bluuebunny/crossref_metadata_2025 huggingface dataset:
Race in Rhinology Clinical Trials: A Decade of Disparity
Authors: Spielman Daniel B. , Liebowitz Andi , Kelebeyev Saveliy , Smith Timothy L. , McKinney Kibwei , Woodard Troy , Safi Chetan , Overdevest Jonathan B. , Gudis David A.
Published: January 2021

Objective/Hypothesis

The aim of this study is to assess the ethnic and racial demographics of patients enrolled in prospective chronic rhinosinusitis (CRS) studies relative to the corresponding geographic demographics of the United States (U.S.) census data.

Study Design

Systematic Review and Population analysis.

Methods

A systematic review was performed to identify CRS clinical trials, conducted in the U.S. and published between 2010 and 2020 in which patients were prospectively enrolled. Pooled racial and ethnicity data were compared to national and corresponding regional census data.

Results

Eighty‐three studies were included, comprising 12,027 patients. 50.4% were male and the average age was 49.2 years. 8,810 patients underwent a surgical procedure. Of the 12,027 patients, 81.67% were identified as White, 5.35% as Black, 1.27% as Asian, 0.02% as Pacific Islander, 0.12% as American Indian, and 11.57% were classified as Other. The racial and ethnic composition of the pooled study population differs significantly from the national U.S. census data with the underrepresentation of each minority population (P ≤ .0002). Regional sub‐analyses yield variable results. In the Northeast and West, there was an underrepresentation of all minority populations. In the South and Midwest, Black enrollment was similar to the U.S. census data, while all other minorities were underrepresented.

Conclusions

The racial and ethnic composition of patients enrolled in prospective CRS clinical trials differs significantly from the demographics of the U.S. population. The generalizability and external validity of findings derived from studies comprised of demographically mismatched populations has not been established. Future efforts to enroll more representative populations should be emphasized by the research community, funding bodies, and editorial boards.

Level of Evidence

NA Laryngoscope, 131:1722–1728, 2021
On the tilting‐pad thrust bearings hydrodynamic lubrication under combined numerical and machine learning techniques
Authors: Katsaros Konstantinos P. , Nikolakopoulos Pantelis G.
Published: January 2021

Thrust bearings are machine elements designed to support axial loads in rotating machinery. The hydrodynamic lubrication analysis of such bearings has been a major subject for many studies over the years, leading to important conclusions for design parameters that affect their optimal operating conditions. Furthermore, the last few years, the influence of the industry 4.0 concept has brought new tools that can revolutionise bearings' design. The aim of this study is to combine numerical analysis and machine learning techniques in order to identify optimal thrust bearing's hydrodynamic designs. For this purpose, the Reynolds equations are solved using the finite difference technique on a 2‐D grid of a tilting pivoted bearing's pad. The bearing pressure distribution; load carrying capacity and friction are calculated for multiple operating conditions. The data produced are used as input for the training of regression models that predict the behaviour of the thrust bearing for a wide range of loads and rotating speeds. Simple and multi‐variable, linear, polynomial and SVM regression models are compared for their accuracy to predicting the bearing's operating conditions. The major findings related with three different lubricants, a monograde SAE 30, a multi‐grade SAE 10W40 and a bio‐lubricant AWS 100 that are compared and their optimal operating conditions are suggested in terms of minimum friction force and maximum load carrying capacity for the bearing pad. AWS 100 is found to be the most suitable lubricant that provides the bearing with low operating friction and high load carrying capacity in all studied cases.
High‐Performance Photochromic Hydrogels for Rewritable Information Record
Authors: Long Shijun , Ye Zhihua , Jin Yiqi , Huang Jiacheng , Huang Yiwan , Liao Yonggui , Li Xuefeng
Published: January 2021

Rewritable information record materials usually demand not only reversibly stimuli‐responsive ability, but also strong mechanical properties. To achieve one photochromic hydrogel with super‐strong mechanical strength, hydrophobic molecule spiropyran (SP) has been introduced into a copolymer based on ion‐hybrid crosslink. The hydrogels exhibit both photoinduced reversible color changes and excellent mechanical properties, i.e., the tensile stress of 3.22 MPa, work of tension of 12.8 MJ m−3, and modulus of elasticity of 8.6 MPa. Moreover, the SP‐based Ca2+ crosslinked hydrogels can be enhanced further when exposed to UV‐light via ionic interaction coordination between Ca2+, merocyanine (MC) with polar copolymer chain. In particular, hydrogels have excellent reversible conversion behavior, which can be used to realize repeatable writing of optical information. Thus, the novel design is demonstrated to support future applications in writing repeatable optical information, optical displays, information storage, artificial intelligence systems, and flexible wearable devices.
Do the subsidies help or hurt the remanufacturing closed‐loop supply chain?
Authors: Gong Bengang , Shi Chunming Victor , Li Xiaodong , Cheng Jinshi
Published: January 2021

