can arise if only second‐order directional information is included in a specific meanfield homogenization. Focusing on the special case of planar fiber distributions, the variety of fiber orientation tensors identified in [1] is considered as a design space. This design space is completely explored for the orientation‐averaging homogenization following [4], fixed material parameters and fixed fiber volume content. The possible directional dependence of the resulting effective stiffnesses is graphically presented using polar plots of the direction‐dependent Young's modulus. These polar plots are arranged on two‐dimensional slices within the parameter space of planar fourth‐order fiber orientation tensors. This gives a complete representation of the influence of the orientation tensor on the anisotropic stiffness tensor. Consequences of closure approximations, i.e., restriction to second‐order directional information, are demonstrated and motivate measurement of fourth‐order fiber orientation tensors.
Mathematical modeling of electro‐elastic dislocations in piezoelectric materials
Authors: Agiasofitou Eleni , Lazar Markus
Published: March 2023

In this work, based on the theory of linear incompatible piezoelectricity with eigendistortion and eigenelectric field, the concept of electro‐elastic dislocations is presented. Both field variables, the displacement vector u and the electrostatic potential φ, possess a jump discontinuity at the dislocation surface. Electro‐elastic dislocations are described not only by the dislocation density tensor but also by a new introduced field, the so‐called electric dislocation density vector. In addition to electro‐elastic dislocations, inhomogeneities, body forces and body charges are also considered. Within this framework, material balance laws that correspond to the symmetries of translation, scaling and rotation are derived. All fundamental fields of configurational mechanics like the Eshelby stress tensor, the electro‐elastic Peach‐Koehler force, the Cherepanov force, the Eshelby force among others, which take place in the broken (translational, scaling and rotational) conservation laws anymore are given.
Two‐scale FE‐FFT‐based thermo‐mechanically coupled modeling of elasto‐viscoplastic polycrystalline materials at finite strains
Authors: Schmidt Annika , Gierden Christian , Waimann Johanna , Svendsen Bob , Reese Stefanie
Published: March 2023

Due to the general pursuit of technological advancement, structural components need to meet increasingly higher standards. In order to optimize the performance behavior of the used materials, detailed knowledge of the overall as well as microscopic material behavior under certain mechanical and thermal loading conditions is required. Hence, we present a two‐scale finite element (FE) and fast Fourier transformation (FFT)‐based method incorporating finite strains and a thermo‐mechanically coupled constitutive model for elasto‐viscoplastic polycrystalline materials. Assuming that the length scale of the microscale is sufficiently smaller compared to the length scale of the macroscale, we consider the macroscopic and microscopic boundary value problem as two coupled subproblems. The macroscopic boundary value problem is solved utilizing the finite element method. In each macroscopic integration point, the microscopic boundary value problem is embedded as a periodic unit cell whose solution fields are computed utilizing fast Fourier transforms and a Newton‐Krylov solver. The scale transition is performed by defining the macroscopic quantities via the volume averages of their microscopic counterparts. In order to demonstrate the use of the proposed framework, we predict the macroscopic and microscopic fields of a polycrystalline material within a numerical example using an efficient and accurate FE‐FFT‐based two‐scale method.
A comparative study between phase‐field and micromorphic gradient‐extended damage models for brittle fracture
Authors: Harandi Ali , Tabib Majd , Alatassi Baker , Brepols Tim , Rezaei Shahed , Reese Stefanie
Published: March 2023

To circumvent a mesh dependency of damage models, non‐local approaches such as phase‐field and gradient‐extended damage models have shown a good capability and attracted a lot of attention for modeling fracture. These models can predict crack nucleation, kinking, and branching. The gradient‐extended formulation proposed by [1, 2], which includes a micromorphic degree of freedom for damage, is connected to a phase‐field damage model presented in [3]; by connecting fracture parameters in brittle fracture. The latter is followed by comparing the thermodynamic consistency of these models. Despite having similarities in the formulation, gradient‐extended models differ from the standard phase‐field ones by having a damage threshold. Besides that, the local iteration exists in the gradient‐extended damage models. By employing the cohesive phase‐field model or the Angiotensin type 1 (AT1), a damage threshold appears in the formulation; by having a linear term for damage in the crack density function, see [4,5,12]. A comparison between these models is made, by taking several numerical examples and comparing their responses in a quasi‐static case. Moreover, the feasibility of different responses is addressed when one uses a standard Newton‐Raphson solver or the arc‐length one for solving a boundary value problem.
Accurate integration of trimmed cells based on Bezier approximation
Authors: Hosseini Seyed Farhad , Gorji Mahan , Düster Alexander
Published: March 2023

In this work, a new adaptive integration method for simulation of two‐dimensional linear elasticity problems is presented. The main benefit of the proposed method is the reduction of the computational cost by lowering the number of integration points required to reach a certain level of accuracy. The main concept of the proposed method is to calculate new weights for trimmed cells employing the advantage of Bezier parametric curves. Within this concept, it is possible to map a square to a triangle with one curved edge where any curved edge is approximated by a parametric Bezier curve. In this way, a new set of Gaussian quadrature points is introduced for each trimmed cell in a fast and robust way. Besides main mapping cases, the integration method includes supplementary cases as well to increase the robustness and generality of the method. In the next step, the proposed method is implemented in a two‐dimensional fictitious domain code in MATLAB to solve structural problems. The results will be compared to those obtained through the commercial finite element code ABAQUS. It is shown that the proposed method is accurate and robust.
Aspects of accuracy and uniqueness of solutions in data‐driven mechanics
Authors: Bartel Thorsten , Harnisch Marius , Menzel Andreas , Schweizer Ben
Published: March 2023

