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Early metakaolin reactions in pozzolanic R³-test: calorimetry baseline correction of initial temperature jump due to ex-situ mixing
No full textThe increasing concerns regarding global warming and the scarcity of raw materials in the construction industry have led to a growing need for alternative low-carbon binders to partially replace ordinary Portland cement. To assess the suitability of pozzolans as supplementary cementitious materials (SCMs), the R³-test has been introduced and successfully validated for a wide range of materials. This test provides an opportunity to analyze the reactivity classification and study the reaction mechanisms and kinetics of novel SCMs in a well-controlled environment. In this study, the focus lies on evaluating the early reactions of lime paste samples through isothermal calorimetry tests conducted at 40 °C. However, conventional mixing methods present experimental challenges. In-situ mixing fails to achieve proper paste homogenization, while ex-situ mixing results in a temperature difference at the start of testing due to the elevated testing condition of 40 °C. To address these concerns, a novel calorimetric methodology is proposed for early detection of reactivity responses. The main concept involves establishing a baseline correction for the temperature difference caused by ex-situ mixing, which is calibrated using an inert sample. This correction allows for the extraction of the heat generated by the early reactions. Combined with the Tian time correction, this methodology enables the evaluation of early reactions in lime paste samples measured with isothermal calorimetry at 40 °C within the first 100 min after mixing. The effectiveness of this methodology was demonstrated by evaluating the early reactions and the impact of potassium sulfate on three different types of metakaolin
Determination of the bending strength of glass via four point bending: correction of factor kₑ in EN1288-3
Get PDFEN1288-3 (Glass in building—Determination of the bending strength of glass—Part 3: test with specimen supported at two points (four point bending), 2000) describes the four point bending test for the determination of glass strength. The failure stress is calculated from the vertical force of the testing machine. To determine the difference between the stress calculated from linear 1st order theory and actual glass stress, a factor kₑ is given. This factor is derived from a 1994 publication (Blank in Glass Sci Technol 67:9–15, 1994) that uses a very simplified finite element model. The present paper will show that for tests with high deformation, which becomes more relevant for smaller glass thickness and chemically strengthened glass, these results differ vastly from the actual behaviour of the glass in the four point bending test as it is performed in most industry and lab settings. With the corrected curves for kₑ, increases in the characteristic edge strength of more than 50% compared to the current version of EN1288-3 can be derived from the four point bending test in some cases
Challenges for Cyber Arms Control: A Qualitative Expert Interview Study
No full textThe militarization of cyberspace has been a topic in international fora and scientific debates for several years. However, the development of applicable, and verifiable arms control measures that can effectively reduce the risk of military escalations in cyberspace is still hindered by the characteristics of this domain. The article analyses challenges and obstacles of dual-use, proliferation, constant technological progress, the importance of the private sector, difficulties in defining and verifying weapons and difficulties in attributing attacks
Engel, Sonja/Schrage, Dominik: Das Spießerverdikt. Invektiven gegen die Mittelmäßigkeit der Mitte im 19. Jahrhundert, 228 S., transcript, Bielefeld 2022.
No full textSonja Engel und Dominik Schrage haben mit ihrer Studie über das „Spießerverdikt“ eine in der Tat interessante Ergänzung zur Forschung über die „Mittelmäßigkeit der Mitte im 19. Jahrhundert“ vorgelegt, wie es im Untertitel der Publikation heißt. Das Buch möchte einen wissenssoziologischen Deutungsansatz anbieten, der aktuelle Diskussionen um Spießertum ebenso zu kontextualisieren vermag, wie es soziologische Fachdebatten zur Mittelschichtsforschung anreichern kann
Applications of Transitiometry: Determination of Thermophysical Properties and Decomposition Kinetics of Peroxide(Mixtures) Under High-Pressure
No full textScanning transitiometry is an important calorimetric method co-invented by Jean-Pierre E. Grolier and Stanisław L. Randzio. Transitiometry enables to measure highly sensitive under high-pressure and high-temperature conditions. Nowadays, process modelling is a tool of increasing importance beyond the process of understanding process dynamics. For a valid modelling approach, a reliable data base at process conditions is required. Many processes are carried out at high temperature and pressure. Under such harsh conditions, comparatively few methods can be applied and thus limited kinetic parameters are known. Therefore, extrapolated values from low-pressure data are often utilized. Transitiometry can reduce this data gap for thermophysical properties such as heat capacity, thermal expansion coefficient and isothermal compressibility. In this paper, an overview about the method evaluation to determine thermophysical properties under high pressure using transitiometry is given. Additionally, an oversight is provided of the investigation of the decomposition kinetics of peroxides and their mixtures as another application area of high-pressure calorimetry
Virtual field trips in hydrological field laboratories: The potential of virtual reality for conveying hydrological engineering content
