TY - CHAP A1 - Harzheim, Thomas A1 - Heuermann, Holger T1 - Phase Repeatable Synthesizers as a New Harmonic Phase Standard for Nonlinear Network Analysis T2 - IEEE Transactions on Microwave Theory and Techniques Y1 - 2018 U6 - https://doi.org/10.1109/TMTT.2018.2817513 SP - 1 EP - 8 PB - IEEE ER - TY - JOUR A1 - Michel, Philipp A1 - Butenweg, Christoph A1 - Kinkel, Sven T1 - Pile-grid foundations of onshore wind turbines considering soil-structure-interaction under seismic loading JF - Soil Dynamics and Earthquake Engineering N2 - In recent years, many onshore wind turbines are erected in seismic active regions and on soils with poor load bearing capacity, where pile grids are inevitable to transfer the loads into the ground. In this contribution, a realistic multi pile grid is designed to analyze the dynamics of a wind turbine tower including frequency dependent soil-structure-interaction. It turns out that different foundations on varying soil configurations heavily influence the vibration response. While the vibration amplitude is mostly attenuated, certain unfavorable combinations of structure and soil parameters lead to amplification in the range of the system's natural frequencies. This testifies the need for overall dynamic analysis in the assessment of the dynamic stability and the holistic frequency tuning of the turbines. Y1 - 2018 U6 - https://doi.org/10.1016/j.soildyn.2018.03.009 SN - 0267-7261 VL - 109 SP - 299 EP - 311 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ciritsis, Alexander A1 - Horbach, Andreas A1 - Staat, Manfred A1 - Kuhl, Christiane K. A1 - Kraemer, Nils Andreas T1 - Porosity and tissue integration of elastic mesh implants evaluated in vitro and in vivo JF - Journal of Biomedical Materials Research: Part B: Applied Biomaterials N2 - Purpose In vivo, a loss of mesh porosity triggers scar tissue formation and restricts functionality. The purpose of this study was to evaluate the properties and configuration changes as mesh deformation and mesh shrinkage of a soft mesh implant compared with a conventional stiff mesh implant in vitro and in a porcine model. Material and Methods Tensile tests and digital image correlation were used to determine the textile porosity for both mesh types in vitro. A group of three pigs each were treated with magnetic resonance imaging (MRI) visible conventional stiff polyvinylidene fluoride meshes (PVDF) or with soft thermoplastic polyurethane meshes (TPU) (FEG Textiltechnik mbH, Aachen, Germany), respectively. MRI was performed with a pneumoperitoneum at a pressure of 0 and 15 mmHg, which resulted in bulging of the abdomen. The mesh-induced signal voids were semiautomatically segmented and the mesh areas were determined. With the deformations assessed in both mesh types at both pressure conditions, the porosity change of the meshes after 8 weeks of ingrowth was calculated as an indicator of preserved elastic properties. The explanted specimens were examined histologically for the maturity of the scar (collagen I/III ratio). Results In TPU, the in vitro porosity increased constantly, in PVDF, a loss of porosity was observed under mild stresses. In vivo, the mean mesh areas of TPU were 206.8 cm2 (± 5.7 cm2) at 0 mmHg pneumoperitoneum and 274.6 cm2 (± 5.2 cm2) at 15 mmHg; for PVDF the mean areas were 205.5 cm2 (± 8.8 cm2) and 221.5 cm2 (± 11.8 cm2), respectively. The pneumoperitoneum-induced pressure increase resulted in a calculated porosity increase of 8.4% for TPU and of 1.2% for PVDF. The mean collagen I/III ratio was 8.7 (± 0.5) for TPU and 4.7 (± 0.7) for PVDF. Conclusion The elastic properties of TPU mesh implants result in improved tissue integration compared to conventional PVDF meshes, and they adapt more efficiently to the abdominal wall. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 827–833, 2018. Y1 - 2018 U6 - https://doi.org/10.1002/jbm.b.33877 SN - 1552-4981 VL - 106 IS - 2 SP - 827 EP - 833 PB - Wiley CY - New York, NY ER - TY - JOUR A1 - Matcha, Heike A1 - Ljubas, Ante A1 - Gueldemet, Harun ED - Kepczynska-Walczak, A. T1 - Printing a Coffee Bar: An investigation into mid-scale 3D printing JF - Computing for a better tomorrow - Proceedings of the 36th eCAADe Conference - Volume 2, Lodz University of Technology, Lodz, Poland, 19-21 September 2018 N2 - We present and discuss an exploration of the possibilities and properties of 3D printing with a printing space of 1 cubic meter, and how those can be integrated into architectural education through an experimental design and research course with students of architecture.We expand on issues presented at the eCAADe conference 2017 in Rome [Ref 6] by increasing the complexity and size of our prints, printing not a model to scale, but a full scale funtional prototype of a usable architectural object: A coffee bar. Y1 - 2018 SP - 59 EP - 68 ER - TY - CHAP A1 - Stenger, David A1 - Altherr, Lena A1 - Müller, Tankred A1 - Pelz, Peter F. T1 - Product family design optimization using model-based engineering techniques T2 - Operations Research Proceedings 2017 N2 - Highly competitive markets paired with tremendous production volumes demand particularly cost efficient products. The usage of common parts and modules across product families can potentially reduce production costs. Yet, increasing commonality typically results in overdesign of individual products. Multi domain virtual prototyping enables designers to evaluate costs and technical feasibility of different single product designs at reasonable computational effort in early design phases. However, savings by platform commonality are hard to quantify and require detailed knowledge of e.g. the production process and the supply chain. Therefore, we present and evaluate a multi-objective metamodel-based optimization algorithm which enables designers to explore the trade-off between high commonality and cost optimal design of single products. Y1 - 2018 SN - 978-3-319-89919-0 U6 - https://doi.org/10.1007/978-3-319-89920-6_66 SP - 495 EP - 502 PB - Springer CY - Cham ER - TY - JOUR A1 - Franzen, Julius A1 - Pinders, Erik A1 - Pfaff, Raphael