Fork bending self-oscillation on bicycles influencing braking performance

This work deals with a fork bending oscillation phenomenon observed during hard braking on bicycles. The observed oscillation is described with experimental data and an attempt is made to understand the underlying root cause. Therefore, a multibody model consisting of the front wheel and the fork is employed to simulate a braking maneuver. The self-oscillation is replicated in simulation and implications on the brake process are derived from it. Fork and tire oscillations on bicycles are rarely described in scientific literature. An oscillation due to tire resonance on high-speed motorcycles was described by Cossalter [1]. However, the mentioned speed dependence is not found in the present case under investigation. Klug et al. [2] were the first to report an oscillation of the fork inclination angle during braking. They noticed oscillations in the front wheel speed signals measured with a speed encoder mounted on the fork. Measurements of accelerometers and gyroscopes placed on the fork near the hub showed these oscillations on the forks inclination angular rate and vertical acceleration as well. This makes the phenomenon relevant for suspension and braking control. They also described the distorting effect of fork bending on the wheel speed signal and the wheel slip calculation derived from it. This work tries to identify a root cause of the fork bending oscillation and investigates its influence on the stopping performance

Investigating thermally activated deformation mechanisms by high temperature nanoindentation – A Study on W-Re alloys

Since the advent of indentation at elevated temperatures the technique of high-temperature nanoindentation has been further developed, currently enabling testing temperatures above 1000 °C. Due to small sample sizes and a variety of different testing techniques this method provides the opportunity for alloy development at a new level regarding composition variety or efficiency. In this study the thermally activated deformation mechanisms in binary W-Re alloys will be investigated by using a high-end in-situ nanoindenter. For that purpose, three different materials were tested, namely commercially pure W, W5Re and W10Re, all of them in both, coarse grained and ultra-fine grained condition. Nanoindentation experiments were conducted from ambient temperatures up to 800 °C, thereby overcoming the critical temperature TC of tungsten at around 450 °C. With temperature increments of 100 °C a large range of the normalized temperature with respect to TC is covered, allowing general conclusions regarding the appearing deformation mechanisms in bcc metals. Additionally to constant indentation strain rate tests, strain rate jump tests were utilized to determine the mechanical properties and to evaluate the impact of temperature and microstructure on rate-dependent parameters. A strong influence of the alloying level with Re as well as the grain size on both, the thermal and athermal contribution to the flow stress, is observed. The origin and effects, such as solid solution softening for W5Re at temperatures far below TC, will be discussed in detail. Furthermore, the dominating deformation mechanisms in dependence of temperature and grain size are determined. In the coarse grained materials a change in deformation processes from kink-pair mechanism to dislocation-dislocation interaction at higher temperatures can be observed, while in ultra-fine grained materials grain boundary/dislocation interactions are responsible for the maintained time-dependent mechanical behavior

Phase transformations and local deformation mechanisms - A case study on Cu 20 m.% Sn

Please click Additional Files below to see the full abstract

Robotic intra-row weed hoeing in maize and sugar beet

A prototype of robotic intra-row weed hoeing in maize and sugar beet is presented in this study. Weeds in the crop rows were identified using a bi-spectral image analysis system and shape analysis. Positions of weeds in the images were recorded. Selective weed control in the row was performed with a modified finger weeder driven by electrical motors. Speed of the finger weeder was increased at positions where only weeds were classified. The system was triggered by an encoder and controlled by a micro-controller. Roboter-gesteuerte Unkrauthacke in der Reihe von Mais und ZuckerrübenEin Prototyp einer roboter-gesteuerten Hacke zur Unkrautbekämpfung in den Reihen von Mais und Zuckerrübe wird in dieser Studie vorgestellt. Unkräuter und Kulturpflanzen wurden mit einer bi-spektralen Kamera und Formenanalyse erkannt. Die Positionen der Unkräuter im Bild wurden bestimmt. Die selektive Unkrautbekämpfung in der Reihe geschah mit einer modifizierten Fingerhacke, die über Elektromotoren angetrieben werden. Die Fingerhacke wurde beschleunigt, wenn nur Unkräuter in der Reihe klassifiziert wurden. Das System wurde mit einem Inkrementalgeber getriggert und über einen Micro-Controller gesteuert

Social acceptance of green hydrogen in Germany: building trust through responsible innovation

