bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat Transfer Modeling of Confined Bubble Evaporation in a Microchannel
Authors: Sadir Sahba , Talebi Mohammadmahdi , Woias Peter , Dittmeyer Roland , Frohnapfel Bettina , Stroh Alexander 
Published: November 2019

AbstractIn this study, we model the heat transfer mechanism for a single nucleate vapor bubble which then expands to an elongated bubble during evaporation in a microchannel. The model is a logical mix of empirical correlations and analytical models and is defined for the two steps of bubble growth including: (a) partially confined growth, in which the bubble expands from nucleation site until it fills the entire cross‐section of the channel, and (b) fully confined growth, in which the bubble reaches the side walls and begins to elongate axially in downstream direction. To estimate the heat transfer characteristics of vapor bubble growth during evaporation in the microchannel, the time variation of liquid film thickness and bubble nose position are evaluated. Finally, a time‐averaged value of local heat transfer coefficient is obtained for a period of time using available heat transfer correlations for each heat transfer process separately.
Multiscale analysis of heterogeneous materials in boundary representation
Authors: Praster Maximilian , Reichel Rainer , Klinkel Sven 
Published: November 2019

AbstractThis paper deals with a numerical method for modeling heterogeneous materials with nonlinear behavior. Many novel high‐performance materials consist of different components. In the frame of nonlinear behavior the resulting macroscopic material properties cannot be determined without great experimental effort. In order to simulate the nonlinear material behavior, a nested finite element method (FE2) is used. An accompanying homogenization is performed for each load step. The material behavior is determined from the represented volume element (RVE) on the heterogeneous micro structure. The present approach is dealing with a discretization method of the heterogeneous structure. It based on the geometrical data of the interface boundary of the different constituents. A quad‐tree algorithm, in combination with a trimming algorithm is used for the mesh generation. Based on the geometrical data it yields an initial mesh for the analysis. Within the algorithm a staircase approximation of voids or inclusions is circumvented. However, the resulting mesh yields polygonal elements with an arbitrary number of nodes on the element boundary. To this end a novel polygonal element formulation is provided. It is based on the scaled boundary finite element method (SBFEM). The basic idea is to scale the boundary representation in relation to a scaling center. In contrast to SBFEM the present method makes us of an approximation of the displacement response in scaling direction. This enables the analysis of geometrical and material‐related nonlinear problems in solid mechanics. The interpolation at the boundary in circumferential direction is independent of the interpolation in scaling direction. This allows for novel refinement strategies, where e.g. p‐refinement is only applied for the interior element domain. The internal degrees of freedom are eliminated by static condensation. It leads to an element formulation with an arbitrary number of nodes at the element boundary. Thus, the present element is perfectly suited for a quad‐tree meshing algorithm of the RVE. Its hierarchical, tree‐like data structure makes it very useful for adaptive mesh refinements of complex geometries and regions with localized gradients. The classical hanging‐nodes problem for standard elements is omitted by the present element formulation. Some numerical examples show the capability of the formulation with respect to the numerical homogenization of heterogeneous materials.
Thermo‐mechanical fluid‐structure interaction for thermal buckling
Authors: Martin Katharina , Reese Stefanie 
Published: November 2019

AbstractAerothermodynamical loads cause buckling and plastic deformation of thin‐walled structures under boundary conditions, which restrict the structural movement. We present the numerical computation of a loosely coupled fluid‐structure interaction for thermal buckling. The task of the research is to provide a mechanical model which incorporates the correct material behaviour and is suitable for thermal panel buckling. For this, an elasto‐viscoplastic material model with non‐linear isotropic hardening is used, which also includes nonlinearly temperature dependent material parameters. This material model is implemented into a user material in Abaqus FEA. The structural computation is coupled with the fluid computation within the fluid‐structure interaction code ifls from the TU Braunschweig. For the fluid solver TAU from the DLR is used.
On the fracture behavior of vitreous two‐dimensional silica
Authors: Bamer Franz , Ebrahem Firaz , Stratmann Jan , Markert Bernd 
Published: November 2019

