Untersuchungen der instationären Strömungstopologie im Nachlauf einer Seehundvibrisse.

in Delgado, A.; Rauh, A.; Lienhart, H. (Eds.) et al Proceedings der 17.GALA-Fachtagung “Lasermethoden in der Strömungsmesstechnik“ (2009)

Die Vibrissen von Seehunden zeichnen sich durch eine komplizierte dreidimensionale Struk- turierung aus. Sie versetzen den Seehund in die Lage, hydrodynamische Nachlaufspuren von Beutefischen zu ... [more ▼]

Die Vibrissen von Seehunden zeichnen sich durch eine komplizierte dreidimensionale Struk- turierung aus. Sie versetzen den Seehund in die Lage, hydrodynamische Nachlaufspuren von Beutefischen zu detektieren. Mit Hilfe von Stereo- μ Piv Messungen an Seehundvibrissen konnte die stationäre Strömungstopologie des Vibrissennachlaufes ermittelt werden. Zum besseren Verständnis der Funktion der Vibrissenstrukturierung ist es notwendig, die instatio- näre Strömungstopologie zu kennen. Durch räumlich und zeitlich hochauflösende numeri- sche Verfahren konnte die instationäre Strömungstopologie im Nachlauf einer Seehund- vibrisse ermittelt werden. [less ▲]

Use of commercial simulation software for analyzing the dynamics of an injection-molding clamp unit

Doctoral thesis (2006)

Today, the interest in integrated dynamic analysis of mechatronic systems increases. Different approaches are possible depending on the nature of the system, on the required complexity of the model, or ... [more ▼]

Today, the interest in integrated dynamic analysis of mechatronic systems increases. Different approaches are possible depending on the nature of the system, on the required complexity of the model, or simply on the tools available to the engineer. During this work, the aim was to implement specialized commercial simulation software packages and to combine them in order to simulate the dynamic behavior of mechatronic systems as for example an injection molding machine. The multi-body simulation software is the backbone of the current analysis as it inherently models large non-linear motions. It is possible to account for the flexibility of components in the MBS model if necessary. Furthermore, other simulation codes were used to model the hydraulic and controls systems. The case studies show the interest and the potential of a combined analysis of mechatronic systems. Once the different sub-models, generated with the adequate simulation tool, have been successfully linked and validated by measurements, various scenarios can be simulated and analyzed. The model provides the engineer with an additional insight into the overall system and thus with a better understanding of its dynamic characteristics. The interactions between the subsystems, which may be of very distinctive nature, can be investigated. Generally, it is difficult to predict such relations intuitively. Finally, the model allows to simulate with different design parameters and to asses the effect of modifications to these on the overall performance of the machine. This helps to identify the significant parameters that are crucial for an optimized functioning. [less ▲]

Using Bayesian inference to recover the material parameters of a heterogeneous hyperelastic body

Scientific Conference (2016)

We present a method for calculating a Bayesian uncertainty estimate on the recovered material parameters of a heterogeneous geometrically non-linear hyperelastic body. We formulate the problem in the ... [more ▼]

We present a method for calculating a Bayesian uncertainty estimate on the recovered material parameters of a heterogeneous geometrically non-linear hyperelastic body. We formulate the problem in the Bayesian inference framework [1]; given noisy and sparse observations of a body, some prior knowledge on the parameters and a parameter-to-observable map the goal is to recover the posterior distribution of the parameters given the observations. In this work we primarily focus on the challenges of developing dimension-independent algorithms in the context of very large inverse problems (tens to hundreds of thousands of parameters). Critical to the success of the method is viewing the problem in the correct infinite- dimensional function space setting [2]. With this goal in mind, we show the use of automatic symbolic differentiation techniques to construct high-order adjoint models [3], scalable maximum a posteriori (MAP) estimators, and efficient low-rank update methods to calculate credible regions on the posterior distribution [4]. [less ▲]

Using mobile phone data for urban network state estimation

Scientific Conference (2018, June)

A UX Approach to Privacy and Security: the Impact of User, Contextual and System-Related Factors

in CHI Workshop Exploring Individual Diffferences in Privacy (2018, April)

This position paper lays out current and future studies which we conduct on the UX aspects of security and privacy, our goal being to understand which factors influence privacy-related decision-making. We ... [more ▼]

This position paper lays out current and future studies which we conduct on the UX aspects of security and privacy, our goal being to understand which factors influence privacy-related decision-making. We advocate using UX design methods in order to study interindividual differences, system-related and contextual factors involved in privacy and security attitudes and behaviors. These results will contribute to user-tailored and personalized privacy initiatives and guide the design of future technologies. [less ▲]

Value Stream Mapping (VSM) to Evaluate and Visualize Interrelated Process-Chains Regarding Circular Economy

in Advances in Production Management Systems. Artificial Intelligence for Sustainable and Resilient Production Systems (2021, August 31), 633

