Insight into cooperation processes for traffic scenarios: modelling with naturalistic decision making

With the introduction of automatic vehicle guidance (AV), mixed traffic scenarios between automatically and manually guided vehicles are to be expected, at least during a transitions phase. To ensure the safety of motor vehicle transportation, it will be essential to develop a cooperative relationship between human drivers and AV. Research in this area is currently being done to gain insight into the manner of human drivers’ decisions to transfer the same behaviours to automatic vehicle guidance. A lot of research is being done to prepare for the introduction of AV, but there is still a lack of information on how individual road users make decisions in cooperative decisions. Currently, there is no study that has tried to understand the decision-making process with the help of an online-survey. For that reason, a questionnaire study on cooperative traffic situations (N?=?281) was carried out, which was analysed with the Natural Decision Making approach. By means of the NDM approach and the use of the recognition module, links between planned action and the expected action between road users were identified. Furthermore, it was possible to categorize individual communication signals into offensive or defensive signals and thus make predictions about the intention of the driver. These findings can be used to derive design recommendations for automatic vehicle guidance in cooperative situations.     

A clip-on electroosmotic pump for oscillating flow in microfluidic cell culture devices

Recent advances in microfluidic devices put a high demand on small, robust and reliable pumps suitable for high-throughput applications. Here we demonstrate a compact, low-cost, directly attachable (clip-on) electroosmotic pump that couples with standard Luer connectors on a microfluidic device. The pump is easy to make and consists of a porous polycarbonate membrane and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrodes. The soft electrode and membrane materials make it possible to incorporate the pump into a standard syringe filter holder, which in turn can be attached to commercial chips. The pump is less than half the size of the microscope slide used for many commercial lab-on-a-chip devices, meaning that these pumps can be used to control fluid flow in individual reactors in highly parallelized chemistry and biology experiments. Flow rates at various electric current and device dimensions are reported. We demonstrate the feasibility and safety of the pump for biological experiments by exposing endothelial cells to oscillating shear stress (up to 5 dyn/cm²) and by controlling the movement of both micro- and macroparticles, generating steady or oscillatory flow rates up to ± 400 μL/min.     

Data-Mining-Cup 2007

Zusammenfassung  Die Aufgabe des Data-Mining-Cups 2007 war die Entwicklung einer vollautomatischen Methode zur effektiven Steuerung des Einsatzes von Rabattcoupons. Vorverarbeitung und Parameter wurden durch eine Kreuzvalidierung optimiert. Experimente zeigen, dass ein einzelner Klassifikator in der Regel nicht genügt, die Aufgabenstellung mit ausreichender Güte zu l?sen. Vielmehr müssen mehrere, m?glichst verschiedene, Klassifikatoren dazu herangezogen werden. Die eingereichten L?sungen entstanden durch Kombination von bis zu 2.000 Klassifikatoren und haben im Wettbewerb sehr gut abgeschnitten: Sechs von neun Abgaben lagen unter den ersten zehn Pl?tzen, die übrigen drei L?sungen sind immer noch unter den ersten 20 von insgesamt 230 Pl?tzen.     

From dynamic movement primitives to associative skill memories

In recent years, research on movement primitives has gained increasing popularity. The original goals of movement primitives are based on the desire to have a sufficiently rich and abstract representation for movement generation, which allows for efficient teaching, trial-and-error learning, and generalization of motor skills (Schaal 1999). Thus, motor skills in robots should be acquired in a natural dialog with humans, e.g., by imitation learning and shaping, while skill refinement and generalization should be accomplished autonomously by the robot. Such a scenario resembles the way we teach children and connects to the bigger question of how the human brain accomplishes skill learning. In this paper, we review how a particular computational approach to movement primitives, called dynamic movement primitives, can contribute to learning motor skills. We will address imitation learning, generalization, trial-and-error learning by reinforcement learning, movement recognition, and control based on movement primitives. But we also want to go beyond the standard goals of movement primitives. The stereotypical movement generation with movement primitives entails predicting of sensory events in the environment. Indeed, all the sensory events associated with a movement primitive form an associative skill memory that has the potential of forming a most powerful representation of a complete motor skill.     

Strain aging and strain rate sensitivity of oxygen-enriched (α + β) Zircaloy-2

The flow behavior of oxygen-enriched Zircaloy-2, with oxygen concentrations ranging from 1260 to 12360 ppm, was investigated over the (α +β) phase field and parts of the adjacent α andβ phase regions. The flow curves were determined in compression at constant true strain rates in the range 10^-4 to 10^-1 s^-1, and the strain aging response was evaluated from the relative yield drops observed in interrupted tests. Unlike those of the single phase materials, the flow curves of the (α +β) alloys were characterized by large yield drops. These were strongly dependent on temperature, strain rate, prestrain, and phase proportion, and attained a peak value at temperatures corresponding to aβ fraction of 0.5 to 0.8. The activation energy for strain aging increased from 220 to 340 kJ/mol with an increase in oxygen concentration from 4180 to 12360 ppm. The strain aging effect is attributed to the solutes Fe and Cr, which concentrate in theβ phase and probably form ordered zones of Zr(Fe,Cr)₂ on the hot work substructure. The strain rate sensitivitym increased with temperature for both the fullya and fullyβ alloys, withm _gb = 2 m_α. In the (α +β) range, a slight maximum inm was observed in the lowβ fraction (i. e., 0.2 to 0.4β) region and a minimum in the largeβ fraction (J. e., 0.6 to 0.8β) region. The maximum is ascribed to the softβ film which forms around thea grains, whereas the minimum is attributed to the occurrence of strain aging in this range.     

