bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three‐dimensional echo planar spectroscopic imaging for differentiation of true progression from pseudoprogression in patients with glioblastoma
Authors: Verma Gaurav , Chawla Sanjeev , Mohan Suyash , Wang Sumei , Nasrallah MacLean , Sheriff Sulaiman , Desai Arati , Brem Steven , O'Rourke Donald M. , Wolf Ronald L. , Maudsley Andrew A. , Poptani Harish 
Published: December 2018

Accurate differentiation of true progression (TP) from pseudoprogression (PsP) in patients with glioblastomas (GBMs) is essential for planning adequate treatment and for estimating clinical outcome measures and future prognosis. The purpose of this study was to investigate the utility of three‐dimensional echo planar spectroscopic imaging (3D‐EPSI) in distinguishing TP from PsP in GBM patients. For this institutional review board approved and HIPAA compliant retrospective study, 27 patients with GBM demonstrating enhancing lesions within six months of completion of concurrent chemo‐radiation therapy were included. Of these, 18 were subsequently classified as TP and 9 as PsP based on histological features or follow‐up MRI studies. Parametric maps of choline/creatine (Cho/Cr) and choline/N‐acetylaspartate (Cho/NAA) were computed and co‐registered with post‐contrast T1‐weighted and FLAIR images. All lesions were segmented into contrast enhancing (CER), immediate peritumoral (IPR), and distal peritumoral (DPR) regions. For each region, Cho/Cr and Cho/NAA ratios were normalized to corresponding metabolite ratios from contralateral normal parenchyma and compared between TP and PsP groups. Logistic regression analyses were performed to obtain the best model to distinguish TP from PsP. Significantly higher Cho/NAA was observed from CER (2.69 ± 1.00 versus 1.56 ± 0.51, p = 0.003), IPR (2.31 ± 0.92 versus 1.53 ± 0.56, p = 0.030), and DPR (1.80 ± 0.68 versus 1.19 ± 0.28, p = 0.035) regions in TP patients compared with those with PsP. Additionally, significantly elevated Cho/Cr (1.74 ± 0.44 versus 1.34 ± 0.26, p = 0.023) from CER was observed in TP compared with PsP. When these parameters were incorporated in multivariate regression analyses, a discriminatory model with a sensitivity of 94% and a specificity of 87% was observed in distinguishing TP from PsP. These results indicate the utility of 3D‐EPSI in differentiating TP from PsP with high sensitivity and specificity.
Determination of gait parameters in real‐world environment using low‐cost inertial sensors
Authors: Mundt Marion , Thomsen Wolf , Bamer Franz , Makert Bernd 
Published: December 2018

AbstractThe ageing society causes an increasing need for gait monitoring in daily life to preserve the mobility of older people. Therefore, flexible low‐cost and easy‐to‐apply sensor networks are necessary. This study evaluates two in‐house developed inertial sensors for their capability of detecting spatial and temporal parameters of gait by using a time‐warping algorithm for stride segmentation. Thereby, impaired or wheeled walker supported gait can be analysed using a patient specific template. The results prove the capability to exclude sequences from the motion that do not correspond to strides and to detect spatio‐temporal parameters reliably. For the application to geriatric patients, however, further research is necessary.
Characterization of the frequency‐dependent properties of damping materials
Authors: Duvigneau Fabian , Spannan Lars , Gavila Lloret Maria , Woschke Elmar , Gabbert Ulrich 
Published: December 2018

AbstractIn this paper an experimental method for determining the frequency‐dependent stiffness and damping properties is presented. The aim is to obtain valid input parameters for a simulation model that considers the most important effects of typical damping materials without the necessity of poroelastic material formulations, which require at least five different input parameters. These parameters are difficult and expensive to determine experimentally. Moreover, the determination procedure is not very robust and the results can easily vary [1]. Additionally, such parameters are often phenomenological without having a physical meaning. For these reasons, it is promising to use a simpler material model based on frequency‐dependent stiffness and damping parameters within numerical simulations in order to be able to predict the acoustic behavior of complex systems with different damping and insulation treatments sufficiently.
Adaptive numerical integration of broken finite cells based on moment fitting applied to finite strain problems
Authors: Hubrich Simeon , Düster Alexander 
Published: December 2018