AbstractIn this paper, we present an athermal mechanical investigation of a two‐dimensional silica glass. We generate the network artificially using a Monte Carlo bond switch algorithm and compare our network with experimental results. Using an athermal quasistatic mechanical deformation method, we show that the two‐dimensional network glass reveals ductile fracture behavior, whereas the crystalline polymorph behaves purely brittle.
On the implementation of rate‐independent gradient‐enhanced crystal plasticity theory
Authors: Fohrmeister Volker , Klinge Sandra , Mosler Jörn 
Published: November 2019

AbstractIn the present work, classical local crystal plasticity is reformulated using incremental energy minimization. The resulting constrained optimization problem is efficiently solved by a nonlinear complementary problem, which additionally solves the problem of determination of the set of active slip systems. The model is extended to a nonlocal, gradient‐enhanced, formulation by employing and adapting the micromorphic approach. By doing so, the implementation of the gradient‐enhanced model is almost identical to that of the original local one, with the exception of additional balance equations.
Stress response of 2D silica under quasi‐static tension
Authors: Ebrahem Firaz , Bamer Franz , Markert Bernd 
Published: November 2019

AbstractWe use classical molecular dynamics simulations to generate topologically different models of vitreous 2D silica, all of which are subjected to quasi‐static tensile loading until fracture occurs. We demonstrate the effects of structural disorder on the material behaviour of 2D silica. For each sample, we determine the network structure by identifying the relative count of single rings and so‐called ring triplets each of which composed of three adjacent rings that share a common corner. In each sample, we spatially detect the first local atomic‐scale rearrangement during deformation and correlate it to the ring triplet involved.
Robust efficient global optimisation via adaptive surrogate refinement
Authors: Le Carrer Noémie , Moens David , Faes Matthias 
Published: November 2019

AbstractThrough the combination of a given surrogate model (e.g. Kriging) and a procedure allowing to compute the local optima of a given black‐box function (e.g. tuned Particle swarm optimization), our algorithm produces refined estimates of the global optima of a multidimensional black‐box model. A confidence ellipsoid computed in a Bayesian way is associated to each estimate, and shown to be reliable. The setting is tested on the 2‐dimensional Branin function. Results outperform those given by two state‐of‐the‐art non‐parallelised efficient global optimisation methods.
Contact Line Advection using the Level Set Method
Authors: Fricke Mathis , Marić Tomislav , Bothe Dieter 
Published: November 2019

AbstractIn this work, we consider the geometrical problem of the numerical advection of a hypersurface by a prescribed velocity field in the special case when the hypersurface intersects the domain boundary. This problem emerges from the discretization of continuum models for dynamic wetting. The kinematic evolution equation [1], [2] expresses the fundamental relationship between the rate of change of the contact angle and the structure of the transporting velocity field. We employ a simple version of the Level Set method to numerically solve the hyperbolic transport equation for the interface in two dimensions. The results are validated against an analytic solution of the kinematic evolution equation. Full access to the data and C++‐implementations is provided via an open research data repository [3].
Anisotropic Stiffness Degradation in Biaxial Tensile Testing of SMC
Authors: Lang Juliane , Schemmann Malte , Böhlke Thomas 
Published: November 2019

AbstractBiaxial tensile tests allow the investigation of damage evolution in sheet molding compound under biaxial stress states. This is of particular interest due to the different damage phenomena in composite materials. A key challenge is to find a suitable specimen design, because typical cruciform specimens fail in the arms before damage occurs in the area of interest which is the area of the biaxial stress state in the center area of the specimen. A specimen was found which enables the observation of anisotropic stiffness degradation which is one phenomenon of damage. In this proceedings the results of the experiments are presented.
Crack deflection in short fiber reinforced composites: Theory and experiment
Authors: Judt Paul , Ricoeur Andreas 
Published: November 2019