This study investigates the impacts of the purchasing subsidy (PS) and the dismantling subsidy (DS) on a remanufacturing closed‐loop supply chain with a manufacturer and a dismantling firm. We propose two game models, one with the DS and the other without the DS. We find that an increased PS or DS may be unable to enhance the dismantling firm's efforts. The DS reduces the system profit in contrast to the scenario without the DS. Surprisingly, a simultaneous increase in the two subsidies exacerbates the environmental impacts of remanufacturing closed‐loop supply chain.
A rare gene variation cap +1 (A>C) (HBB: c. −50A>C) associated with codon 5 (‐CT) (HBB: c.17_18delCT) mutation in Syrian family
Authors: Murad Hossam , Moassas Faten , Fakseh Nour A. L.
Published: January 2021

Background

CAP+1 [A>C] (HBB:c.‐50A>C) is a rare silent β‐thalassemia (β‐thal) mutation. Carrier individuals of this mutation show borderline hemoglobin (Hb), mean corpuscular volume (MCV) and Hb A2 levels. This mutation was previously reported in combination with different β‐thalassemia mutations, leading to variable phenotypes.

Case presentation

Here, we describe for the first time the combination of silent CAP+1 [A>C] (HBB:c.‐50A>C) mutation with β0 codon 5 [‐CT] (HBB:c.17_18delCT) mutation in a Syrian proband, leading to beta thalassemia intermedia (TI).

Conclusions

The compound heterozygotes of the silent CAP+1 (A>C) together with another severe beta gene mutation, are phenotypically severe enough to present at an early age and require appropriate therapeutic modalities.
Analysis of Stokes flow of micropolar fluid through a porous cylinder
Authors: Maurya Deepak Kumar , Deo Satya , Khanukaeva D. Yu.
Published: January 2021

The present study concerns the Stokes flow of a micropolar fluid through a porous cylinder whose axis is perpendicular to the plane of the flow. Stream functions, velocities, fluid pressures, and stresses are evaluated for the corresponding fluid flow regions. Streamlines for various values of different parameters are plotted and discussed. Also, the fluid velocity vector and microrotation vector for inside and outside the cylinder are plotted for the different values of the viscosity coefficients and discussed for boundary conditions with continuity of couple stress/continuity of tangential stress. A comparative study of the streamlines, velocity components, and microrotation components is presented for two types of the boundary value problems. In case of boundary value problem with continuity of tangential stress, streamlines have circulatory behavior inside the porous cylinder whereas, streamlines have non‐circulatory nature in case of boundary value problem with continuity of couple stress.
External validation of a model predicting de novo stress urinary incontinence after pelvic organ prolapse surgery
Authors: Yasa Cenk , Gungor Ugurlucan Funda , Dural Ozlem , Yalcın Onay
Published: January 2021

Aims

De novo stress urinary incontinence (SUI) may develop after surgical correction of advanced pelvic organ prolapse (POP) in otherwise continent women. Prediction of which women with POP will develop SUI after the prolapse is corrected is difficult. We aimed to externally validate a previously described prediction model for de novo SUI after performing vaginal surgery for POP and to assess its clinical performance when used as a diagnostic test.

Methods

This retrospective cohort study included all continent women with ≥ stage 2 POP according to the POP‐Quantification System who underwent reconstructive surgery for symptomatic POP. Surgical correction for prolapse of the anterior and/or apical compartment was performed using native tissue or vaginal mesh repair. Seven parameters of the prediction model including age at surgery, number of vaginal births, body mass index, preoperative stress test, previous continence procedure history, urine leakage associated with a feeling of urgency, and diagnosis of diabetes for each patient was provided from the medical records, and the predicted probability of de novo SUI after POP surgery was calculated. The primary outcome used to validate the prediction model was the presence of SUI 1 year after surgery. A receiver operating characteristic (ROC) curve was generated to evaluate the predictive accuracy. A cut‐off point of ≥ 50% was used to evaluate its clinical performance as a diagnostic test.

Results

Two hundred twenty‐five women were suitable for analysis. The rate of de novo SUI was 5.3%. The predictive accuracy of the model in our population using the area under the ROC curve was 0.56 (95% confidence interval = 0.35–0.77). Its performance as a diagnostic test was poor (positive likelihood ratio = 1.20 and negative likelihood ratio = 0.89).

Conclusions

Our clinical validation of this model showed that it did not have good clinical performance. We need future prospective studies to identify and incorporate additional markers of de novo SUI to improve the prediction capacity.
Impairment of accessory nerves around major pelvic ganglion leading to overflow urinary incontinence in rats
Authors: Maeda Kotomi , Hotta Yuji , Shibayama Maaya , Kawata Ryoya , Kataoka Tomoya , Matsumoto Seiji , Yamamoto Tokunori , Kimura Kazunori
Published: January 2021

Aims

To investigate the relationship between lower urinary tract function and the accessory nerve (ACN) arising from the major pelvic ganglion (MPG).

Methods

Ten‐week‐old male Wistar/ST rats were randomly divided into eight groups according to the type of treatment (sham or bilateral accessory nerve injury [BACNI]) and the duration of observation (3 days, 1 week, 2 weeks, or 4 weeks: Sham‐3d, Sham‐1w, Sham‐2w, Sham‐4w, BACNI‐3d, BACNI‐1w, BACNI‐2ws, and BACNI‐4w. BACNI was induced in the following manner: the ACN was crushed for 1 min (2 mm away from the MPG) using reverse‐action tweezers. The same procedure was performed on both sides. On the last day of each observation period, the bladder function was measured by awake cystometry, and histological evaluation was performed.