AbstractIn the finite cell method (FCM) which is based on the fictitious domain approach the numerical integration of broken cells represents a major challenge. Commonly, an adaptive integration scheme is used which, usually, results in a large number of integration points and thus increases the numerical effort, especially for nonlinear applications. To reduce the number of integration points, we present an adaptive scheme which is based on moment fitting. Thereby, we introduce an approach based on Lagrange polynomials which avoids the necessity of solving the moment fitting equation system. We study the performance of this integration method considering two numerical examples for finite strain problems of the FCM.
A general framework for the thermodynamically consistent time integration of open nonlinear thermoelastic systems
Authors: Schiebl Mark , Betsch Peter 
Published: December 2018

AbstractThis work deals with Energy‐Momentum‐Entropy (EME) consistent methods of open thermoelastic systems. While Energy‐Momentum (EM) preserving integrators are well‐known for conservative mechanical systems, Romero introduced in [1] the class of thermodynamically consistent (TC) integrators for coupled thermomechanical systems, which further respect symmetries of the underlying coupled system and are capable of conserving associated momentum maps and can therefore also be termed EME schemes in analogy to EM schemes for conservative systems. As mathematical framework for the geometric structure of the non‐equilibrium thermodynamics the GENERIC (General Equation for Non‐Equilibrium Reversible‐Irreversible Coupling) framework, originally introduced for complex fluids in [2], is used. Since the GENERIC framework does not depend on a specific choice of the thermodynamical state variables [3], we explore the structure of the GENERIC framework using the entropy density (see e.g. [4]), the absolute temperature (see e.g. [5]) and further the internal energy density as thermodynamical state variable. Applying the notion of a discrete gradient in the sense of [6] leads to an EME integrator. As boundary conditions rely on the specific choice of the thermodynamical state variable we extend the GENERIC framework to be suitable for open systems following the procedure in [7].
Modelling and Simulation of the Coating Process on Open Porous Metal Foams
Authors: Grill Christine , Jung Anne , Diebels Stefan 
Published: December 2018

AbstractBased on an increasing demand of energy and raw materials, resources should be used more efficiently. Therefore, multifunctional materials and lighter constructions, which can endure higher payloads, are needed. Cellular materials like metal foams are bionic, multifunctional materials, which can be optimised by a coating of the foam structure. Due to this coating via electrodeposition, the material properties per unit mass can be optimised. In consequence of the mass transport limitation inside the foam during the electrodeposition process, there occurs an inhomogeneous coating thickness distribution. To obtain a homogeneous coating thickness, in this project the factors are studied and simulated, which influence the electrochemical coating process. The electrodeposition process can be described by an ion source at the anode, the mass transport from anode to cathode and an ion sink at the cathode. The mass transport and the deposition process are characterised by the continuity equation with convection, diffusion, migration, a source term and a sink term. In this contribution, the factors influencing the coating thickness are investigated by numerical simulation to provide a homogeneous coating thickness. A material model is developed coupling mass transport with electrodeposition. A finite difference approach is used to simulate the ion concentration distribution inside the foam.
Experimental study and discrete element simulation of auger dosing of different pharmaceutical powders
Authors: El Kassem Bilal , Brinz Thomas , Heider Yousef , Markert Bernd 
Published: December 2018

