CANEUS2006-11042 HIGH TEMPERATURE (800°C) MEMS PRESSURE SENSOR DEVELOPMENT INCLUDING REUSABLE PACKAGING FOR ROCKET ENGINE APPLICATIONS

ABSTRACT For aircraft and rocket engines there is a strong need to measure the pressure in the propulsion system at high temperature (HT) with a high local resolution. Miniaturized sensor elements commercially available show decisive disadvantages. With piezoelectric-based sensors working clearly above 500°C static pressures can not be measured. Optical sensors are very expensive and require complex electronics. SiC sensor prototypes are operated up to 650°C, but require high technological efforts. The present approach is based on resistors placed on top of a 2 mm diameter sapphire membrane (8 mm chip diameter). The strain gauges are made either of antimony doped tin oxide (SnO2:Sb) or platinum (Pt). This material combination allows for matching the thermal coefficients of expansion (TCE) of the materials involved. The morphology of the SnO 2 :Sb layer can be optimized to reduce surface roughness on the nanometer scale and hence, gas sensitivity. Antimony doping increases conductivity, but decreases the gauge factor. With this nanotechnological knowledge it is possible to adjust the material properties to the needs of our aerospace applications. Tin oxide was shown to be very stable at HT. We also measured a 2.5% change in electrica

Roadmap on holography

From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful.This work was supported by Ministerio de Economía, Industria y Competitividad (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER), and by Generalitat Valenciana (Spain) under project PROMETEO II/2015/015

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Modeling Enhanced Performances by Optical Nanostructures in Water-Splitting Photoelectrodes

Material nanostructuring and optical phenomena on a nanoscale such as plasmonic effects and light scattering have been widely studied for improving the solar-to-hydrogen efficiency of photoelectrochemical (PEC) water-splitting electrodes. In this work, we report a method for analyzing the contributions of optical effects from nanostructures for enhancing the PEC performances. Electromagnetic simulations are performed for the precise calculation of generated power density in a semiconductor material. In addition, the transport and transfer of photogenerated charges to the electrolyte are modeled by using the conservation of minority carriers. The surface loss parameter, diffusion length, and doping density of the semiconductor material are determined by fitting the model to an incident photon to current efficiency (IPCE) curve experimentally measured on the bare reference photoelectrode. These parameters are then used to compute the IPCE spectra of the photoelectrode for which an optical enhancement strategy is used, such as nanostructuring or plasmonics. The method is validated using published experimental data. The calculated IPCE enhancement ratio originating from optical effects is in quantitative agreement with experimental observations for both periodic and random optical structures. The model can be used to study in detail the key enhancement mechanisms for the IPCE from optical nanostructures and, in particular, discriminate between optical and nonoptical (e.g., catalytic) enhancement

Fatigue strength of fillet-welded joints at subzero temperatures

Ships and offshore structures may be operated in areas with seasonal freezing temperatures and extreme environmental conditions. While current standards state that attention should be given to the validity of fatigue design curves at subzero temperatures, studies on fatigue strength of structural steel at subzero temperatures are scarce. This study addresses the issue by analysing the fatigue strength of welded steel joints under subzero temperatures. Although critical weld details in large welded structures are mostly fillet-welded joints, most published data are based on fatigue crack growth rate specimens cut out of butt-welded joints. This study analyses fillet-welded specimens at −20°C and −50°C against controls at room temperature. Significantly higher fatigue strength was measured in comparison to estimates based on international standards and data from design codes even at temperatures far below the allowed service temperature based on fracture toughness results.German Research AssociationDonors' Association for the Promotion of Sciences and Humanities in German

A Sampling-Based Ratio Bridge for Calibrating Voltage Transformers

This paper describes the setup of a sampling-based ratio bridge for calibrating voltage transformers. The advantage of this ratio method is that voltage transformers with different transformer ratios can be easily compared. Initial measurements of the components of the bridge indicate low systematic errors, negligible voltage dependency and low phase errors around 50 / 60 Hz. This indicates an attainable uncertainty of below 2 ppm for the ratio error and \pmb0.5 μ rad for the phase displacement of voltage transformers

