Simulation and experiment of gas diffusion in a granular bed

The diffusion of gas through porous material is important to understand the physical processes underlying cometary activity. We study the diffusion of a rarefied gas (Knudsen regime) through a packed bed of monodisperse spheres via experiments and numerical modelling, providing an absolute value of the diffusion coefficient and compare it to published analytical models. The experiments are designed to be directly comparable to numerical simulations, by using precision steel beads, simple geometries, and a trade-off of the sample size between small boundary effects and efficient computation. For direct comparison, the diffusion coefficient is determined in Direct Simulation Monte Carlo (DSMC) simulations, yielding a good match with experiments. This model is further-on used on a microscopic scale, which cannot be studied in experiments, to determine the mean path of gas molecules and its distribution, and compare it against an analytical model. Scaling with sample properties (particle size, porosity) and gas properties (molecular mass, temperature) is consistent with analytical models. As predicted by these, results are very sensitive on sample porosity and we find that a tortuosity $q(\varepsilon)$ depending linearly on the porosity $\varepsilon$ can well reconcile the analytical model with experiments and simulations. Mean paths of molecules are close to those described in the literature, but their distribution deviates from the expectation for small path lengths. The provided diffusion coefficients and scaling laws are directly applicable to thermophysical models of idealised cometary material.Comment: accepted by MNRA

SNS-process monitoring in coaching. Resources of young adults in transitions. Project Kraftquellen, final report on youth and work

Das Projekt \u27Kraftquellen\u27 schreibt eine Studie, die im ‚Fachreferat Jugend und Arbeit‘ des Erzbischöflichen Jugendamtes München und Freising zwischen 2015 und 2021 durchgeführt wurde. Untersucht wurden Coachingprozesse junger Erwachsener in ihrer Veränderungsdynamik. Die Teilnehmer*innen kamen aus dem Freiwilligen Sozialen Jahr (FSJ), da diese Lebensphase zwischen Schule, Studium und/oder Ausbildung mit vielen Entscheidungen verbunden ist. Als Begleitprojekt des 2021 veröffentlichten Forschungsprojektes \u27Geduld als Ressource\u27 soll es Aufschluss darüber geben, wie junge Erwachsene in beruflich-privaten Übergängen ressourcenorientiert durch Einzelcoaching gefördert werden können. Die Coachingprozesse wurden methodisch durch das Synergetische Navigationssystem (SNS) begleitet und durch Prof. Dr. Dr. Günter Schiepek, Leiter des Institutes für Synergetik und Psychotherapieforschung von der Paracelsus Medizinischen Privatuniversität Salzburg, beraten. Basierend auf einer idiographischen Systemmodellierung wurde mit jeder/m Teilnehmer*in ein individueller Fragebogen entwickelt. Dieser wurde digital ca. 70 Tage/Teilnehmer*in bearbeitet und über ein Monitoring auf der SNS-Plattform begleitet. In den Fragebogen gingen Ressourcen des gesundheitlichen Wohlbefindens (WHO-5) und der Geduld (Studie \u27Geduld als Ressource\u27) mit ein. Die Untersuchung kommt zu dem Ergebnis, dass das Zusammenspiel der individuellen Ressourcen eine motivierende Wirkung für den Coachingprozess hat. Die Ressourcen im Feld des Wohlbefindens entsprechen dem Wunsch vieler junger Erwachsener nach Gesundheit. Die Geduld hat eine prozessstabilisierende Wirkung, sie verändert sich im zeitlichen Verlauf und im Kontext, entwickelt sich aber die die Reflektion von Geduld weiter. Insgesamt beschreiben die Coachees die Geduld als wichtige Alltagsressource. Das Projekt \u27Kraftquellen\u27 empfiehlt eine weitergehende Prozessforschung zu Coachingverläufen junger Erwachsener. (Verfasser)The Kraftquellen project is writing a study that was carried out in the \u27Fachreferat Jugend und Arbeit\u27 of the Archbishop\u27s Youth Welfare Office in Munich and Freising between 2015 and 2021. Coaching processes of young adults were examined in terms of their change dynamics. The participants came from the Voluntary Social Year (FSJ), as this phase of life between school, studies and / or training is associated with many decisions. As a companion project to the research project Patience as Resource published in May 2021 (May; Tectum Verlag), it is intended to provide information on how young adults can be promoted in a resource-oriented manner through individual coaching in professional-private transitions. The coaching processes were methodically accompanied by the Synergetic Navigation System (SNS) and by Prof. Dr. Dr. Günter Schiepek, head of the Institute for Synergetics and Psychotherapy Research at the Paracelsus Medical Private University in Salzburg. Based on an idiographic system modeling, an individual questionnaire was developed with each participant. This was processed digitally for about 70 days / participant and accompanied by monitoring on the SNS platform. In the questionnaire, resources of health well-being (WHO-5) and patience (study patience as a resource) were included. The study comes to the conclusion that the interplay of individual resources has a motivating effect on the coaching process. The resources in the field of wellbeing correspond to the desire for health of many young adults. Patience has a process-stabilizing effect, it changes over time and in context, but the reflection of patience continues to develop. Overall, the coachees describe patience as an important everyday resource. The Kraftquellen project recommends further process research on coaching courses for young adults. (Author