A1 - Enning, Manfred T1 - RailCrowd’s virtual fleets: Make most of your asset data JF - Deine Bahn N2 - For smaller railway operators or those with a diverse fleet, it can be difficult to collect sufficient data to improve maintenance programs. At the same time, new rules such as entity in charge of maintenance – ECM – regulations impose an additional workload by requiring a dedicated maintenance management system and specific reports. The RailCrowd platform sets out to facilitate compliance with ECM and similar regulations while at the same time pooling anonymised fleet data across operators to form virtual fleets, providing greater data insights. Y1 - 2018 SN - 0948-7263 IS - 9 SP - 11 EP - 13 PB - Bahn-Fachverlag CY - Berlin ER - TY - CHAP A1 - Pfaff, Raphael A1 - Melcher, Karin A1 - Franzen, Julian T1 - Rare event simulation to optimise maintenance intervals of safety critical redundant subsystems T2 - Proceedings of the European Conference of the PHM Society Y1 - 2018 VL - 4 IS - 1 SP - 1 EP - 6 ER - TY - JOUR A1 - Bung, Daniel Bernhard A1 - Valero, Daniel T1 - Re-aeration on stepped spillways with special consideration of entrained and entrapped air JF - Geosciences N2 - As with most high-velocity free-surface flows, stepped spillway flows become self-aerated when the drop height exceeds a critical value. Due to the step-induced macro-roughness, the flow field becomes more turbulent than on a similar smooth-invert chute. For this reason, cascades are oftentimes used as re-aeration structures in wastewater treatment. However, for stepped spillways as flood release structures downstream of deoxygenated reservoirs, gas transfer is also of crucial significance to meet ecological requirements. Prediction of mass transfer velocities becomes challenging, as the flow regime differs from typical previously studied flow conditions. In this paper, detailed air-water flow measurements are conducted on stepped spillway models with different geometry, with the aim to estimate the specific air-water interface. Re-aeration performances are determined by applying the absorption method. In contrast to earlier studies, the aerated water body is considered a continuous mixture up to a level where 75% air concentration is reached. Above this level, a homogenous surface wave field is considered, which is found to significantly affect the total air-water interface available for mass transfer. Geometrical characteristics of these surface waves are obtained from high-speed camera investigations. The results show that both the mean air concentration and the mean flow velocity have influence on the mass transfer. Finally, an empirical relationship for the mass transfer on stepped spillway models is proposed. Y1 - 2018 SN - 2076-3263 VL - 8 IS - 9 SP - Article number 333 PB - MDPI CY - Basel ER - TY - JOUR A1 - Valero, Daniel A1 - Bung, Daniel Bernhard T1 - Reformulating self-aeration in hydraulic structures: Turbulent growth of free surface perturbations leading to air entrainment JF - International Journal of Multiphase Flow N2 - A new formulation for the prediction of free surface dynamics related to the turbulence occurring nearby is proposed. This formulation, altogether with a breakup criterion, can be used to compute the inception of self-aeration in high velocity flows like those occurring in hydraulic structures. Assuming a simple perturbation geometry, a kinematic and a non-linear momentum-based dynamic equation are formulated and forces acting on a control volume are approximated. Limiting steepness is proposed as an adequate breakup criterion. Role of the velocity fluctuations normal to the free surface is shown to be the main turbulence quantity related to self-aeration and the role of the scales contained in the turbulence spectrum are depicted. Surface tension force is integrated accounting for large displacements by using differential geometry for the curvature estimation. Gravity and pressure effects are also contemplated in the proposed formulation. The obtained equations can be numerically integrated for each wavelength, hence resulting in different growth rates and allowing computation of the free surface roughness wavelength distribution. Application to a prototype scale spillway (at the Aviemore dam) revealed that most unstable wavelength was close to the Taylor lengthscale. Amplitude distributions have been also obtained observing different scaling for perturbations stabilized by gravity or surface tension. The proposed theoretical framework represents a new conceptualization of self-aeration which explains the characteristic rough surface at the non-aerated region as well as other previous experimental observations which remained unresolved for several decades. Y1 - 2018 U6 - https://doi.org/10.1016/j.ijmultiphaseflow.2017.12.011 SN - 0301-9322 VL - 100 SP - 127 EP - 142 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Altherr, Lena A1 - Brötz, Nicolas A1 - Dietrich, Ingo A1 - Gally, Tristan A1 - Geßner, Felix A1 - Kloberdanz, Hermann A1 - Leise, Philipp A1 - Pelz, Peter Franz A1 - Schlemmer, Pia A1 - Schmitt, Andreas T1 - Resilience in mechanical engineering - a concept for controlling uncertainty during design, production and usage phase of load-carrying structures JF - Applied Mechanics and Materials N2 - Resilience as a concept has found its way into different disciplines to describe the ability of an individual or system to withstand and adapt to changes in its environment. In this paper, we provide an overview of the concept in different communities and extend it to the area of mechanical engineering. Furthermore, we present metrics to measure resilience in technical systems and illustrate them by applying them to load-carrying structures. By giving application examples from the Collaborative Research Centre (CRC) 805, we show how the concept of resilience can be used to control uncertainty during different stages of product life. Y1 - 2018 SN - 1662-7482 U6 - https://doi.org/10.4028/www.scientific.net/AMM.885.187 VL - 885 SP - 187 EP - 198 PB - Trans Tech Publications CY - Bäch ER -