AbstractIn the past decades different crack growth and crack deflection criteria have been proposed, e.g. the maximum hoop stress criterion [1], the minimum strain energy density criterion [2] or the maximum energy release rate criterion [3]. These criteria were extended concerning phenomena such as crack path instability [4,5] and the anisotropy of fracture parameters [4]. Another approach for the prediction of crack growth and deflection angle is based on the Jk‐integral [6], assuming the crack to grow into the direction of the J‐vector [7]. The resulting deflection angles coincide well with those from other criteria in the case of small mixed‐mode ratios KII/KI or deflection angles, respectively. One challenge is the accurate calculation of the second coordinate J2 [8] and the appropriateness of this approach has been shown [9]. Nevertheless, in the cases of anisotropic crack resistance parameters, large mode‐II loading or unstable crack paths, the classical J‐vector criterion fails.In this paper, an extended J‐vector criterion is introduced providing the crack growth direction in the case of anisotropic fracture parameters and elastic constants [9,10]. The theory is validated by experimental results for different anisotropy ratios and orientations.
On the development of continuum material models for 2D materials from Density Functional Theory data
Authors: Shirazian Farzad , Hu Ming , Sauer Roger A. 
Published: November 2019

AbstractA multiscale framework is presented for the development of continuum models for 2D materials. The framework consists of four steps. First the 2D material is studied by performing a set of Density Functional Theory (DFT) simulations. A continuum model consistent with the material properties is then developed. The continuum model is calibrated based on the generated DFT data. Finally, the model is validated from new DFT data. The generation of DFT results and the calibration of the continuum model are discussed in this paper and a numerical example of a pressurized square phosphorus sheet is presented. The framework has previously been applied to graphene and single layer blue phosphorus.
Optimal control of district heating networks
Authors: Linn Dominik , Mohring Jan , Siedow Norbert 
Published: November 2019

AbstractStandard models for district heating networks usually lead to a high number of coupled nonlinear and algebraic equations, which makes an optimal control of such networks a difficult task. We present an iterative algorithm, in which we separately resolve the high dimensional equality constraints, leaving us with a series of low dimensional quadratic programs with linear inequality constraints, which can be solved by established methods.
Computer simulations in lectures in mathematics and in the natural sciences: learning‐theoretical aspects
Authors: Gunesch Roland 
Published: November 2019

AbstractThis article presents an overview of results from the mathematics education literature about the usefulness of using computer simulations in lectures in mathematics and in the natural sciences. Therefore, it justifies (some) established teaching practices in mathematics lectures. This arcitle discusses some key differences between computer simulations used for scientific research and simulations used for teaching. We describe some aspects of learning theory which are useful for analyzing computer simulations of mathematical phenomena.
Reduction of nonlinear dynamical systems excited by random loads
Authors: Dostal Leo 
Published: November 2019

AbstractThe presented research deals with methods for the study of complex interactions between noise and nonlinearities in dynamical systems. Practical applications of this research are beginning to appear across the spectrum of mechanics; for example vibration absorbers, ship dynamics, energy harvesting, and variable speed machining processes. In the presented approach perturbed Hamiltonian systems are considered, which are damped and excited by an absolutely regular non‐white Gaussian process. Analytical and semi‐analytical solutions to the corresponding nonlinear stochastic differential equations (SDE) are determined. The approach is based on a limit theorem by Khashminskii, from which a class of methods has been derived known as stochastic averaging. In the presented approach Homoclinic orbits, which divide the phase space of the corresponding Hamiltonian flow into different regions, are mapped to a graph in the one degree of freedom case. For two degree of freedom systems this procedure results in a mapping to a book, and so on for higher degrees of freedom. From the drift and diffusion of the resulting averaged process, probability density functions and first passage times are obtained.
Space‐Time Isogeometric Analysis of Parabolic Diffusion Problems in Moving Spatial Domains
Authors: Kyas Svetlana , Langer Ulrich , Repin Sergey 
Published: November 2019

AbstractThis paper addresses locally stabilized space‐time isogeometric (IgA) schemes for parabolic diffusion problems in moving spatial domains. It generalizes the results of our preceding works for problems in fixed spatial domains. We present functional a posteriori error estimates and study adaptive numerical procedures based on them and on truncated hierarchical B‐splines.
DNAJB1‐PRKACA–positive metastatic fibrolamellar carcinoma with unknown primary in a pediatric patient
Authors: Balbeur Samuel , Dumortier Adeline , Mergen Julien , Libbrecht Louis , Torbenson Michael , Boulanger Cecile , de Ville de Goyet Maelle , Van Damme An , Brichard Bénédicte 
Published: November 2019

