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Despite growing environmental concern, combustion engines are projected to stay the main technology of transportation for many years, so will unpopular S- and P- containing additives in lubricating oils. Therefore, it is essential to maximize efficiency and minimize the harmful impacts of these additives in the meantime. Coatings based on Mo and W hold great promise as they can chemically interact with S-bearing additives and form low friction tribofilms like MoS2 and in particular WS2. Here we highlight the reaction pathways involving first the formation of oxide intermediates, followed by the generation of a highly protective and low-shear transition metal disulfide tribofilm on a tailored WN-based coating, affording coefficients of friction as low as 0.05 combined with an extraordinary wear protection (i.e., no measurable wear on sliding surfaces even after 100 h of testing). High resolution TEM and Raman spectroscopy confirm the formation of WS2 sheets and hence the huge potential of these coatings for lubricated surfaces. Keywords: In-situ WS2, Coating-lubricant interaction, Tungsten nitride, Thin film, Tribofilm

Single-screw extruders are usually operated with the screw fully filled (flood-fed mode) and not partially filled (starve-fed mode). These modes result in completely different processing characteristics, and although starve-fed mode has been shown to have significant advantages, such as improved mixing and melting performance, it is rarely used, and experimental studies are scarce. Here, we present extensive experimental research into starve-fed extrusion at feeding rates as low as 25%. We compared various operating parameters (e.g., residence time, pressure build-up, and melting performance) at various feeding rates and screw speeds. The results show a first insight into the performance of starve-fed extruders compared to flood-fed extruders. We explored starve-fed extrusion of a polyethylene material which contains a Very High Molecular Weight Polyethylene fraction (VHMWPE). VHMWPE offers several advantages in terms of mechanical properties, but its high viscosity renders common continuous melt processes, such as compression molding, ram extrusion and sintering, ineffective. This work shows that operating single-screw extruders in extreme starve-fed mode significantly increases residence time, melt temperature, and improves melting and that-in combination—this results in significant elongation of VHMWPE particles.

Glass flexural resonators have established themselves as one of the de-facto standard methods for measuring the density of liquids in a laboratory environment. The core of this sensor is a U-Tube measuring cell whose oscillator’s resonance frequency changes with the mass of the liquid within the tube. This relationship can be used to derive the density of liquids in a fast and reliable way. In order to achieve the highest accuracy for the density measurement multiple physical effects (e.g., damping due to viscosity effects) need to be taken into account. For a reliable correction, additional measurements are required. The pulsed excitation method is able to produce these additional parameters along with a superior measurement performance compared to previous techniques.

Nature Communications 5: Article number: 3524 (2014); Published 8 April 2014; Updated 29 March 2018 The original HTML version of this Article had an incorrect article number of 3424; it should have been 3524. This has now been corrected in the HTML; the PDF version of the Article was correct from the time of publication.

Active upper limb prostheses can be controlled by surface electromyography (EMG) signals. State of the art sensors are based on conductive electrodes which measure local voltage differences at the surface of the skin due to muscle activity. The current project deals with non-conductive measurement of EMG signals. For this purpose a sensor was designed as multi-layered composite of conducting and insolating materials. The different layers were used for signal sensing as well as active and passive guarding. The low amplitude EMG signal was detected by differential capacitive sensors. Electronic circuits were developed for the special requirements of these capacitive sensors. Basic requirements were high input impedance, high amplification and filters, e.g. for suppression of power supply hum and its harmonics. For the differential signal high common mode rejection ratio is essential. The electronics comprise rectification and smoothing of the output signal. A standard prosthesis is controlled successfully with the prototype output signal. When placing the sensors on the human forearm, the prosthesis follows the desired hand movement. [ABSTRACT FROM AUTHOR]