Observatories of the Solar Corona and Active Regions (OSCAR)

Coronal Mass Ejections (CMEs) and Corotating Interaction Regions (CIRs) are major sources of magnetic storms on Earth and are therefore considered to be the most dangerous space weather events. The Observatories of Solar Corona and Active Regions (OSCAR) mission is designed to identify the 3D structure of coronal loops and to study the trigger mechanisms of CMEs in solar Active Regions (ARs) as well as their evolution and propagation processes in the inner heliosphere. It also aims to provide monitoring and forecasting of geo- effective CMEs and CIRs. OSCAR would contribute to significant advancements in the field of solar physics, improvements of the current CME prediction models, and provide data for reliable space weather forecasting. These objectives are achieved by utilising two spacecraft with identical instrumentation, located at a heliocentric orbital distance of 1 AU from the Sun. The spacecraft will be separated by an angle of 68° to provide optimum stereoscopic view of the solar corona. We study the feasibility of such a mission and propose a preliminary design for OSCAR

Erratum: A space weather mission concept: Observatories of the solar corona and active regions (oscar) (Journal of Space Weather and Space Climate (2015) 5 (A4) DOI: 10.1051/swsc/2015003)

In this erratum we acknowledge EASCO as one of the inspirational mission concepts that helped the development of our original mission concept OSCAR

Initial results from the InSight mission on Mars

NASA’s InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in Elysium Planitia on Mars on 26 November 2018. It aims to determine the interior structure, composition and thermal state of Mars, as well as constrain present-day seismicity and impact cratering rates. Such information is key to understanding the differentiation and subsequent thermal evolution of Mars, and thus the forces that shape the planet’s surface geology and volatile processes. Here we report an overview of the first ten months of geophysical observations by InSight. As of 30 September 2019, 174 seismic events have been recorded by the lander’s seismometer, including over 20 events of moment magnitude Mw = 3–4. The detections thus far are consistent with tectonic origins, with no impact-induced seismicity yet observed, and indi- cate a seismically active planet. An assessment of these detections suggests that the frequency of global seismic events below approximately Mw = 3 is similar to that of terrestrial intraplate seismic activity, but there are fewer larger quakes; no quakes exceeding Mw = 4 have been observed. The lander’s other instruments—two cameras, atmospheric pressure, temperature and wind sensors, a magnetometer and a radiometer—have yielded much more than the intended supporting data for seismometer noise characterization: magnetic field measurements indicate a local magnetic field that is ten-times stronger than orbital estimates and meteorological measurements reveal a more dynamic atmosphere than expected, hosting baroclinic and gravity waves and convective vortices. With the mission due to last for an entire Martian year or longer, these results will be built on by further measurements by the InSight lander

Accelerometry measurements using the Rosetta Lander's anchoring harpoon: experimental set-up, data reduction and signal analysis