AbstractFibrolamellar carcinoma (FLC) is a rare variant of hepatocellular carcinoma, occurring in children and young adults without underlying liver disease. The diagnosis is based on morphological characteristics of the tumor, supplemented by immunohistochemistry and/or genetic testing. Recently, the presence of a characteristic DNAJB1‐PRKACA fusion gene has been associated with FLC. Herein, we report a case of FLC presenting as peritoneal carcinomatosis in a 14‐year‐old female. Interestingly, no liver tumor was seen on imaging, and an alternative possibility is that the tumor arose outside the liver as a hepatoid carcinoma with fibrolamellar features.
Intravenous immunoglobulin therapy enhances suppressive regulatory T cells and decreases innate lymphoid cells in children with immune thrombocytopenia
Authors: Wang Shih‐Chung , Yang Kuender D. , Lin Ching‐Yuang , Huang Alex Y. , Hsiao Chien‐Chou , Lin Ming‐Tsan , Tsai Yi‐Giien 
Published: November 2019

AbstractBackgroundThis study aimed to investigate the relationship between CD4+ regulatory T cells (Tregs) and innate lymphoid cells (ILCs) in children with primary immune thrombocytopenia (ITP) undergoing high‐dose intravenous immunoglobulin (IVIG) therapy.MethodsWe enrolled a cohort of 30 children with newly diagnosed ITP and 30 healthy controls and collected blood samples for levels of Tregs, ILCs, relevant cytokines, and Treg suppression assay at the diagnosis, two days, four weeks, and one year (only platelet count) after high‐dose IVIG treatment. IVIG partial responders was defined by a platelet count less than 100 × 109/L at 12 months after IVIG treatment.ResultsChildren with newly diagnosed ITP exhibited elevated levels of ILC1, ILC2, ILC3, Th17, myeloid dendritic cells (DCs), plasmacytoid DCs, and serum IFN‐γ and IL‐17A levels, accompanied by a decrease in IL‐10‐producing Tregs. High‐dose IVIG therapy reversed these aberrations. Platelet counts positively correlated with Tregs (rho = 0.72) and negatively correlated with both ILC1 (rho = −0.49) and ILC3 (rho = −0.60) (P < 0.05). Significantly lower Tregs and higher ILC1, ILC3, DCs, and serum IL‐17A levels were noted in the partial responders (n = 8) versus responders (n = 22; P < 0.05). We found that Tregs suppressed proliferation of ILCs and CD4+ T cells in CD25‐depleted peripheral PBMCs and enhanced the apoptosis of CD4+CD45RO+ T cells in vitro following IVIG therapy.ConclusionsEffective high‐dose IVIG therapy for children with newly diagnosed ITP appears to result in the induction of Tregs, which suppresses ILC proliferation in vitro and is associated with platelet response.
Brain‐derived neurotrophic factor levels in pediatric sickle cell disease
Authors: Lance Eboni I. , Barron‐Casella Emily , Everett Allen D. , Casella James F. 
Published: November 2019

AbstractBackgroundChildren with sickle cell disease (SCD) have an increased risk of neurological complications, particularly stroke and silent cerebral infarction (SCI). Brain‐derived neurotrophic factor (BDNF) is a nerve growth factor associated with neuronal survival, synaptic plasticity, elevated transcranial Doppler (TCD) velocities and increased risk of stroke in patients with SCD. The objective of this study was to analyze plasma BDNF protein levels in children with SCD participating in the Silent Cerebral Infarct Transfusion Multi‐Center Clinical Trial (SIT Trial), comparing plasma samples of children with SCD and SCI to plasma samples from children with SCD without SCI, as well as healthy pediatric control participants.ProcedureEntry, exit, and longitudinal blood samples were collected from 190 SIT Trial participants with SCD and healthy pediatric controls over time. BDNF levels were measured by enzyme‐linked immunosorbent assay. Sample collection was not optimized for measurements of BDNF, but factors affecting BDNF levels were accounted for in analyses.ResultsBDNF levels were significantly higher in children with SCD in comparison to healthy pediatric control subjects. BDNF levels significantly increased over time in SCD participants. BDNF levels did not show any significant associations with the presence or absence of SCI or new/progressive SCI/stroke or TCD velocities.ConclusionsPlasma BDNF levels are elevated and increase over time in children with SCD. Additional studies with more longitudinal samples are needed to address the reasons for those increased levels.
Outcomes following proton therapy for Ewing sarcoma of the cranium and skull base
Authors: Kharod Shivam M. , Indelicato Daniel J. , Rotondo Ronny L. , Mailhot Vega Raymond B. , Uezono Haruka , Morris Christopher G. , Bradfield Scott , Sandler Eric S. , Bradley Julie A. 
Published: November 2019