Requirements for stress gradient-based fatigue assessment of notched structures according to theory of critical distance

Notches, local stress raisers within structural components, are one of the most important locations for fatigue crack initiation. It is well known that fatigue is governed by the effective stresses in the vicinity of notches. Within this study, differences in prediction accuracy between different types of theory of critical distance methods, that is, point and line methods, are systematically investigated in conjunction with a sensitivity study regarding mesh refinement, assumed strength hypothesis and material behaviour. For this purpose, a finite element analysis parameter study on notched structures is performed and recommendations for the application of stress gradient methods are presented. Difference in effective stress of up to 30%, and hence a significant difference in fatigue life (e.g., 185% for a slope of S-N curve of k = 4), is found for typical notch shapes, for example, in welded joints.The work was performed within the research project ESM-50 ‘Fatigue of welded structures at sub-zero temperatures’, funded by the German Research Association of the Working Group of the Iron- and Metal-processing Industry e.V. as part of the Donors' Association for the Promotion of Sciences and Humanities in Germany under project number AVIF-No. A301

Grading mit Grappa - Ein Werkstattbericht

„Grappa“ ist eine Middleware, die auf die Anbindung verschiedener Autobewerter an verschiedene E-Learning-Frontends respektive Lernmanagementsysteme (LMS) spezialisiert ist. Ein Prototyp befindet sich seit mehreren Semestern an der Hochschule Hannover mit dem LMS „moodle“ und dem Backend „aSQLg“ im Einsatz und wird regelmäßig evaluiert. Dieser Beitrag stellt den aktuellen Entwicklungsstand von Grappa nach diversen Neu- und Weiterentwicklungen vor. Nach einem Bericht über zuletzt gesammelte Erfahrungen mit der genannten Kombination von Systemen stellen wir wesentliche Neuerungen der moodle-Plugins, welche der Steuerung von Grappa aus moodle heraus dienen, vor. Anschließend stellen wir eine Erweiterung der bisherigen Architektur in Form eines neuentwickelten Grappa-php-Clients zur effizienteren Anbindung von LMS vor. Weiterhin berichten wir über die Anbindung eines weiteren Autobewerters „Graja“ für Programmieraufgaben in Java. Der Bericht zeigt, dass bereits wichtige Schritte für eine einheitliche Darstellung automatisierter Programmbewertung in LMS mit unterschiedlichen Autobewertern für die Studierenden absolviert sind. Die praktischen Erfahrungen zeigen aber auch, dass sowohl bei jeder der Systemkomponenten individuell, wie auch in deren Zusammenspiel via Grappa noch weitere Entwicklungsarbeiten erforderlich sind, um die Akzeptanz und Nutzung bei Studierenden sowie Lehrenden weiter zu steigern

Influence of the optical measurement technique and evaluation approach on the determination of local weld geometry parameters for different weld types

The joining by welding processes of components is usually related to the creation of additional notches and geometrical peculiarities. Multiple investigations have shown that a clear correlation between the local weld geometry and the fatigue life of welded joints exist. Thereby, the local increase of the local stress can be expressed by a stress concentration factor at the transition from the base material to the filler material, the so-called weld toe. The stress concentration factor can be determined for the most weld types if the geometric parameters such as plate thickness weld toe radius and flank angle are known. However, no standardized method for the determination of these parameters exists. Beside the well-established 2D-measurement methods on cross sections with weld impression analysis, new 3D-methods based on contactless, optical measurement were applied in the last years for the geometrical analysis of welded joints. With these methods, long length of welds can be analyzed in a very short time and with low effort. However, the influence of the measurement system (geometrical accuracy, lateral resolution) was not quantified yet. Additionally, in all known cases of application different evaluation algorithms were used. This does not allow for a straightforward comparison of the investigated parameters and results. In this round robin study, the determination of weld toe radii and flank angles by different evaluation algorithms and 3D-measurement systems and by different institutes are compared. Furthermore, an approach for the direct determination of the stress concentration factors of fillet welds by translating the complex weld shape in a 2D-finite element simulation was implemented. The results of this direct approach are compared to the stress concentration factors determined indirectly using the geometric parameters and those calculated by established approximation formulas