Expression Templates Revisited: A Performance Analysis of the Current ET Methodology

In the last decade, Expression Templates (ET) have gained a reputation as an efficient performance optimization tool for C++ codes. This reputation builds on several ET-based linear algebra frameworks focused on combining both elegant and high-performance C++ code. However, on closer examination the assumption that ETs are a performance optimization technique cannot be maintained. In this paper we demonstrate and explain the inability of current ET-based frameworks to deliver high performance for dense and sparse linear algebra operations, and introduce a new "smart" ET implementation that truly allows the combination of high performance code with the elegance and maintainability of a domain-specific language.Comment: 16 pages, 7 figure

Mean-Field Liquidation Games with Market Drop-out

We consider a novel class of portfolio liquidation games with market drop-out ("absorption"). More precisely, we consider mean-field and finite player liquidation games where a player drops out of the market when her position hits zero. In particular round-trips are not admissible. This can be viewed as a no statistical arbitrage condition. In a model with only sellers we prove that the absorption condition is equivalent to a short selling constraint. We prove that equilibria (both in the mean-field and the finite player game) are given as solutions to a non-linear higher-order integral equation with endogenous terminal condition. We prove the existence of a unique solution to the integral equation from which we obtain the existence of a unique equilibrium in the MFG and the existence of a unique equilibrium in the $N$-player game. We establish the convergence of the equilibria in the finite player games to the obtained mean-field equilibrium and illustrate the impact of the drop-out constraint on equilibrium trading rates

Fiabilité intra- et inter-examinateur du dynamomètre microFET2 pour mesurer la force isométrique maximale du membre inférieur: protocole pour une étude diagnostique de type transversal

Hypothèse : Notre hypothèse est qu’une standardisation de la procédure d’utilisation du dynamomètre microFET2 diminue l’erreur de mesure et influence favorablement la fiabilité de l’appareil. Objectif : Notre objectif est d’élaborer un protocole d’utilisation du dynamomètre microFET2 avec une procédure standardisée et détaillée pour évaluer la force isométrique maximale du membre inférieur. L’application de ce protocole permettra de répondre à l’objectif principal du projet qui est d’évaluer la fiabilité intra- et inter-examinateur du dynamomètre microFET2. [3] Issue : Lors de cette étude, nous mesurerons la force isométrique maximale à l’aide du microFET2 qui nous donnera les résultats en newtons. L’issue de ce projet sera la fiabilité intra- et inter-examinateur de ces mesures, évaluée à l’aide du coefficient de corrélation intra-classe (ICC)

IR Spectroscopy as a Method for Online Electrolyte State Assessment in RFBs

Abstract The transition from fossil to renewable energy sources requires adequate storage technologies due to the intermittency of the supplied energy. With respect to this, organic redox‐flow batteries (ORFBs) represent a promising concept for the storage of electricity on a large scale at economically justifiable costs. However, these storage technologies can only be operated reliably if parameters representing the actual condition of the storage medium (i.e., the electrolyte) can be accurately assessed. These so‐called electrolyte state variables are represented by two key figures of merit: state of charge (SOC), a measure of the amount of charge that the electrolyte currently holds; and state of health (SOH), representing the amount of charge that the electrolyte is able to store given its current condition. The herein presented IR‐based approach is able to simultaneously provide reliable, fast, accurate, and precise estimates for both SOC and SOH parameters at any point in time and independent of the current battery status. The method is able to provide a time resolution in the range of minutes, is independent of the electrolyte temperature and can be applied to nearly all organic‐based redox‐active materials and solvents, while potentially being applicable to inorganic RFBs, such as vanadium‐based systems, as well.Redox‐flow batteries (RFBs) provide a unique and scalable storage solution for green energy. However, they can only be operated safely when parameters representing the battery state are precisely known at any point in time. The presented IR‐spectroscopic method is able to generate accurate and precise estimates for the crucial State‐of‐Charge and State‐of‐Health variables of RFB electrolytes. imag

Selective metal‐complexation on polymeric templates and their investigation via isothermal titration calorimetry

Selective complexation of metal ions represents a powerful tool for the development of versatile supramolecular architectures. While research in the field of molecular devices and machinery is sophisticated, the selective formation of metal complexes is not prevalent in polymer chemistry. Thus, the implementation of orthogonal binding concepts into a polymeric matrix is presented. In this context, an end‐functionalized poly( N ‐isopropylacrylamide) (PNIPAm) carrying zinc‐porphyrin (ZnTPP) as well as a terpyridine (tpy) ligand side by side is utilized. With these binding sites, the polymer can simultaneously interact with a pyridine moiety via a ZnTPP interaction and a terpyridine unit by the formation of a bis‐terpyridine complex. The complexation behavior of this polymer and different model compounds is intensively investigated by isothermal titration calorimetry. The obtained results indicate that the reported orthogonality of these two systems is successfully transferred into a functional polymeric architecture