No full textWith the start of the COVID-19 pandemic and the resulting contact restrictions, conducting field trips to hydrological research basins became close to impossible. Hydrological field knowledge is an essential part of hydrological education and research. In order to impart this knowledge to students of hydrological engineering subjects in times or situations where on-site exploration is not possible, the VR4Hydro tool was developed. VR4Hydro is a virtual reality platform built from 360° panoramas that allows users to interactively explore the Gersprenz River basin in Germany. The following study seeks to investigate the applicability of performing virtual field trips in the context of hydrological education by evaluating user experience. Sixteen students of the subject engineering hydrology were asked to document their experiences with VR4Hydro using a qualitative approach by answering a series of multiple-choice questions as well as long-answer text questions. The analysis and discussion of the results showed that virtual excursions generally met with great interest among users. The majority rated the virtual tour as a valuable addition to traditional teaching methods. All students found the tool particularly appealing in cases where external circumstances did not allow for a real excursion. The findings of this study show that the application of virtual field trips (VFT) in hydrological engineering can be a valuable supplement to real field trips to improve the interest and learning outcome of students
Modelling and predicting enterprise-level cyber risks in the context of sparse data availability
No full textDespite growing attention to cyber risks in research and practice, quantitative cyber risk assessments remain limited, mainly due to a lack of reliable data. This analysis leverages sparse historical data to quantify the financial impact of cyber incidents at the enterprise level. For this purpose, an operational risk database—which has not been previously used in cyber research—was examined to model and predict the likelihood, severity and time dependence of a company’s cyber risk exposure. The proposed model can predict a negative time correlation, indicating that individual cyber exposure is increasing if no cyber loss has been reported in previous years, and vice versa. The results suggest that the probability of a cyber incident correlates with the subindustry, with the insurance sector being particularly exposed. The predicted financial losses from a cyber incident are less extreme than cited in recent investigations. The study confirms that cyber risks are heavy-tailed, jeopardising business operations and profitability
Simulation of satellites and constellations for the assessment of collision avoidance operations
No full textThe recent rapid increase in the satellite population in low Earth orbit (LEO) causes the number of conjunctions between operational spacecraft to increase sharply as well. In order to be able to cope with the associated workload in the future, it is necessary to define precise and acceptable rules that determine which spacecraft has to evade and how the avoidance manoeuvres shall be performed. To enable the assessment of different conceivable rule sets, a holistic simulation framework has been developed within the “Rules4CREAM” (R4C) activity at the Technical University of Darmstadt. Based on current and expected trends in growth and distribution of satellites in LEO, long-term propagation in the order of years can be performed for arbitrary satellite populations with the R4C framework which enables the generation of realistic conjunction data. This paper presents the core modules of this simulation framework. The satellites are described by osculating Keplerian orbits and analytical models are implemented to represent the most dominant perturbations in LEO. Different modes of station keeping are depicted within the satellite operations module of the simulation. For constellations, a generic model has been developed that is able to model the simultaneous deployment of multiple constellation planes as well as other operational key aspects specific to constellations. The models are validated with other simulations and real-life data. Finally two methods for the all-on-all conjunction detection are examined and the number of detected conjunctions is compared
Liberale Demokratietheorie in der Krise
No full textSchaut man auf den politikwissenschaftlichen Büchermarkt der letzten Jahre, so fällt eine deutliche Zunahme von Titeln ins Auge, die eine „Regression“, eine „Krise“, einen „Zerfall“ oder auch Anzeichen eines „Sterbens“ der liberalen Demokratie zum Gegenstand haben. Es handelt sich um Abhandlungen, die vor dem Hintergrund der aktuellen Welle des Populismus verfasst worden sind. Die These dieses Besprechungsessays lautet, dass in diesen Büchern mehr eine Ratlosigkeit über die Zukunft der Demokratie beziehungsweise eine nostalgische Sehnsucht nach einer vermeintlich intakten liberalen Demokratie, als es die Populisten noch nicht gab, zum Ausdruck kommt, als dass es den Autorinnen und Autoren gelingt, überzeugende Auswege aus der gegenwärtigen „Krise“ aufzuzeigen. Kompensiert wird diese Leerstelle zumeist mit normativen Vergewisserungsfloskeln, etwa, dass gegen die Krise der Demokratie nur „mehr Demokratie“ helfe oder wir alle gemeinsam gegen die Feinde der Demokratie aufstehen müssten
Die dunkle Seite der Ansichtskarte : Eine kollaborative Suche nach kontragenerischen Textpraktiken
Get PDF»Den Schreibern geht es praktisch nie schlecht«, so überschreibt die Rhein-Neckar-Zeitung einen Bericht über das Forschungsprojekt, in dessen Rahmen dieser Beitrag steht (RNZ vom 01.10.19). 1 ›Schreiber‹ sind hier Menschen, die Ansichtskarten verfassen. Gemeint ist mit dieser Überschrift natürlich nicht die tatsächliche Verfassung der Kartenschreiberinnen und -schreiber, sondern vielmehr die vermeintliche Tatsache, dass man auf Ansichtskarten bevorzugt über Positives schreibt – man will ja die wenigen Zeilen, die einem auf einer Ansichtskarte zur Verfügung stehen, nicht dazu nutzen, um sich und anderen die Laune zu verderben, die typischerweise eine Urlaubslaune ist. Noch dazu würden sich schlechte Nachrichten mit den Palmenstränden, Sonnenuntergängen, wolkenlosen Himmeln, Bergpanoramen und städtischen Schokoladenseiten beißen, die in der Regel die Vorderseite von Postkarten schmücken