In the years 2011–2013 the ESA mission Rosetta will explore the short period comet 46P/Wirtanen. The aims of the mission include investigation of the physical and chemical properties of the cometary nucleus and also the evolutionary processes of comets. It is planned to land a small probe on the surface of the comet, carrying a multitude of sensors devoted to in situ investigation of the material at the landing site. On touchdown at the nucleus, an anchoring harpoon will be fired into the surface to avoid a rebound of the lander and to supply a reaction force against mechanical operations such as sample drilling or instrument platform motion. The anchor should also prevent an ejection of the lander due to gas drag from sublimating volatiles when the comet becomes more active closer to the Sun. In this paper, we report on the development of one of the sensors of the MUPUS instrument aboard the Rosetta Lander, the MUPUS ANC-M (mechanical properties) sensor. Its purpose is to measure the deceleration of the anchor harpoon during penetration into the cometary soil. First the test facilities at the Max-Planck-Institute for Extraterrestrial Physics in Garching, Germany, are briefly described. Subsequently, we analyse several accelerometer signals obtained from test shots into various target materials. A procedure for signal reduction is described and possible errors that may be superimposed on the true acceleration or deceleration of the anchor are discussed in depth, with emphasis on the occurrence of zero line offsets in the signals. Finally, the influence of high-frequency resonant oscillations of the anchor body on the signals is discussed and difficulties faced when trying to derive grain sizes of granular target materials are considered. It is concluded that with the sampling rates used in this and several other space experiments currently under way or under development a reasonable resolution of strength distribution in soil layers can be achieved, but conclusions concerning grain size distribution would probably demand much higher sampling rates

Semantic Information Retrieval in the COMPASS Location System

Abstract. In our previous work, we have described the COMPASS location system that uses multiple information sources to determine the current position of a node. The raw output of this process is a location in geo-coordinates, which is not suitable for many applications. In this paper we present an extension to COMPASS, the so called Translator, that can provide facts about the location like city name, address, room number, etc. to the application. These facts are represented in the Semantic Web RDF/XML language and stored on distributed Geo RDF Servers. The main focus of this paper is a location-based service discovery mechanism which allows a node to find all services that can provide facts about its current location. This discovery service is built upon a structured Peer-to-Peer system implementing a distributed hash table.

Impact penetrometry on a comet nucleus — interpretation of laboratory data using penetration models

The first — and possibly deepest — in situ science measurements on the 46P/Wirtanen nucleus will be made by two sensors of the Rosetta Lander's MUPUS experiment. A piezoelectric shock accelerometer (ANC-M) and a resistance temperature sensor (ANC-T) will be mounted in the Lander's harpoon anchor. This will be shot into the surface at about 60 ms−1 on touchdown, reaching a final depth of between a few centimetres and about 2.5 m, depending on the hardness of the ground and the maximum available cable length. Early indications of the strength of the surface material and any distinct layers should prove valuable to subsequent depth-sensitive investigations, including the MUPUS thermal probe, seismic sounding experiments, the sampling drill and composition analyses of the extracted material. Interpretation of the ANC-M data will help to constrain models of the formation and evolution of the material found at the landing site and document the mechanical and structural context of nearby sampled material. We report on the results of recent test shots performed with a prototype anchor into several porous materials: two types of glass foam, H2O ice and CO2 ice. With the help of data from direct shear tests and quasi-static penetration tests, we interpret the processed deceleration data using a cavity-expansion penetration model. Layers of distinctly different strengths can be detected and located, and the deceleration profiles are in reasonable agreement with the profiles obtained by quasi-static tests. The anchor projectile's long sharp tip tends to smear out the boundaries, however. In applying the penetration model we found that the coefficient of sliding friction and the target's volumetric strain have a much stronger influence on the deceleration profile than the initial target density and angle of internal friction. Very small values of volumetric strain (corresponding to high ‘drag coefficient’) were required to fit deceleration profiles to the measured data for the glass foam, contrary to what we initially expected by inspecting the thin layer of crushed material around the walls of the penetrated channel. We interpret this to mean that such brittle, porous materials as the glass foam (and perhaps highly porous, brittle, cryogenic ice) do not exhibit plastic deformation before failing completely by the crushing of cell walls. The decelerating forces are thus thought to be dominated by momentum transfer to the crushed material and by the crushing strength of the cellular microstructure, rather than by the force required to deform the target plastically. The cavity-expansion model seems to be well-suited to the ice shots, but for the brittle, cellular glass foam, alternative approaches, taking into account the material's microstructure, are needed. As a first step in this direction, a microstructural model linking textural properties of the material (pore and grain size, and relative contact area between grains) is applied to the glass foam data, obtained from quasi-static penetration tests and from direct shear strength tests. It is demonstrated that the dependence of strength on porosity can be well represented by the model suggested. A microstructural model for sintered ices, relating strength properties to porosity and thermal properties, would be useful for interpretation of MUPUS ANC-M data in the context of other physical properties measurements. The work presented here may also have some relevance to the design of future comet landers or penetrators. The harpoon anchor/penetrometer approach could be employed on other minor body landing missions, while the modelling technique is similar in many ways to that appropriate for other penetrometers/penetrators