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Improved Dynamic Behaviour of Industrial Robots through Hybrid Drives
No full text390397The objective of this work is to evaluate the accuracy of an industrial robot with hybrid drives for improved dynamic path accuracy and productivity. The dynamic behaviour of industrial robots is profoundly influenced by the drives characteristics in the robot’s joints. For customary industrial robots, the transmission of movement from the motor to the axis link via a gearbox causes inaccuracies along the kinematic chain. To address this context, this work investigates the hybrid drives influence on the dynamic behaviour of a novel industrial robot. Therefore, additional torque drives compensate for errors arising from the limited torsional stiffness of the gearbox. The experimental results on a novel industrial robot underlines the enhancement of dynamic path accuracy and productivity of industrial robots with the presented drive concept
Parameters affecting the pozzolanic reactivity of common clays after mechanochemical activation
No full textMechanochemical activation (MCA) of phyllosilicates is one of the most promising solutions to produce reactive supplementary cementitious materials (SCMs). Several studies have already shown that MCA outperforms thermal activation (TA) in terms of reactivity when clays are low in kaolinite but rich in 2:1 phyllosilicates. Because reactivity depends on phyllosilicate type as well as content, and clays vary widely, a quick and simple test is needed to assess raw material suitability. Therefore, the aim of this study was to investigate the mineralogical and physical properties of common clays and their impact on reactivity after MCA, as well as their suitability as SCM. Hence, a multi-method approach was used to determine the reactivity of seven German common clays after TA and MCA and their use as SCM. The R3-test was used to determine the evolved heat after 7 days. Thermal analysis showed an altered OH binding that went along with a decrease in surface area with prolonged milling. Through Rietveld refinement of the X-ray diffraction analysis and the external standard method, the amorphous content of the phyllosilicates was determined. An increase in the amorphous content was observed after MCA. The solubility of Al and Si could also be correlated with the reactivity of the phyllosilicates. The concentration of all ions increased with prolonged milling time, and therefore also correlated linearly with the reactivity. Both the loss of dehydroxylation area and the Si:Al solubility ratio served as practical, rapid screening tools for raw-material suitability.28
Das Onboarding in Unternehmen wirksam gestalten
No full textOnboarding ist ein zentraler Bestandteil der Employee Journey und ein wesentlicher Erfolgsfaktor für Motivation, Bindung und Leistungsfähigkeit neuer Mitarbeitender. Das Whitepaper betrachtet Onboarding als ganzheitlichen Prozess, der sachlogische und psychologische Dimensionen verbindet. Im Fokus stehen Generationenmanagement, Wissenstransfer und Führung als zentrale Gestaltungsfelder. Ergänzend wird mit dem Transformations- und Innovationsnavigator (TIN) ein praxisnahes Instrument vorgestellt, das Onboarding als strategischen Hebel organisationaler Transformation unterstützt
LTCC-based Ceramic Substrates for Identification of Trustworthy Electronics
No full text216218The technology of low temperature cofired ceramics (LTCC) is already established in the production of reliable and robust electronic assemblies (e.g., multi-chip modules, system-in-package) as well as in safety-critical areas. With the incorporation of additional features based on surface profiles modular protection functions and barriers will be developed as a contribution to trustworthy electronics. Both obvious and hidden structures are investigated in a modular way, which in combination ensures a one-to-one tamper-proof identification. Keywords — trustworthy electronics, obvious and hidden structures, embossing, LTC
Strukturelle Stahlklebungen: Aufgeklebte Profile zur Versteifung großflächiger Bauteile in maritimen Strukturen
No full text1619Im FSM-Projekt KlebProfi haben das Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung IFAM in Bremen und das Karlsruher Institut für Technologie - KIT Stahl- und Leichtbau eine Methode zur Applikation geklebter Steifenprofile auf flächigen Bauteilen maritimer Strukturen entwickelt und validiert. Durch den gezielten Einsatz der Klebtechnik können negative Folgen der konventionellen schweißtechnischen Fertigung reduziert und der Fertigungsablauf optimiert werden.780
Millimeter-Wave High-Efficiency Doherty Power Amplifiers in Gallium Nitride High-Electron-Mobility Transistor Technology
No full textThe global demand for high data rates is pushing wireless systems into the millimeter-wave (mm-wave) band, where broader spectrum bandwidths can unlock the potential of 5G and future 6G. However, this shift creates a critical efficiency challenge for the power amplifiers that form the heart of base stations. This work addresses the urgent need for energy-efficient amplification to ensure sustainable, high-performance next-generation networks.