AbstractIn pharmaceutical solid dosage forms development, the physical properties of powders play a significant role in their flowability and help in understanding the flow behavior and optimizing the design of powder handling equipment. In particular, powder flow depends strongly on the interparticulate interactions between the particles, where with more interactions, i.e. internal friction between particles, the less is the powder flowability and, thus, more power is required to accelerate the flow in the dosing machine.One of the main goals of this project is to implement high‐speed first‐in‐first‐out powder auger dosing of small quantities and accomplishing high dosing accuracy. Shear cell analysis and empirical methods are used to characterize powder flow. Different parameters including powder properties, geometry design and operating process conditions are used and altered accordingly based on design of experiments (DoE). Experimental studies and discrete element method (DEM) simulations on dosing different pharmaceutical powders are performed.
Numerically robust two‐scale full‐field finite strain crystal plasticity simulations of polycrystalline materials
Authors: Kochmann Julian , Wulfinghoff Stephan , Svendsen Bob , Reese Stefanie 
Published: December 2018

AbstractThe purpose of this work is the derivation of a numerically robust algorithmic formulation for the computation of the overall consistent algorithmic tangent moduli for the two‐scale modeling of heterogeneous materials with non‐linear constitutive behavior at finite strains. The underlying concept is a perturbation method. In contrast to existing numerical tangent computation algorithms, the proposed method yields the exact tangent using only six (instead of nine) perturbations (three in 2d). As an example, the FE‐FFT‐based approach by [6] is employed to predict the local and overall mechanical behavior of elasto‐viscoplastic polycrystals in a macroscopic Cook's membrane problem setting.
Characterization of Brake Shims Using Analytical Constrained Layer Damping Theories
Authors: Schmid Dominik , Gräbner Nils , von Wagner Utz 
Published: December 2018

AbstractShims in automotive brake systems are applied to suppress brake squeal resulting from self‐excited vibrations. These composite structures consist of thin metal plates and elastomer layers having high damping potential. The characterization and subsequent selection of shims is mainly based on a wide range of experimental investigations so far. To reduce measuring efforts significantly a systematic modeling of shims is focused. Therefore, approaches from literature describing surface damping treatments analytically are considered. The damping effect is mainly based on the shearing of the viscoelastic core which is taken into account by the applied theory. The dissipation potential is characterized by the complex shear modulus of the elastomer layer. Hence, sandwich beam theories enable the prediction of natural frequencies and in particular loss factors of bending mode shapes. In this contribution shims bonded on rectangular steel plates are examined. The main focus is on the determination of rheological influencing variables as well as the impact of boundary conditions in detail. Moreover, the impact of the shim length on the damping behavior is investigated experimentally.
Guided wave‐based damage detection in solids using computational intelligence
Authors: Hesser Daniel Frank , Markert Bernd 
Published: December 2018

AbstractThe field of structural health monitoring focuses on the non‐destructive evaluation of structures during on‐going operation. In this paper, the application of elastic guided waves in solids is discussed and applied to monitor an aluminium plate. The interaction of waves with structural features and uncertainties results into a unique wave field, which can be achieved by bonding piezoelectric sensors on the surface. These sensors allow a controlled excitation and acquisition of waves in structural components. In this study, the acquired data is processed by the help of computational intelligence. Computational intelligence enables the ability to learn wave behaviours from data of undamaged as well as damaged structures. Once the training process is completed, the trained system can be applied under operational conditions and will continuously monitor the structure and detect the location of damage.
Modelling the anisotropic in‐plane and out‐of‐plane elastic‐plastic response of paper
Authors: Alajami Ahmad , Li Yujun , Simon Jaan‐Willem 
Published: December 2018

AbstractLaminated paperboard is one of the main materials used in packaging products. The technical processes used for manufacturing such materials lead to a sepcial fiber structure that gives the material anisotropic behavior which can be observed in experiments. Two different directions can be distinguished;the in‐plane and the out‐of‐plane directions, which both experience an elastic‐plasctic behavior, where a permanent deformation is observed after unloading in both directions. The out‐of‐plane behavior includes additional aspects such as the densification and internal friction effects. These effects are significant to investigate especially in the large deformations range, which can be observed during different forming processes of the paperboard. For these reasons, an in‐plane and an out‐of‐plane models were introudced. Each model works independently from the other one. The models were formulated based on the finite strain elasto‐plasticity framework, which gives the possiblity to investigate the behavior of paperboard under large deformations. As a result, the current model was able to represent the main aspects of the behavior of paperboard in both in‐plane and out‐of‐plane directions.
On the back calculation of material strength values from strength test results
Authors: Schagerl Martin , Grillenberger Markus 
Published: December 2018