Modeling of the plastic anisotropy of textured sheet

An alternative is proposed to the classical crystallographic and continuum techniques for representation of polycrystal anisotropy. It involves the use of continuum yield criteria to reproduce the yielding behavior of a collection of disoriented grains displaying typical experimental spreads. It is shown that the anisotropic properties pertaining to single ideal orientations are readily assessed. Yield surfaces as well as strain rateR(θ) and yield stressσ(θ)/σ(0) ratios are calculated for polycrystalline materials displaying several texture components. The Taylor, Sachs, and Kochendörfer grain interaction models are used for this purpose, the last of which leads to the fastest computations because it permits the texture/plastic properties relationship to be described analytically. Such methods are particularly well suited to FEM and CAD-CAM calculations. The predictions obtained from the present analysis are compared to experimental observations reported in the literature.     

Ti(CN) precipitation in microalloyed austenite during stress relaxation

Stress relaxation tests were carried out on a 0.05 pct C-0.007 pct N-0.25 pct Ti steel preheated to 1260 °C and then held in the temperature range 900 to 1050 °C. The precipitation of Ti(CN) that took place was followed by extraction replication. Dense precipitates were observed when stress plateaus appeared on the relaxation curves. The cube-shaped Ti(CN) precipitates were heterogeneously distributed in either a chain-like or a cell-like manner, indicating that the precipitates were nucleated on dislocations or on dislocation substructures. The changes in the size distribution of the precipitates during relaxation were also followed and analyzed in terms of the Zener diffusion controlled particle growth theory. The results suggest that Ti(CN) precipitation under the present experimental conditions proceeds in three sequential stages: (i) nucleation and growth according to a parabolic law; (ii) nucleation site saturation accompanied by growth alone; and (iii) Ostwald ripening. The time dependence of the mean Ti(CN) particle size is nonlinear during the first, and becomes linear during the second stage.     

On compliance and buckling objective functions in topology optimization of snap-through problems

This paper deals with topology optimization of static geometrically nonlinear structures experiencing snap-through behaviour. Different compliance and buckling criterion functions are studied and applied for topology optimization of a point loaded curved beam problem with the aim of maximizing the snap-through buckling load. The response of the optimized structures obtained using the considered objective functions are evaluated and compared. Due to the intrinsic nonlinear nature of the problem, the load level at which the objective function is evaluated has a tremendous effect on the resulting optimized design. A well-known issue in buckling topology optimization is artificial buckling modes in low density regions. The typical remedy applied for linear buckling does not have a natural extension to nonlinear problems, and we propose an alternative approach. Some possible negative implications of using symmetry to reduce the model size are highlighted and it is demonstrated how an initial symmetric buckling response may change to an asymmetric buckling response during the optimization process. This problem may partly be avoided by not exploiting symmetry, however special requirements are needed of the analysis method and optimization formulation. We apply a nonlinear path tracing algorithm capable of detecting different types of stability points and an optimization formulation that handles possible mode switching. This is an extension into the topology optimization realm of a method developed, and used for, fiber angle optimization in laminated composite structures. We finally discuss and pinpoint some of the issues related to buckling topology optimization that remains unsolved and demands further research.     

Infection of Brain Pericytes Underlying Neuropathology of COVID-19 Patients

A wide range of neurological manifestations have been associated with the development of COVID-19 following SARS-CoV-2 infection. However, the etiology of the neurological symptomatology is still largely unexplored. Here, we used state-of-the-art multiplexed immunostaining of human brains (n = 6 COVID-19, median age = 69.5 years; n = 7 control, median age = 68 years) and demonstrated that expression of the SARS-CoV-2 receptor ACE2 is restricted to a subset of neurovascular pericytes. Strikingly, neurological symptoms were exclusive to, and ubiquitous in, patients that exhibited moderate to high ACE2 expression in perivascular cells. Viral dsRNA was identified in the vascular wall and paralleled by perivascular inflammation, as signified by T cell and macrophage infiltration. Furthermore, fibrinogen leakage indicated compromised integrity of the blood–brain barrier. Notably, cerebrospinal fluid from additional 16 individuals (n = 8 COVID-19, median age = 67 years; n = 8 control, median age = 69.5 years) exhibited significantly lower levels of the pericyte marker PDGFRβ in SARS-CoV-2-infected cases, indicative of disrupted pericyte homeostasis. We conclude that pericyte infection by SARS-CoV-2 underlies virus entry into the privileged central nervous system space, as well as neurological symptomatology due to perivascular inflammation and a locally compromised blood–brain barrier.