Results

All rats in the Sham groups micturated normally. In the BACNI‐3d and BACNI‐1w groups, all rats showed symptoms of overflow urinary incontinence (OUI). This OUI improved gradually over time. The bladder's size in the BACNI group was significantly larger than that in the Sham group (p < .01). In addition, fibrosis was observed in the subserosa of the bladder of rats in BACNI groups.

Conclusion

The BACNI model rats exhibited OUI, suggesting that ACN is involved in the lower urinary tract function. It might be possible that ACN controls the function of either the bladder, the urethra, or both.
A robust topology optimization for enlarging working bandwidth of acoustic devices
Authors: Qin Jincheng , Isakari Hiroshi , Taji Kouichi , Takahashi Toru , Matsumoto Toshiro
Published: January 2021

We propose a novel robust topology optimization for designing acoustic devices that are effective for broadband sound waves. Here, we define the objective function as the weighted sum of the acoustic response to an incident wave consisting of a single frequency and its standard deviation (SD) against the frequency perturbation. By approximating the SD, under the assumption that the incident frequency follows the normal distribution, with the high‐order Taylor expansion of the (conventional) objective function, we deal with significant frequency variations. To calculate such an approximation, we need to calculate the high‐order frequency derivatives of the state variable. Here, we define them by integral representations, which enables us to characterize them even when the state variable is defined in an unbounded domain as is often the case with wave scattering problems. We further show that, based on this definition, the high‐order derivatives can efficiently be computed by a combination of the boundary element method and automatic differentiation. We also present a derivation and calculation of the topological derivative for the newly defined objective function. We install all the proposed techniques into a topology optimization method based on the level‐set method to design wideband acoustic devices. The validity and effectiveness of the proposed topology optimization are confirmed through several numerical examples.
Constrained motion design with distinct actuators and motion stabilization
Authors: Sachse Renate , Geiger Florian , Bischoff Manfred
Published: January 2021

The design of adaptive structures is one method to improve sustainability of buildings. Adaptive structures are able to adapt to different loading and environmental conditions or to changing requirements by either small or large shape changes. In the latter case, also the mechanics and properties of the deformation process play a role for the structure's energy efficiency. The method of variational motion design, previously developed in the group of the authors, allows to identify deformation paths between two given geometrical configurations that are optimal with respect to a defined quality function. In a preliminary, academic setting this method assumes that every single degree of freedom is accessible to arbitrary external actuation forces that realize the optimized motion. These (nodal) forces can be recovered a posteriori. The present contribution deals with an extension of the method of motion design by the constraint that the motion is to be realized by a predefined set of actuation forces. These can be either external forces or prescribed length chances of discrete, internal actuator elements. As an additional constraint, static stability of each intermediate configuration during the motion is taken into account. It can be accomplished by enforcing a positive determinant of the stiffness matrix.
Comparative Costs of a Parent‐Only and Parent and Child Treatment for Children with Overweight or Obesity
Authors: Boutelle Kerri N. , Strong David , Liang June , Rhee Kyung E. , Rock Cheryl L. , Wilfley Denise , Epstein Leonard , Crow Scott J.
Published: January 2021

Objective

Models such as family‐based treatment (FBT), delivered to both the parent and child, are considered the most efficacious intervention for children with obesity. However, recent research suggests that parent‐based treatment (PBT; or parent‐only treatment) is noninferior to FBT. The aim of this study was to evaluate the comparative costs of the FBT and PBT models.

Methods

A total of 150 children with overweight and obesity and their parents were randomized to one of two 6‐month treatment programs (FBT or PBT). Data was collected at baseline, during treatment, and following treatment, and and trial‐based analyses of the costs were conducted from a health care sector perspective and a limited societal perspective.

Results

Results suggest that PBT, compared with FBT, had lower costs per parent‐child dyad from the health care sector perspective (PBT = $2,886; FBT = $3,899) and from a limited societal perspective (PBT = $3,231; FBT = $4,279).

Conclusions

These findings suggest that a PBT intervention has lower costs and is noninferior to an FBT intervention for both child and parent weight loss.
Fecal Fungi Dysbiosis in Nonalcoholic Fatty Liver Disease
Authors: You Ningning , Xu Jiali , Wang Liyan , Zhuo Lili , Zhou Jingxin , Song Yu , Ali Aliaweis , Luo Yan , Yang Jin , Yang Wenjun , Zheng Minghua , Xu Jing , Shao Li , Shi Junping
Published: January 2021

Objective

Nonalcoholic fatty liver disease (NAFLD) can systematically harm more aspects of human health than just the liver. In addition to the potential roles of the gut microbiota in NAFLD, commensal fungi can functionally replace intestinal bacteria in maintaining the host immune response in the gut by reversing disease susceptibility. Therefore, gut commensal fungi should be studied to help understand NAFLD.

Methods

The fungal compositions of 79 patients with NAFLD and 34 matched healthy subjects were studied via internal transcribed spacer sequencing. In the NAFLD group, 32 patients underwent liver biopsies to evaluate the associations between gut fungi and NAFLD development.