Background Social acceptance presents a major challenge for Germany’s transition to green energy. As a power-to-x technology, green hydrogen is set to become a key component of a future sustainable energy system. With a view to averting conflicts like those surrounding wind energy, we have investigated social acceptance of green hydrogen at an early stage in its implementation, before wider rollout. Our study uses a mixed-method approach, wherein semi-structured interviews (n = 24) and two participatory workshops (n = 51) in a selected region in central Germany serve alongside a representative survey (n = 2054) as the basis for both understanding social attitudes and reaching generalisable conclusions. Results Overall, it is possible to observe both a marked lack of knowledge and a large degree of openness towards green hydrogen and its local use, along with high expectations regarding environmental and climate protection. We reach three key conclusions. First, acceptance of green hydrogen relies on trust in science, government, the media, and institutions that uphold distributive justice, with consideration for regional values playing a vital role in establishing said trust. Second, methodologically sound participatory processes can promote acceptance, and active support in particular. Third, recurrent positive participatory experiences can effectively foster trust. Conclusions Accordingly, we argue that trust should be strengthened on a structural level, and that green hydrogen acceptance should be understood as a matter of responsible innovation. As the first empirical investigation into social acceptance of green hydrogen, and by conceptually interlinking acceptance research and responsible innovation, this study constitutes an important contribution to existing research

Navigated interventions in the head and neck area: standardized assessment of a new handy field generator

Electromagnetic (EM) tracking enables localization of surgical instruments within the magnetic field emitted by an EM field generator (FG). Usually, the larger a FG is, the larger its tracking volume is. However, the company NDI (Northern Digital Inc., Waterloo, ON, Canada) recently introduced the Planar 10-11 FG, which combines a compact construction (97mm x 112mm x 31mm) with a relatively large, cylindrical tracking volume (diameter: 340mm, height: 340mm). Using the standardized assessment protocol of Hummel et al., the FG was tested with regard to its tracking accuracy and to its robustness with respect to external sources of disturbance. The mean positional error (5cm distance metric according to Hummel protocol) was 0.59mm, with a mean jitter of 0.26mm in the standard setup. The mean orientational error was found to be 0.10{\deg}. The highest positional error (4.82mm) due to metallic sources of disturbance was caused by the steel SST 303. In contrast, steel SST 416 caused the lowest positional error (0.10mm). Overall, the Planar 10-11 FG tends to achieve better tracking accuracy results compared to other NDI FGs. Due to its compact construction and portability, the FG could contribute to increased clinical use of EM tracking systems.Comment: This is the preprint version of the BVM paper already published in the conference proceedings of "Bildverarbeitung in der Medizin 2019". Paper written in Germa

Einfluss der unterschiedlichen Komposte auf Erträge unter Praxisbedingungen

Wirkungen unterschiedlicher Komposte und Aufwandmengen in ökologischen Fruchtfolgen auf Ertrag und Produktqualität, Bodenprozesse und Umwelt werden in einem randomisierten Feldversuch und in drei Streifenversuchen in landwirtschaftlichen Betrieben mit praxisüblicher Technik durchgeführt

ERP hoch 3: Energieraumplanung entlang von ÖV-Achsen

Im Rahmen des national geförderten Forschungsprojekt „ERP_hoch3“ wird der Themenschwerpunkt Energieraumplanung in drei Fokusebenen betrachtet, untersucht und simuliert. Während „ERP“ für Energieraum-planung steht, steht die „3“ für drei verschiedene Raumbezüge – Stadtquartiere, öffentliche Verkehrsachsen und interkommunale Flächenpotenziale erneuerbarer Energien (Region). ERP_hoch3 ist ein zweijähriges Grundlagenforschungsprojekt, gefördert vom österreichischen Klimafonds. Das Forschungsteam besteht aus 14 Expertinnen und Experten der Fachbereiche für Regionalplanung und für örtliche Raumplanung (TU Wien, Department für Raumplanung) und der Institute für Städtebau und Prozess- und Partikeltechnik (TU Graz)

Effects of ocean biology on the penetrative radiation in a coupled climate model

The influence of phytoplankton on the seasonal cycle and the mean global climate is investigated in a fully coupled climate model. The control experiment uses a fixed attenuation depth for shortwave radiation, while the attenuation depth in the experiment with biology is derived from phytoplankton concentrations simulated with a marine biogeochemical model coupled online to the ocean model. Some of the changes in the upper ocean are similar to the results from previous studies that did not use interactive atmospheres, for example, amplification of the seasonal cycle; warming in upwelling regions, such as the equatorial Pacific and the Arabian Sea; and reduction in sea ice cover in the high latitudes. In addition, positive feedbacks within the climate system cause a global shift of the seasonal cycle. The onset of spring is about 2 weeks earlier, which results in a more realistic representation of the seasons. Feedback mechanisms, such as increased wind stress and changes in the shortwave radiation, lead to significant warming in the midlatitudes in summer and to seasonal modifications of the overall warming in the equatorial Pacific. Temperature changes also occur over land where they are sometimes even larger than over the ocean. In the equatorial Pacific, the strength of interannual SST variability is reduced by about 10%–15% and phase locking to the annual cycle is improved. The ENSO spectral peak is broader than in the experiment without biology and the dominant ENSO period is increased to around 5 yr. Also the skewness of ENSO variability is slightly improved. All of these changes lead to the conclusion that the influence of marine biology on the radiative budget of the upper ocean should be considered in detailed simulations of the earth’s climate