AbstractThe determination of material strength parameters from structural test measurements yields in general an inverse problem. The measured test values are e.g. loads and displacements applied on the specimen. The unknown material parameters are e.g. local stress values at particular strain states. Naturally, material models should only contain material parameters which can be identified by such back calculation. However, if material models want to be practically useful, the back calculation should be a simple procedure, which is derived from adapted analytical and numerical models, and where the material parameters are gained in a most direct way. In a complete approach the introduction of a new constitutive model is accompanied with the specification of an according test setup and a validated evaluation procedure, with which the engineer can determine the occurring material parameters. The current article discusses this issue on hand of two simple, but non‐standard material strength data for metals: First, the flow curve under pure shear, which is determined by using a plane torsion test rig, and second, the compressive strength under high strain rates, which is determined by using a cam drive test rig. Both, analytical considerations and numerical Finite Element simulations are used for back calculation.
Micromechanical behavior of UHPC under cyclic bending‐tensile loading in consideration of the influence of the concrete edge zone
Authors: Harenberg Stefan , Caggiano Antonio , Koenig Andreas , Said Diego , Gilka‐Bötzow Albrecht , Schultz‐Cornelius Milan , Yang Sha , Pahn Matthias , Dehn Frank , Koenders Eddie 
Published: December 2018

AbstractThis paper provides preliminary results of a research study on the fatigue behavior of Ultra‐High‐Performance Concrete (UHPC). Results of an experimental campaign, performed at the Department of Concrete Structures and Structural Engineering of the TU‐Kaiserslautern, are firstly proposed. The heterogeneous meso‐structure and material degradation of UHPC are studied through cyclic bending‐tensile tests. A test set‐up is specially developed at the TU‐Kaiserslautern to perform such activities. Particularly, different upper stress cycles (namely, cycle reversals) characterized by different force/stress amplitudes are considered and analyzed. The influence of the edge zone on the stress cycles is tested on notched and normal specimens while the results are used for composing a so‐called “Wöhler curve” of the materials' fatigue behavior. Damage progress during loading is monitored by means of a Digital Image Correlation system (DIC) and the results are used for improving the measurement accuracy. Based on these results, macroscopic and mesoscale simulations are performed at the TU‐Darmstadt‘s Institute of Construction and Building Materials. A meso‐mechanical approach for the numerical analysis of UHPC specimens subjected to low‐ and high‐cycle fatigue actions will be presented. The possibilities of modeling the material fracture response induced by fatigue is taken into account by means of a systematic use of zero‐thickness interface elements equipped with a fracture‐based model and combined with a continuous damage constitutive law. A plastic‐damage based model for concrete subjected to cyclic loading is developed combining the concept of fracture‐energy theories with a stiffness degradation, representing the key phenomenon occurring in concrete under cyclic responses. The experimental and numerical activities proposed in this paper stem out from the DFG Priority Program 2020 Project “Cyclic Damage Processes in High‐Performance Concretes in the Experimental Virtual Lab”.
On the Kinematics of Contact Line Motion
Authors: Fricke Mathis , Köhne Matthias , Bothe Dieter 
Published: December 2018