Results

The fungal microbiota distribution was skewed in the patients with NAFLD. The relative abundances of Talaromyces, Paraphaeosphaeria, Lycoperdon, Curvularia, Phialemoniopsis, Paraboeremia, Sarcinomyces, Cladophialophora, and Sordaria were higher in patients with NAFLD, whereas the abundances of Leptosphaeria, Pseudopithomyces, and Fusicolla were decreased. Patients with NAFLD exhibited more co‐occurring fungal intrakingdom correlations. Several fungi were found to be associated with liver injury, lipid metabolism, and the development of NAFLD.

Conclusions

This study found that gut fungi may play some roles in NAFLD development. Research on gut fungi may be of great value in diagnosing and monitoring NAFLD.
Influence of Nanoparticle Processing on the Thermoelectric Properties of (BixSb1−X)2Te3 Ternary Alloys
Authors: Salloum Sarah , Bendt Georg , Heidelmann Markus , Loza Kateryna , Bayesteh Samaneh , Sepideh Izadi M. , Kawulok Patrick , He Ran , Schlörb Heike , Perez Nicolas , Reith Heiko , Nielsch Kornelius , Schierning Gabi , Schulz Stephan
Published: January 2021

The synthesis of phase‐pure ternary solutions of tetradymite‐type materials (BixSb1−x)2Te3 (x=0.25; 0.50; 0.75) in an ionic liquid approach has been carried out. The nanoparticles are characterized by means of energy‐dispersive X‐ray spectroscopy (EDX), powder X‐ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy. In addition, the role of different processing approaches on the thermoelectric properties ‐ Seebeck coefficient as well as electrical and thermal conductivity ‐ is demonstrated.
Reactivity and Controlled Redox Reactions of Salt‐like Intermetallic Compounds in Imidazolium‐Based Ionic Liquids
Authors: Feng Xian‐Juan , Lerch Swantje , Biller Harry , Micksch Maik , Schmidt Marcus , Baitinger Michael , Strassner Thomas , Grin Yuri , Böhme Bodo
Published: January 2021

Substituted imidazolium ionic liquids (ILs) were investigated for their reactivity towards Na12Ge17 as a model system containing redox‐sensitive Zintl cluster anions. The ILs proved widely inert for imidazolium cations with a 1,2,3‐trisubstitution at least by alkyl groups, and for the anion bis(trifluoromethylsulfonyl)azanide (TFSI). A minute conversion of Na12Ge17 observed on long‐time contact with such ILs was not caused by dissolution of the salt‐like compound, and did thus not provide dissolved Ge clusters. Rather, a cation exchange led to the transfer of Na+ ions into solution. In contrast, by using benzophenone as an oxidizer, heterogeneous redox reactions of Na12Ge17 were initiated, transferring a considerable part of Na+ into solution. At optimized conditions, an X‐ray amorphous product NaGe6.25 was obtained, which was thermally convertible to the crystalline type‐II clathrate Na24–δGe136 with almost completely Na‐filled polyhedral cages, and α‐Ge. The presented method thus provides unexpected access to Na24–δGe136 in bulk quantities.
A Low‐Cost and Scalable Carbon Coated SiO‐Based Anode Material for Lithium‐Ion Batteries
Authors: Huang Zhihao , Dang Guoju , Jiang Wenping , Sun Yuanyu , Yu Meng , Zhang Quansheng , Xie Jingying
Published: January 2021

Silicon monoxide (SiO) is considered as one of the most promising alternative anode materials thanks to its high theoretical capacity, satisfying operating voltage and low cost. However, huge volume change, poor electrical conductivity, and poor cycle performance of SiO dramatically hindered its commercial application. In this work, we report an affordable and simple way for manufacturing carbon‐coated SiO−C composites with good electrochemical performance on kilogram scales. Industrial grade SiO was modified by carbon coating using cheap and environment friendly polyvinyl pyrrolidone (PVP) as carbon source. High‐resolution transmission electron microscopy (HRTEM) and Raman spectra results show that there is an amorphous carbon coating layer with a thickness of about 40 nm on the surface of SiO. The synthesized SiO−C‐650 composite shows great electrochemical performance with a high capacity of 1491 mAh.g−1 at 0.1 C rate and outstanding capacity retention of 67.2 % after 100 cycles. The material also displays an excellent performance with a capacity of 1100 mAh.g−1 at 0.5 C rate. Electrochemical impedance spectroscopy (EIS) results also prove that the carbon coating layer can effectively improve the conductivity of the composite and thus enhance the cycling stability of SiO electrode.
Optimal design of unit‐cell based programmable materials
Authors: Lichti Tobias , Andrä Heiko , Leichner Alexander , Müller Ralf , Wenz Franziska
Published: January 2021

An optimal design for a programmable material based on an array of unit‐cells is established. A programmable material behavior is achieved by using unit‐cells with complex and adjustable features arising from the inner structure of each cell. This type of materials has the potential of replacing the functionality of entire systems consisting of sensors and actuators, provided that an optimal inner structure is given. In this paper the multiscale optimization problem and a solution strategy are presented. An efficient data driven method is used for the solution of the macroscopic boundary value problem. Finally, an example of an optimized parameter distribution for a unit‐cell based material is shown.
Quantized Compressed Sensing by Rectified Linear Units
Authors: Jung Hans Christian , Maly Johannes , Palzer Lars , Stollenwerk Alexander
Published: January 2021