AbstractPurposeDespite the dosimetric advantages of proton therapy, little data exist on patients who receive proton therapy for Ewing sarcoma of the cranium and skull base. This study reports local disease control and toxicity in such patients.Materials/methodsWe reviewed 25 patients (≤21 years old) with nonmetastatic Ewing sarcoma of the cranium and skull base treated between 2008 and 2018. Treatment toxicity was graded per the Common Terminology Criteria for Adverse Events v4.0. The Kaplan‐Meier product limit method provided estimates of disease control and survival.ResultsMedian patient age was 5.9 years (range, 1–21.7). Tumor subsites included the skull base (48%), non‐skull‐base calvarial bones (28%), paranasal sinuses (20%), and nasal cavity (4%). All patients underwent multiagent alkylator‐ and anthracycline‐based chemotherapy; 16% underwent gross total resection (GTR) before radiation. Clinical target volume (CTV) 1 received 45 GyRBE and CTV2 received 50.4 GyRBE following GTR or 54–55.8 GyRBE following biopsy or subtotal resection. Median follow‐up was 3.7 years (range, 0.26–8.3); no patients were lost. The 4‐year local control, disease‐free survival, and overall survival rates were 96%, 86%, and 92%, respectively. Two patients experienced in‐field recurrences. One patient experienced bilateral conductive hearing loss requiring aids, two patients developed intracranial vasculopathy, and 6 patients required hormone replacement therapy for neuroendocrine deficits. None developed a secondary malignancy.ConclusionProton therapy is associated with a favorable therapeutic ratio in children with large Ewing tumors of the cranium and skull base. Despite its high conformality, we observed excellent local control and no marginal recurrences. Treatment dosimetry predicts limited long‐term neurocognitive and neuroendocrine side effects.
Incidence of chromosomal anomalies in fetuses with isolated right aortic arch: A meta‐analysis
Authors: Luo Qingyi , Chen Jian , Zhang Yu , Li Jianhua , Su Xuan , Wang Qinghui , Ding Yunchuan 
Published: November 2019

AbstractObjectiveRight aortic arch (RAA) can be associated with chromosomal anomalies. However, the incidence of chromosomal anomalies when RAA is isolated (iRAA), ie, not associated with intracardiac anomalies, varies between different studies (0%‐28.5%). We have performed a meta‐analysis to allow a more accurate prenatal counselling.MethodsWe searched PubMed, Embase, and Web of Science for articles related to chromosomal anomalies among iRAA fetuses until April 2019. A total of 22 relevant studies, including 670 fetuses, were selected in the final meta‐analysis.ResultsThe results revealed that the overall rates of chromosomal anomalies and 22q11.2 deletion in iRAA fetuses were 7.5% (95% confidence interval [CI], 4.7%‐10.8%) and 4.3% (95% CI, 2.6%‐6.4%), respectively, while the rates were lower in iRAA without extracardiac anomalies, 4.7% (95% CI, 1.1%‐10.8%) and 2.4% (95% CI, 0.5%‐5.7%). The rate of chromosomal or copy number variants including 22q11.2 deletion identified by chromosomal microarray analysis (CMA) in iRAA fetuses was 8.2% (95% CI, 5.0%‐12.1%) and 3.7% (95% CI, 1.7%‐6.6%), respectively, compared with 5.1% (95% CI, 2.5%‐8.4%) and 2.4% (95% CI, 0.7%‐5.1%) identified by traditional karyotyping.ConclusionsA considerable proportion of iRAA cases have associated chromosomal anomalies and prevalence of associated 22q11.2 deletion, and CMA is recommended if invasive prenatal testing is performed.