The concept of circular economy (CE) aims to close and slow resource loops without neglecting the goals of sustainable development. Recently, the concept received encouraging attention among researchers ... [more ▼]

The concept of circular economy (CE) aims to close and slow resource loops without neglecting the goals of sustainable development. Recently, the concept received encouraging attention among researchers and business experts to be a convenient solution to move away from the finite linear economy concept to a more sustainable solution. However, this change of paradigm is only possible if we consider systems in a holistic manner and can localize the preventing hurdles. Value stream mapping (VSM) is a commonly known lean method, used to develop current state visualization of product and information flows within organization, helping to seek weaknesses and improve process flows. The motivation of this paper is a new C-VSM model, which enables its users to evaluate and visualize connected process-chains regarding CE on different levels in a holistic manner. For this purpose, the traditional VSM model was adapted towards the needs and requirements of CE through the application of a new representation method, additional indicators, and an appropriated evaluation system. C-VSM is in line with the current political and industrial objectives to apply CE principles by enabling a holistic reflection and consideration of supply-chains (SCs) on different levels. The model itself is validated through an extensive cross-company case study. [less ▲]

Das Versprechen der Zirkularität

in Standort (2022)

Against the backdrop of the recent political dynamics in the EU and in many of its member states regarding the Circular Economy, the present article discusses the impact of the concept so far and the ... [more ▼]

Against the backdrop of the recent political dynamics in the EU and in many of its member states regarding the Circular Economy, the present article discusses the impact of the concept so far and the challenges related to its implementation. In particular, it sheds a critical light on the following three aspects: first, the selective reception of the approach by key actors in industry and politics; second, the obvious implementation problems in trade and industry; and third, the underlying, growth-fixated economic model. Results from our own empirical work on the Luxembourg construction industry illustrate the reasoning. The article argues for a holistic and growth-critical understanding of circularity that not only gives space to orientation of efficiency and consistency but above all also to considerations of sufficiency. [less ▲]

Vicinity Resource Cartography for Delay-Tolerant Networks: a Holistic Perspective

in 2010 IFIP W IRELESS D AYS (2010)

In this paper we propose a distributed algorithm allowing nodes in delay-tolerant networks to construct vicinity resource maps based on past encounters. Our algorithm estimates the availability of the ... [more ▼]

In this paper we propose a distributed algorithm allowing nodes in delay-tolerant networks to construct vicinity resource maps based on past encounters. Our algorithm estimates the availability of the following resources: energy, buffer space, and bandwidth. We then show how a store-carry-forward scheme may benefit from having access to these resource estimates. While knowledge about resources available in the vicinity allows nodes to implement meaningful custodian election strategies, an evaluation of available bandwidth and contact time allows them to carry out adaptive queue management strategies. Thus, such strategies can be approached from a holistic perspective based on the availability of the three resources under consideration in node proximity.We validate our model separately in time-varying and space-varying environments. In addition to synthetic mobility models (random waypoint) we validate our resource estimation in a disaster area mobility model (using Bonn motion traces). We show that by using this information a routing protocol may dramatically improve its delivery rate and energy overhead while keeping delivery latency almost constant. [less ▲]

Virtual Coach Reaches Out To Me

Conference given outside the academic context (2013)

The virtual node polygonal element method for nonlinear thermal analysis with application to hybrid laser welding

in International Journal of Heat and Mass Transfer (2013), 67

The nonlinear heat transfer process occurring during hybrid laser welding was simulated using the Virtual-node Polygonal Element (VPE) method within the framework of the Finite Element Method (FEM). To ... [more ▼]

The nonlinear heat transfer process occurring during hybrid laser welding was simulated using the Virtual-node Polygonal Element (VPE) method within the framework of the Finite Element Method (FEM). To achieve robustness in large-scale welding simulations, a dynamic mesh refinement with quadtree and octree data structures was used in the welding region. Accuracy, convergence and efficiency were verified by solving two and three dimensional problems. It is found that the present VPE can successfully simulate the hybrid laser welding process with good accuracy and convergence. The adaptive refined mesh box can synchronously move with the welding heat source, which dramatically reduces the number of field nodes. Compared with the standard FEM,the VPEM requires only approximately 42% of the total degrees of freedom used in standard FEM for the same accuracy. Furthermore, we compare the computational cost and accuracy of the method to that of the finite element method, the edge based virtual node polygonal element/virtual node method, the edge-based Smoothed Point Interpolation Meshless Method (ES-PIM), the edge-based Element (ES-PIM) the Element Free Galerkin (EFG) method and the Meshless Local Petrove-Galerkin Petrov-Galerkin (MLPG) method. Compared to all those methods, the proposed scheme is found competitive in terms of computational cost versus accuracy, and benefit from a simple implementation. © 2012 Elsevier B.V. All rights reserved. [less ▲]