Lazy Merging: From a Potential of Universes to a Universe of Potentials

Current collaboration workflows force participants to resolve conflicts eagerly, despite having insufficient knowledge and not being aware of their collaborators’ intentions. This is a major reason for bad decisions because it can disregard opinions within the team and cover up disagreements. In our concept of lazy merging we propose to aggregate conflicts as variant potentials. Variant potentials preserve concurrent changes and present the different options to the participants. They can be further merged and edited without restrictions and behave robustly even in complex collaboration scenarios. We use lattice theory to prove important properties and show the correctness and robustness of the collaboration protocol. With lazy merging, conflicts can be resolved deliberately, when all opinions within the team were explored and discussed. This facilitates alignment among team members and prepares them to arrive at the best possible decision that considers the knowledge of the whole team

Reproducibility Issues for BERT-based Evaluation Metrics

Reproducibility is of utmost concern in machine learning and natural language processing (NLP). In the field of natural language generation (especially machine translation), the seminal paper of Post (2018) has pointed out problems of reproducibility of the dominant metric, BLEU, at the time of publication. Nowadays, BERT-based evaluation metrics considerably outperform BLEU. In this paper, we ask whether results and claims from four recent BERT-based metrics can be reproduced. We find that reproduction of claims and results often fails because of (i) heavy undocumented preprocessing involved in the metrics, (ii) missing code and (iii) reporting weaker results for the baseline metrics. (iv) In one case, the problem stems from correlating not to human scores but to a wrong column in the csv file, inflating scores by 5 points. Motivated by the impact of preprocessing, we then conduct a second study where we examine its effects more closely (for one of the metrics). We find that preprocessing can have large effects, especially for highly inflectional languages. In this case, the effect of preprocessing may be larger than the effect of the aggregation mechanism (e.g., greedy alignment vs. Word Mover Distance).Comment: EMNLP 2022 Camera-Ready (captions fixed

Thermodynamics and reaction mechanism of urea decomposition

Selective catalytic reduction (SCR) for automotive applications depends on ammonia production from a urea-water solution by thermolysis and hydrolysis. In this process, undesired liquid and solid by-products are formed in the exhaust pipe. The formation and decomposition of these by-products have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Based on a previously published reaction mechanism by Brack et al. [1], a new reaction scheme is proposed that emphasizes the role of thermodynamic equilibrium of the reactants in liquid and solid phases [2]. The observed phenomenon of liquefaction and re-solidification of biuret in the temperature range 193–230 °C can be explained by formation of a eutectic mixture with urea. According to DSC data, the direct decomposition of urea to ammonia and isocyanic acid can be ruled out. The dominant route is a self-polymerisation of urea to biuret and triuret. Biuret and triuret decomposition are dominated by thermodynamic equilibria with gaseous isocyanic acid. For this, thermodynamic data of triuret have been refined. The apparent melting point of biuret at 193 °C is explained by the formation of a eutectic mixture within the urea-biuret-triuret-cyanuric acid ensemble. Furthermore, DSC data shows that cyanuric acid sublimates without decomposition at temperatures above 300 °C. Numerical simulations of the TGA and DSC experiments are performed by a multi-phase tank reactor model (DETCHEMMPTR [3]). The new reaction mechanism describes well the main features (decomposition steps and calorimetry) and dependencies (on heating rate and surface area) of the decompositions of urea, biuret, triuret and cyanuric acid. [1] W. Brack, B. Heine, F. Birkhold, M. Kruse, G. Schoch, S. Tischer and O. Deutschmann, “Kinetic modeling of urea decomposition based on systematic thermogravimetric analyses of urea and its most important by-products”, CES 106, 1–8 (2014). [2] S. Tischer, M. Börnhorst, J. Amsler, G. Schoch and O. Deutschmann, “Thermodynamics and reaction mechanism of urea decomposition”, PCCP, in press, DOI: 10.1039/C9CP01529A (2019). [3] www.detchem.co

Proof of Concept: Measuring Aortic Annulus Resistance by Means of Pressure-Volume Curves During Balloon Inflation to Guide Transcatheter Aortic Valve Implantation

This study assessed the basic working principle to measure aortic annulus resistance during balloon inflation for transcatheter aortic valve implantation (TAVI), by acquisition of pressure-volume curve for a guided semi-automatic implantation. A modular bench-system was used which allows the incremental inflation of valvuloplasty balloons by means of a stepper-motor driven linear axis with simultaneous recording of the pressure changes inside the system. Different porcine aortic xenografts were assessed by use of a non-compliant valvuloplasty balloon. In a second step transcatheter aortic stents were implanted inside target sized xenografts. The recorded pressure volume-curves showed that the system can accurately differentiate between different xenografts and assess the quality of the tissue rendering real-time analysis of pressure-volume curves during balloon-inflation possible, which has the potential to optimize the implantation procedure by direct adaptation to the patient specific anatomy and characteristics. Further investigations and development are warranted

Konzentrationsverschiebungen in einem kryogenen Gemischkältekreislauf mit mikrostrukturiertem Wärmeübertrager

Auf dem Joule-Thomson-Effekt basierende kryogene Gemischkältekreisläufe (cryogenic mixed-refrigerant cycles, CMRC) stellen eine kostengünstige, effiziente und beliebig skalierbare Technologie für die Kühlung bei Temperaturen unter 100 K dar. Damit eigenen sich Prozesse wie der mit weitsiedenden Kältemittelgemischen betriebene Linde-Hampson-Prozess beispielsweise für die Kühlung hochtemperatur-supraleitender Stromkabel. Im Betrieb führen die unterschiedlichen Löslichkeiten der Gemischkomponenten im Verdichteröl sowie Flüssigkeitsansammlungen in kalten Totvolumina zu einer Veränderung der zirkulierenden Gemischzusammensetzung, was in der Prozessentwicklung beachtet werden muss. Zur Optimierung der Prozesseffizienz und der Charakterisierung dieser Zusammensetzungsverschiebung beim Einsatz eines neuartigen kompakten mikrostrukturierten Wärmeübertragers wurden Untersuchungen an Stickstoff-Kohlenwasserstoff-Gemischen durchgeführt. Die Zusammensetzungen der eingesetzten Gemische wurden dabei gravimetrisch bei der Befüllung und im Betrieb off-line mit einem kalibrierten Gaschromatographen bestimmt. Die auf diese Weise erhobenen Daten zeigen eine geringere relative Verschiebung der Zusammensetzung als allgemein in der Literatur beschrieben, was auf das geringere innere Volumen des eingesetzten Wärmeübertragers zurückgeführt werden kann