Data‐driven methods provide great potential for future applications in engineering, for example in terms of more efficient simulations. Conventional material models and the associated constitutive equations are substituted by a minimization of a distance between so‐called material and mechanical states, which, however, leads to non‐unique solutions. The aim of this paper is to analyze the influence of the chosen initial values on the accuracy of the obtained results. Furthermore, Mixed Integer Quadratic Programming (MIQP) is implemented and its applicability to data‐driven mechanics is assessed.
The high cycle fatigue testing of High‐Performance Concretes using high frequency excitation
Authors: Madadi Hamid , Steeb Holger
Published: March 2023

The effect of fatigue failure in brittle materials like (ultra) High Performance Concrete (UHPC) due to cyclic loading causes unexpected failure that consequently results in heavy costs in marine and civil structures. To characterize the effect of fatigue, cyclic loading tests are performed, and “the number of cycles to failure” are experimentally determined. One problem with these kinds of tests is that such experimental investigations are potentially expensive, i.e., time‐consuming process since the number of loading cycles could be extremely high. Further, within the different damage phases of the cycling tests, one has no access to the small‐scale, i.e., microscopical evolution of (micro‐)cracks. Additionally, a full characterization of the small‐strain stiffness evolution of the material is challenging. The goal of the research investigation is to combine a (large amplitude) High Cycle Fatigue experiment with a (low amplitude) Dynamic Mechanical Analysis (DMA). Using a setup based on the piezoelectric actuator, the (rate‐dependent) mechanical properties of the material in tangential space, and the failure modes of the material will be examined accurately. The excitation frequency is between 0.01 Hz to 1000 Hz which allows for reducing the experimental investigation time to failure. Further, it allows investigating the effect of frequency on the number of cycles to failure. Firstly, experimental results for HPC and berea sandstone samples will be presented. Harmonic experimental data include (direct) strain measurements in axial and circumferential directions as well as forces in axial directions. In addition, the resulting complex Young's modulus and evolving damage‐like “history” of HPC and berea sandstone specimens will be shown.
A comparison of different nonlinear shell theories for rotating fluid‐filled structures
Authors: Schmidt Rico , Ams Alfons
Published: March 2023

Rotating fluid‐filled shell structures can be used for different applications in technique. Because of spin‐softening as well as stress‐stiffening it is essential to consider geometrical non‐linearities. Additionally, shear deformation is getting important in case of thick shells. At this point different theories from KIRCHHOFF‐LOVE (no shear deformation) and MINDLIN‐REISSNER (first order shear deformation) are compared with each other.

For both theories the nonlinear kinematics are shown and therewith the HAMILTON's principle is evaluated to receive the equations of motion. The solution of the corresponding eigenvalue problem is done with a global RITZ approach on the one hand, on the other hand with local FE‐discretization. Different results of rotating and non‐rotating cylindrical shells with respect to their eigenfrequencies are presented and compared. Furthermore, experimental data is used for validation.
Hyperelastic material modelling using symbolic regression
Authors: Abdusalamov Rasul , Hillgärtner Markus , Itskov Mikhail
Published: March 2023

Recently, data‐driven approaches in the field of material modeling have gained significant attention. A major advantage of these approaches is the direct integration of experimental results into the models. Nevertheless, artificial neural networks (ANNs) are especially challenging to interpret from a physical point of view, since internal processes of ANNs are difficult to understand.

In this work a new automatic method for the generation of constitutive models for hyperelastic materials is introduced. The presented method is based on symbolic regression, which is a genetic algorithm. Thereby, a mathematical model in the form of an algebraic expression is found that fits the given data as accurately as possible and has a compact representation. The strain energy density function is determined directly as a function of the strain invariants. The proposed ansatz is embedded into a continuum mechanical framework combining the benefits of known physical relations with the unbiased optimization approach of symbolic regression. Benchmark tests for the generalized Mooney‐Rivlin model for uniaxial, equibiaxial and pure shear tests are presented. Finally, the presented procedure is tested on a temperature‐dependent dataset of a thermoplastic polyester elastomer. A good agreement between obtained material models and experimental data is demonstrated.
Molecular Dynamics Study on the Effect of Interfacial Cellullose Polymers in Strengthening the Stress Transfer Between Alumina Nanoparticles and Epoxy
Authors: Al-Maharma Ahmad Y. , Bamer Franz , Markert Bernd
Published: March 2023

Cellulose polymers are widely used to fabricate green composites, implemented as fiber, matrix, and adhesive material between them. In this study, cellulose polymers are used as interphase material between spherical nanoparticles of hydroxylated alumina (Al2O3) and epoxy. Molecular dynamics simulations using the large‐scale atomic/molecular massively parallel simulator (LAMMPS) are utilized to investigate the effect of the cellulose content on the stiffness and tensile strength of epoxy/alumina nanocomposites. Polymer consistent forcefield (PCFF) and its supplement provided by MedeA software (PCFF+) define the interactions between the atoms. The simulation results indicate that incorporating cellulose into epoxy would increase the stiffness and strength properties considering that the cellulose polymers do not experience any agglomeration in the hosting matrix and have good interfacial adhesion with epoxy and alumina. This interfacial adhesion is needed since inserting cellulose polymers between alumina nanoparticles and epoxy would increase the porosity in the interphase region, limiting the stress transfer at the interphase and reducing the tensile strength of epoxy‐alumina nanocomposites.