This work is concerned with the problem of recovering high‐dimensional signals, which belong to a convex set of low‐complexity, from a small number of quantized measurements. We propose to estimate the signals via a convex program based on rectified linear units (ReLUs) for two different quantization schemes, namely one‐bit and uniform multi‐bit quantization. Assuming that the linear measurement process can be modelled by a sensing matrix with i.i.d. subgaussian rows, we obtain for both schemes near‐optimal uniform reconstruction guarantees by adding well‐designed noise to the linear measurements prior to the quantization step. In the one‐bit case, we show that the program is robust against adversarial bit corruptions as well as additive noise on the linear measurements. Further, our analysis quantifies precisely how the rate‐distortion relationship of the program changes depending on whether we seek reconstruction accuracies above or below the noise floor. The proofs rely on recent results by Dirksen and Mendelson on non‐Gaussian hyperplane tessellations.
Numerical Analysis for an Electro‐Magneto‐Mechanical Phenomenon with High‐Order Accurate Methods
Authors: Gleim Tobias , Chen Hefeng
Published: January 2021

This paper establishes an axisymmetric model for a levitation device. Therein, the Maxwell equations are combined with the balance of linear momentum. Different possible formulations to describe the MAXWELL equations are presented and compared and discussed in the example. A high order finite element discretization using GALERKIN's method in space and the generalized NEWMARK‐α method in time are developed for the electro‐magneto‐mechanical approach. Several studies on spatial and temporal discretization with respect to convergence will be investigated. In addition, the boundary influences and the domain size with respect to the levitation device are also examined.
A displacement‐based analytical stress solution for various adhesive joint configurations
Authors: Methfessel Thomas S. , Becker Wilfried
Published: January 2021

The present work provides a simple and precise thermo‐mechanical model for the prediction of stress distributions in adhesive joints. A displacement‐based derivation is applied, using a general sandwich‐type model for the overlap region. For the adhesive layer a linear displacement approach is proposed, which captures the variation of the shear stresses in the through‐thickness direction. The model covers various joint configurations with linear‐elastic material behavior under different load cases.
A localized meshless collocation method based on semi‐analytical basis functions for bandgap calculation of elastic waves in phononic crystals
Authors: Fu Zhuo-Jia , Li Lufeng , Gu Yan
Published: January 2021

This paper makes the first attempt to develop an efficient localized meshless collocation method (LMCM) based on the semi‐analytical T‐complete functions to calculate the bandgaps of elastic waves in solid phononic crystals. In comparison with the FEM (COMSOL software), the proposed LMCM can provide the similar accurate results with less computational resources for band structure calculation.
Nonnegative Matrix Factorization models for knowledge extraction from biomedical and other real world data
Authors: Esposito Flavia , Del Buono Nicoletta , Selicato Laura
Published: January 2021

Inspect data for searching valuable information hidden in represents a key aspect in several fields. Fortunately, most of the available data presents an embedded mathematical structure which can be profitably exploited to better investigate latent patterns hidden in them.

Dimensionality Reduction (DR) approaches represent one of the most suitable instrument to untangle latent information. These techniques aim to represent data under analysis onto a low‐dimensional space allowing to consider most of all of intrinsic knowledge as ideal sources (namely basis) of the process under consideration.

In this work we consider Nonnegative Matrix Factorizations (NMFs), which prove to be the most effective among DR approaches in analyzing real‐life nonnegative data.

NMF simulates the human part‐based learning process which states that parts are combined additively to form a whole. Some variants of NMF will be also presented as minimization tasks to which regularization terms can be added in accordance to some additional characteristics (such as sparsity or orthogonality).

We investigate significant computational and interpretative aspects related to NMF according to different application domains, with a specific attention to the analysis of biological data. Moreover we present a new NMF model designed for microarray data analysis that incorporates specific biological proprieties as different constraints. Since NMF and its variants are daily used in several application domains, we conclude stressing how NMF and its constrained variants work in some real life applications, showing some original works related to the analysis of data from engineering field.
Modeling and Simulation of the Thermo‐Mechanically Induced Fracture Behavior of an Epoxy System in Electric Traction Machines
Authors: Böckenhoff Paul , Kästner Markus
Published: January 2021

This papier studies the critical stress state prediction for production‐ and operation‐induced loads on an epoxy‐based mold in an electric rotor. The constitutive behavior of the mold is given by a linear thermo‐viscoelastic material model with an ARRHENIUS‐based time‐temperature superposition, which is modified to also account for chemical curing shrinkage. A finite element analysis (FEA) is performed to evaluate two loading states which result in mold failure due to cracking. The results are compared to experimental evidence. The method is found to predict the location of crack initiation, as well as the direction of crack propagation.
Non‐linear structural membranes and ropes based on Tangential Differential Calculus
Authors: Fries Thomas-Peter , Schöllhammer Daniel
Published: January 2021