AbstractWe investigate the moving contact line problem for two‐phase incompressible flows by a kinematic approach. The key idea is to derive an evolution equation for the contact angle assuming the transporting velocity field to be given. It turns out that the resulting equation expresses the time derivative of the contact angle in terms of the velocity gradient at the solid wall. Together with the additionally imposed boundary conditions for the velocity, it yields a more specific form of the contact angle evolution. In this paper we consider the Navier slip boundary condition, which is frequently used for the modeling of moving contact lines. Exploiting furthermore the interfacial transmission condition for the viscous stress, we derive an explicit form of the contact angle evolution for sufficiently regular solutions. In the absence of phase change it only involves the contact line velocity and the slip length from the Navier condition. From this equation we can read off the qualitative behavior of the contact angle evolution for sufficiently regular solutions to these models, which turns out to be unphysical.
Fault diagnosis using Probability of Detection (POD)‐based sensor/information fusion for vibration‐based analysis of elastic structures
Authors: Ameyaw Daniel Adofo , Rothe Sandra , Söffker Dirk 
Published: December 2018

AbstractThe Probability‐of‐Detection (POD) measure quantifies the performance of a measurement device to nondestructive testing taking into account statistical variability. The time and cost involved have given rise to Model‐Assisted POD to improve the effectiveness of POD models with little or no specimen testing. Similar criteria regarding capabilities of FDI (Fault Detection and Isolation) or diagnostic approaches applied to vibration‐based analysis are currently not known. This results from complexity of the dynamical behaviors in relation to faults, sensor positions (observability), and feature extraction tasks. In this contribution the complexity of POD‐based analysis applied to fault detection of elastic mechanical structures is examined. Based on experimental results of mechanical modifications on an elastic beam, the POD of different FDI‐procedures are examined. Different sensor types are used for eigenfrequency analysis. Depending on the modes considered it can be shown why this classical approach often does not lead to satisfying results. To fuse the POD values, suitable assumptions in combination with a new method are applied to eigenfrequency‐based analysis as detection task.
Value diversity and conservation conflict: Lessons from the management of red grouse and hen harriers in England
Authors: St John Freya A. V. , Steadman Janna , Austen Gail , Redpath Steve M. 
Published: December 2018

Abstract

Conflicts between people over wildlife management are damaging, widespread, and notoriously difficult to resolve where people hold different values and worldviews. Cognitive approaches examining steps from human thought to action can help us understand conflict and explore strategies for their management.

We focused on the conflict between hunters and conservationists over the management of red grouse (Lagopus lagopus scoticus) and hen harriers (Circus cyaneus) in the English uplands which represents a classic, persistent conflict, where human dimensions are poorly understood.

Guided by conceptual frameworks from social and environmental psychology, we conducted a questionnaire‐based study to assess wildlife value orientations of key stakeholders. We quantified attitudes towards hen harriers, grouse shooting, gamekeepers, and raptor conservationists. We also measured support/opposition for harrier management strategies in England and investigated trust in the responsible government authority.

We present data from 536 respondents from field sport or nature conservation organizations. Respondents were categorized according to the primary objectives of their affiliated organization: Field sport (i.e., hunters), Non‐raptor, Pro‐raptor, and Pro‐bird (i.e., organizations promoting conservation of birds excluding raptors, raptors specifically, or birds generally).

Utilitarian value orientations were prominent among Field sport and Non‐raptor respondents. Most Pro‐raptor and Pro‐bird participants held mutualist value orientations, indicating they did not support shooting or management of wildlife.

As suggested by the cognitive hierarchy, we found strong correlations between attitude and support for management options, our proxy for behaviour.

Pro‐bird affiliates showed clear preference for less invasive management, and along with Pro‐raptor respondents did not support brood management (removal and later release of eggs/young when harrier density is high). Field sport individuals expressed a degree of support for all management types. Trust in Natural England was limited.

Understanding value orientations and attitudes of stakeholders helps explain differences in levels of support for management approaches. Our study highlighted strongly divergent beliefs. Such positions are hard to change. Increasing the level of ecological knowledge alone is unlikely to facilitate conflict management. Instead, conflict management would benefit from combining such knowledge with a focus on relationships, deliberation, and trust in addition to exploring comanagement interventions.

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