This dissertation presents a comprehensive advancement in the design of high-efficiency Doherty Power Amplifiers (DPAs) using Gallium Nitride (GaN) technology for mm-wave applications. It introduces innovative solutions to the key limitations of efficiency, bandwidth, and gain. Through novel harmonic-tuning networks and second-harmonic injection techniques, the research delivers state-of-the-art prototypes. Demonstrators like the SAFI DPA achieve record-breaking performance, covering crucial 5G bands with exceptional power-added efficiency and circuit bandwidth. The work establishes a foundational design framework, paving the way for energy-efficient mm-wave transmitters that reduce operational costs and environmental impact
Electrospinning of a bacteriophage-releasing material with antibacterial properties against S.aureus
No full textStaphylococcus aureus causes infections of topical and surgical wounds that may be difficult to treat due to drug-resistance. Much research effort is focused on overcoming this health problem. Bacteriophages could be an option for the treatment of antibiotic-resistant bacterial strains because phages target pathogenic strains with high specificity without affecting the human microbiome. However, the main problem is to incorporate phages in a proper support. In this study, a S. aureus -targeting phage was integrated into polycaprolactone/polyethylene glycol coaxial fibers by electrospinning. The characterization of the physicochemical and mechanical properties of the electrospun materials showed no significant differences in morphology, Young's modulus (∼10 MPa) and tensile strength between the fibers with and without phages. In degradation tests, electrospun fibers with and without phages exhibited the same stability and in aqueous solution, both lost 50 % of their mass (i.e. the PEG component). The lytic activity against S. aureus of the phages incorporated in the electrospun fibers was confirmed in vitro and decreased by 50 % after 30-day storage at 4 °C. Altogether, this proof-of-principle study indicates that phage incorporation into coaxial electrospun fibers represents a promising approach to generate biomaterial with antibacterial properties.11
The heart knows best: baseline heart rate variability as guide to transcutaneous auricular vagus nerve stimulation in depression
No full textMajor Depressive Disorder can be conceptualized as a chronic stress condition associated with autonomic dysregulation, including blunted heart rate reactivity, elevated basal cortisol levels and higher low-grade peripheral inflammation, pointing to an autonomic imbalance with relative sympathetic overactivation and parasympathetic attenuation. Transcutaneous vagus nerve stimulation (taVNS) offers a non-invasive method to stimulate the vagus nerve, as key component of the parasympathetic system, to restore autonomic balance. Here, we examined whether emotional (i.e., positive and negative emotions), cardiac (i.e., heart rate and heart rate variability (HRV)), and inflammatory (i.e., TNF- α, IL-6) reactivity to stress are differentially influenced by taVNS in participants with MDD and controls. Additionally, we performed a post-hoc analysis with participants stratified by baseline RMSSD, as a proxy for vagus nerve activity, to evaluate the utility of biological stratification beyond diagnostic criteria. To assess the effect of chronic stress we conducted a single-blinded, cross-over, randomized controlled trial with 110 participants (51 controls and 59 MDD participants). For the analysis stratified by RMSSD group, we grouped participants into low (n = 54) vs. high (n = 55) RMSSD groups, regardless of diagnosis. All participants were subjected to an acute stress paradigm, both with taVNS and sham stimulation on two separate days, in a counter-balanced order. There was no difference in any of the outcomes regarding the effect of taVNS in participants with MDD and controls. Analyses split by RMSSD group, however, showed that for those with low RMSSD, taVNS restored the blunted cardiac stress response and numerically decreased TNF-α levels. Unexpectedly, in participants with high RMSSD, the opposite pattern was observed: heart rate and TNF-α were significantly increased, and vagally mediated heart rate variability was significantly decreased under taVNS compared to sham stimulation. Analyses using RMSSD as continuous predictor yielded similar results. Our findings suggest that RMSSD-based stratification may be a useful tool for predicting outcome of (ta)VNS treatment. We encourage researchers with HRV data to re-evaluate their findings through RMSSD stratification.15
Potential of Robot-Guided Centrifugal Disc Finishing
No full text283291Centrifugal disc finishing is a free abrasive grinding process characterised by high material removal rates compared to the widely used vibratory finishing. The process is used for deburring and surface polishing of workpieces. In conventional unguided centrifugal disc finishing, the workpieces are machined freely movable within a bulk of flowing abrasive media. In this study, the robot-guided centrifugal disc finishing is presented in which the workpieces are guided by an industrial robot. Based on finishing experiments, it is found that the material removal rate of robot-guided centrifugal disc finishing is significant higher compared to unguided centrifugal disc finishing. Therefore, robot-guided centrifugal disc finishing can be used for time efficient deburring and surface finishing operations. Furthermore, a material removal model based on the discrete element method is presented. The model is valid for both, unguided and robot-guided centrifugal disc finishing. Thus, the model can be used as a universal tool to design centrifugal disc finishing processes without using a time and cost intensive trial and error approach.Part F116
Facile Synthesis of Gram-Scale Mesoporous Ag/TiO2 Photocatalysts for Pharmaceutical Water Pollutant Removal and Green Hydrogen Generation
No full text12491261This work demonstrates a two-step gram-scale synthesis of presynthesized silver (Ag) nanoparticles impregnated with mesoporo us TiO2 and evaluates their feasibility for wastewater treatment and hydrogen gas generation under natural sunlight. Paracetamol was chosen as the model pharmaceutical pollutant for evaluating photocatalytic performance. A systematic material analysis (morphology, chemical environment, optical bandgap energy) of the Ag/TiO2 photocatalyst powder was carried out, and the influence of material properties on the performance is discussed in detail. The experimental results showed that the decoration of anatase TiO2 nanoparticles (size between 80 and 100 nm) with 5 nm Ag nanoparticles (1 wt %) induced visible-light absorption and enhanced charge carrier separation. As a result, 0.01 g/L Ag/TiO2 effectively removed 99% of 0.01 g/L paracetamol in 120 min and exhibited 60% higher photocatalytic removal than pristine TiO2. Alongside paracetamol degradation, Ag/TiO2 led to the generation of 1729 ìmol H2 g-1 h-1. This proof-of-concept approach for tandem pollutant degradation and hydrogen generation was further evaluated with rare earth metal (lanthanum)- and nonmetal (nitrogen)-doped TiO2, which also showed a positive response. Using a combination of ab initio calculations and our new theory model, we revealed that the enhanced photocatalytic performance of Ag/TiO2 was due to the surface Fermi-level change of TiO2 and lowered surface reaction energy barrier for water pollutant oxidation. This work opens new opportunities for exploiting tandem photocatalytic routes beyond water splitting and understanding the simultaneous reactions in metal-doped metal oxide photocatalyst systems under natural sunlight.8