The finite strain theory for ropes and membranes is reformulated in the frame of the Tangential Differential Calculus (TDC) resulting in a unification in a geometrical, mechanical, and numerical sense. The resulting formulation applies to parametric and implicit geometry definitions of ropes and membranes. In contrast to classical theories, the formulation is suitable not only to the Surface FEM but also to recent Trace and Cut FEMs.
Reduced order voxel‐based model for computational modelling of highly compressible composite materials
Authors: Iskhakov Tagir , Timothy Jithender J. , Bessa Miguel , Meschke Günther
Published: January 2021

Compressible cementitious materials are used in tunnel lining systems deployed in ground conditions characterised by expansive soils. The deformation capacity of a cementitious material can be enhanced by the introduction of weak inclusions (EPS) and/or pores. The overall behaviour of such porous cementitious composite materials is strongly influenced by the material properties of the individual components (EPS, pores, sand particles, aggregates), the geometry of the constituents, their spatial distribution and volume. The compaction behaviour of such composites can be described by a voxel model with a discrete distribution of material properties, where the voxels are compacted by applying an eigenforce. The proposed model is integrated into the framework of the reduced order self‐consistent clustering strategy at the scale of a Representative Elementary Volume [1]. The accuracy of the reduced order strategy combined with the voxel model is analysed by comparing it to the full voxel compaction model
An Active Female Human Body Model for Simulation of Rear‐End Impact Scenarios
Authors: Kempter Fabian , Kleinbach Christian , Staudenmeyer Martin , Fehr Jörg
Published: January 2021

Whiplash associated disorder (WAD) is a type of injury caused by rear‐end impacts. It is a painful long‐term injury of the soft tissue in the neck, which women suffer from 1.5 to 3 times more often compared to men. Progress in WAD research is difficult, as (i) it occurs at a loading level where muscle activity can no longer be neglected, (ii) as soft tissue characteristics play an essential role in WAD and (iii) there is no consensus on the injury mechanism causing WAD. Therefore, computational models of the human body are the most promising method to advance the understanding of WAD. Here, improvements of boundary and initial conditions are presented together with a discussion of its effects on the head kinematics and neck load.
A simulation of an electric machine considering the coupling of rotor‐ and electrodynamics
Authors: Koch Sebastian , Duvigneau Fabian , Woschke Elmar
Published: January 2021

In this paper, a method is presented to determine the vibrational behavior of an electric motor and the associated structure. Therefore, a holistic simulation approach is used, which takes into account the mutual influence of structural mechanics and electrodynamics. For this purpose, a multi body simulation (MBS) is extended so that electromagnetic loads can be considered, which are calculated by using the finite element method (FEM). In electric machines an undisturbed and constant magnetic field is of great importance. Even small variations of the air gap lead to changes in the magnetic field compared to the ideal geometry, which cause a change in the resulting torque and vibration excitation. Especially local and global asymmetric air gap changes due to load‐ and operation‐dependent deformations of the stator and rotor are problematic. Such deformations result on the one hand from the electromagnetically excited structural vibrations and on the other hand from the rotordynamic loads. For these reasons, it is necessary to consider the electro‐ and structural‐dynamic effects together. The developed method is presented on a simple generic motor to show the influence of the coupling.
The Difference between Optimal Rank‐1 Hankel Approximations in the Frobenius Norm and the Spectral Norm
Authors: Knirsch Hanna , Petz Markus , Plonka Gerlind
Published: January 2021

We present new examples illustrating the fact that optimal Hankel structured rank‐1 approximation of matrices is usually different for the Frobenius and spectral norm. Further, we compare our results for optimal rank‐1 Hankel approximation to the results of the well‐known Cadzow algorithm [3].
Damage modelling for the lifetime prediction of structural adhesive joints subjected to hygro‐thermo‐mechanical long‐term loading
Authors: Kroll Ulrich , Matzenmiller Anton
Published: January 2021

A damage model is presented for the lifetime prediction of structural adhesive joints under hygro‐thermo‐mechanical loading. The damage approach is applied through a cohesive zone model together with the concept of effective stress. It consists of a temperature‐dependent creep and hygro damage evolution due to mechanical loading and chemical aging, caused by the local water concentration. The creep damage part considers multiaxiality of the loading by an equivalent stress. The model parameters are identified by means of rupture times from creep tests under different mechanical loadings, temperatures and humidity conditions. The model and the identified parameters are verified by means of FE‐simulations until rupture of an adhesive joint.
Spatial motion of a pendulum in a jet flow: qualitative aspects and integrability
Authors: Shamolin Maxim V.
Published: January 2021

The presented work is devoted to the problem of motion in a resisting medium of a rigid body whose surface of contact with the medium is only a plane part of its exterior surface. In this case, the force field is constructed from the reasons for the medium action on the body under the streamline (or separation) flow around and quasi‐stationarity conditions. It turns out that studying the motion of such a class of bodies reduces to systems with energy scattering (dissipative systems) or with its pumping (the so‐called anti‐dissipative systems) [1,2]. Note that similar problems were already appeared in applied aerodynamics in the studies of Central Aero‐Hydrodynamic Institute named after professor N. E. Zhukovskii.
Numerical analysis of wave mixing in 3‐D infinite elastic solids with a spherical damage
Authors: Ankay Benjamin , Zhang Chuanzeng
Published: January 2021