Comparing Microwave and Classical Synthesis of Oxymethylene Dimethyl Ethers

Polyoxymethylene dimethyl ethers (OME n ) are considered as substituents or additives for fossil diesel fuel. Efficiency of the synthesis is crucial for the development of industrial scale production plants. Therefore, the design of suitable catalysts and the efficient heating play important roles in OME fuel synthesis. In this work, microwave‐assisted synthesis (MAS) is carried out and compared to a classical approach using standard thermal heating. Different polymeric materials, e.g., Amerlyst15, are utilized as catalysts, and screened for the catalytic synthesis of OME. Within this approach, the kinetics of the reaction are analyzed in detail

Hydrophilic Crosslinked TEMPO‐Methacrylate Copolymers – a Straight Forward Approach towards Aqueous Semi‐Organic Batteries

Abstract Crosslinked hydrophilic poly(2,2,6,6‐tetramethylpiperidinyl‐ N ‐oxyl‐co‐[2‐(methacryloyloxy)‐ethyl]trimethyl ammonium chloride) [poly(TEMPO‐ co ‐METAC)] polymers with different monomer ratios are synthesized and characterized regarding a utilization as electrode material in organic batteries. These polymers can be synthesized rapidly utilizing commercial starting materials and reveal an increased hydrophilicity compared to the state‐of‐the‐art poly(2,2,6,6‐tetramethylpiperidinyl‐ N ‐oxyl‐4‐methacrylate) (PTMA). By increasing the hydrophilicity of the polymer, a preparation of cathode composites is enabled, which can be used for aqueous semi‐organic batteries. Detailed battery testing confirms that the additional METAC groups do not impair the battery behavior while enabling straight‐forward zinc‐TEMPO batteries.Organic cathode in aqueous electrolyte : A crosslinked hydrophilic 2,2,6,6‐tetramethylpiperidine‐ N ‐oxyl radical (TEMPO) bearing polymer was synthesized, which enables aqueous battery chemistries that have not been compatible with poly(TEMPO‐methacrylate) derived structures before. Extensive battery testing was performed, to reveal the battery chemistry of the polymer containing composite electrodes in an aqueous semi‐organic zinc coin‐cell setup. imag

Quantification of triple‐shape memory behavior of polymers utilizing tension and torsion

Abstract Shape‐memory polymers (SMPs) are well investigated smart materials. With their ability to memorize their original shape they are interesting candidates for a large range of applications. Certain SMPs feature triple shape‐memory behavior. In these cases, it is possible to fix two different temporary shapes. However, the exact quantification of the individual steps regarding their programming and recovery rate is difficult and has not been possible so far. In this work, a novel approach for the analysis and exact quantification of triple SMPs is presented. By applying a customized rheology protocol, it is possible to perform and to analyze torsional and tensional experiments simultaneously. Consequently, different shapes in different directions (vertical and horizontal) can be fixed and the individual steps can be investigated independently at different switching temperatures

State of charge and state of health assessment of viologens in aqueous-organic redox-flow electrolytes using in situ IR spectroscopy and multivariate curve resolution

Aqueous-organic redox flow batteries (RFBs) have gained considerable interest in recent years, given their potential for an economically viable energy storage at large scale. This, however, strongly depends on both the robustness of the underlying electrolyte chemistry against molecular decomposition reactions as well as the device's operation. With regard to this, the presented study focuses on the use of in situ IR spectroscopy in combination with a multivariate curve resolution approach to gain insight into both the molecular structures of the active materials present within the electrolyte as well as crucial electrolyte state parameters, represented by the electrolyte's state of charge (SOC) and state of health (SOH). To demonstrate the general applicability of the approach, methyl viologen (MV) and bis(3-trimethylammonium)propyl viologen (BTMAPV) are chosen, as viologens are frequently used as negolytes in aqueous-organic RFBs. The study's findings highlight the impact of in situ spectroscopy and spectral deconvolution tools on the precision of the obtainable SOC and SOH values. Furthermore, the study indicates the occurrence of multiple viologen dimers, which possibly influence the electrolyte lifetime and charging characteristics