In this paper the 3‐D wave propagation in an infinite elastic solid with a spherical damage is numerically simulated by a mapped staggered Chebyshev pseudo‐spectral collocation method. In the numerical simulation process, the so‐called Convolutional‐Perfectly‐Matched‐Layers (CPML) are used to model the absorbing boundaries and the wave excitations are specified inside the corresponding physical domain. Furthermore, to consider different damage models the classical nonlinear elastic and non‐classical hysteretic material laws are used. The main objective of this study is to evaluate the influences of the particular wave modes and the mixing of the incident waves on the generated nonlinear scattered wave field. To analyze the specific scattered wave fields around the spherical damage region the computed time‐domain signals are transformed to the frequency‐domain.
Derivation of Analytical, Closed‐form Formulas for the Calculations of Instantaneous Screw Axes of Arbitrary Rigid 3D Multi‐Body Systems
Authors: Boungard Jonas , Wackerfuß Jens
Published: January 2021

A method to calculate the parameters for each instantaneous and relative instantaneous screw axis in an arbitrary rigid multi‐body system is presented. At first a kinematic analysis is performed which calculates the displacements of all nodes and the rotation of each body. In the next step the displacements of the nodes and the rotation of the bodies are used to calculate the instantaneous screw axis of each body. With the information on the instantaneous screw axes the instantaneous relative screw axes can be computed too. An example of the calculation and the visualization of the instantaneous screw axes is given.
Numerical study of shear bands formation in a 3D‐printed Zr‐based bulk metallic glass under uniaxial loading
Authors: Shi Jianye , Ma Songyun , Markert Bernd
Published: January 2021

Processing metallic materials via selective laser melting (SLM) enables the production of bulk metallic glasses (BMGs) with large size and complex shape, which is difficult or even impossible to achieve using traditional manufacturing techniques. In this study, the initiation and propagation of shear bands as well as the tensile strength in a 3D‐printed BMG with printing defects by means of inherent porosities are studied. A multi‐slips system model based on Mohr‐Coulomb theory is applied.
Machine Learning with Feature Importance Analysis for Tornado Prediction from Environmental Sounding Data
Authors: Coffer Brice , Kubacki Michaela , Wen Yixin , Zhang Ting , Barajas Carlos A. , Gobbert Matthias K.
Published: January 2021

Tornadoes pose a forecast challenge to National Weather Service forecasters because of their quick development and potential for life‐threatening damage. The use of machine learning in severe weather forecasting has recently garnered interest, with current efforts mainly utilizing ground weather radar observations. In this study, we investigate machine learning techniques to discriminate between nontornadic and tornadic storms solely relying on the Rapid Update Cycle (RUC) sounding data that represent the pre‐storm atmospheric conditions. This approach aims to provide for early warnings of tornadic storms, before they form and are detectable by weather radar observations. Feature analysis of a Random Forest machine learning model uncovers that the pressure variable has little impact on the classification process, which is consistent with known key physical attributes of tornado formation, demonstrating the ability of machine learning techniques to provide insight solely based on the data.
Phase field modeling and simulation of the evolution of twelve crystallographic martensite variants in austenitic parent grains
Authors: Graf Marius , Kuntz Matthias , Autenrieth Hermann , Diewald Felix , Müller Ralf
Published: January 2021

Important criteria for the design of dynamically loaded components are strongly influenced by the microstructural properties. Motivated by this, models were developed which can predict the lifetime of components based on the microstructure. With regard to steel materials, the martensitic microstructure is of great importance. The subject of current research is therefore to work on simulation models that can predict the morphology of the microstructure depending on the process parameters during production. In this context a phase‐field model, which considers twelve crystallographic martensite variants corresponding to the Nishiyama‐Wassermann orientation relationship, is presented. The order parameters are used to interpolate between the initial (austenite) and final (martensite) state. With this model, the evolution of a thermal induced martensitic microstructure is simulated. In order to define the displasive characteristics of the martensite variants, the well‐known phenomenological theory of martensite crystallography is deployed. Simulations using the finite element method in the small strain context show the applicability of the model. A qualitative comparison of the simulated microstructures with experimental data is carried out.
On the mechanical modeling of cell components
Authors: Klinge Sandra , Wiegold Tillmann , Aygün Serhat , Gilbert Robert P. , Holzapfel Gerhard A.
Published: January 2021

Eukaryotic cells are complex systems which carry out a variety of different tasks. The current contribution gives insight into the modeling of some of their vital components and represents an overview of results achieved within the international D‐A‐CH project on computational modeling of transport processes in a cell. The first part of the contribution studies viscoelastic effects of cross‐linked actin network embedded in cytosol. The basic‐model is used to simulate the actin behavior at a microscopic level. It considers the influence of the physical length, the end‐to‐end distance and the stretch modulus in order to provide a relationship between the stretch of a single polymer chain and the applied tension force. The effective behavior of the cell cytoplasm is simulated by using the multiscale finite element method. Here, a standard large strain viscous approach is applied for the cytosol, while the generalized Maxwell model simulates viscous effects occurring in filaments due to deviatoric changes. The examples dealing with combinations of tension‐holding tests give insight into the effective behavior of the cytoplasm.

The second part of the talk deals with the viral entry into a cell driven by the receptor motion. In the model developed, the receptor motion is described by the diffusion equation along with two boundary conditions. The first condition represents the balance of fluxes at the front of the contact area. To this end, the velocity is assumed to be proportional to the gradient of the chemical potential. The second condition deals with the energy balance and postulates that the difference in the energy behind and before the front causes the front's movement. The important energy contributions are energy due to the binding of receptors, the free energy of the membrane, the bending energy and the kinetic energy due to the motion of the receptors. The model yields a well‐posed moving boundary problem, which is numerically solved using the finite difference method. The change of receptor density over the membrane as well as the motion of the front of the adhesion zone is studied in the numerical simulations.
Iterative Sparse FFT for M‐sparse Vectors: Deterministic versus Random Sampling
Authors: Plonka Gerlind , von Wulffen Therese
Published: January 2021

In a recent paper [3] we have proposed a deterministic stable sparse FFT algorithm for M‐sparse vectors of length N = 2J with runtime 𝒪(M2 log2N) which generalizes the approach in [2]. Our method is based on a divide‐and‐conquer technique and requires to solve an equation system of Vandermonde type at each iteration step. To ensure numerical stability of the algorithm, the number of rows of the employed Vandermonde matrices at each step has been chosen adaptively in [3]. In this paper, we compare the results of [3] with a random sampling approach for determining the rows of the coefficient matrix.
Parametric Study on Ridges Inducing Secondary Motions in Turbulent Channel Flow
Authors: von Deyn Lars H. , Gatti Davide , Frohnapfel Bettina , Stroh Alexander
Published: January 2021

A DNS parametric study of streamwise‐aligned rectangular ridges is carried out in a fully developed turbulent channel flow with constant flow rate at Reb = 18000. The simulations were carried out systematically varying the ridge height h, width w and structural wavelength S. The ridges generate a strong large‐scale secondary motion, which is measured in terms of the integral swirl strength. Of the presented cases, the configuration with the ridge height h = 0.1 δ, S/w = 4, S = 1 δ produces the strongest secondary flow of 4.5% Ub. The varying flow topology is discussed as a result of the varying ridge dimensions.
Stable Inversion for Flexible Multibody Systems Using the ANCF
Authors: Drücker Svenja , Seifried Robert
Published: January 2021

Flexible robots are often non‐minimum phase systems. Thus, their inverse model must be computed by stable inversion. Here, a simplification to the stable inversion process is proposed, which enables its application to complex underactuated multibody systems. As an example, a flexible manipulator modeled by the absolute nodal coordinate formulation is considered.
Modelling shear wave propagation in soft tissue surrogates using a finite element‐ and finite difference method
Authors: Ohlsen Jakob , Neidhardt Maximilian , Schlaefer Alexander , Hoffmann Norbert
Published: January 2021

Shear Wave Elasticity Imaging (SWEI) has become a popular medical imaging technique [1] in which soft tissue is excited by the acoustic radiation forces of a focused ultrasonic beam. Tissue stiffness can then be derived from measurements of shear wave propagation speeds [2]. The main objective of this work is a comparison of a finite element (FEM) and a finite difference method (FDM) in terms of their computational efficiency when modeling shear wave propagation in tissue phantoms. Moreover, the propagation of shear waves is examined in experiments with ballistic gelatin to assess the simulation results. In comparison to the FEM the investigated FDM proves to be significantly more performant for this computing task.
Efficient mortar‐based algorithms for embedding 1D fibers into 3D volumes
Authors: Steinbrecher Ivo , Popp Alexander
Published: January 2021

Many composite materials are based on 1D fibers being embedded into 3D solid volumes, e.g. carbon‐fiber reinforced plastics in aerospace engineering or fiber‐reinforced concrete in civil engineering to name only two prominent examples. The present contribution highlights the most important numerical methods and algorithmic building blocks for an efficient analysis of such systems based on cutting‐edge finite element formulations for nonlinear beams and a novel beam‐to‐solid volume coupling approach inspired by classical mortar methods. A particular emphasis is put on the efficient parallel implementation for large‐scale simulations, which includes suitable procedures for domain partitioning and geometry‐based search.
Unsupervised Data Labeling on Graphs by Self‐Assignment Flows
Authors: Zisler Matthias , Zern Artjom , Boll Bastian , Petra Stefania , Schnörr Christoph
Published: January 2021

This paper extends the recently introduced assignment flow approach for supervised image labeling to unsupervised scenarios where no labels are given. The resulting self‐assignment flow takes a pairwise data affinity matrix as input data and maximizes the correlation with a low‐rank matrix that is parametrized by the variables of the assignment flow, which entails an assignment of the data to themselves through the formation of latent labels (feature prototypes). A single user parameter, the neighborhood size for the geometric regularization of assignments, drives the entire process. By smooth geodesic interpolation between different normalizations of self‐assignment matrices on the positive definite matrix manifold, a one‐parameter family of self‐assignment flows is defined. Accordingly, our approach can be characterized from different viewpoints, e.g. as performing spatially regularized, rank‐constrained discrete optimal transport, or as computing spatially regularized normalized spectral cuts. Regarding combinatorial optimization, our approach successfully determines completely positive factorizations of self‐assignments in large‐scale scenarios, subject to spatial regularization. Various experiments including the unsupervised learning of patch dictionaries using a locally invariant distance function, illustrate the properties of the approach.