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We consider the optimization problem of a large insurance company that wants to maximize the expected utility of its surplus through the optimal control of the proportional reinsurance. In addition, the insurer is exposed to the risk of default of its reinsurer at the worst possible time, a setting that is closely related to a scenario of the Swiss Solvency Test.
There had been interesting interactions between philosophical reflections, technical developments and the work of artists, poets and designers, starting especially in the 1950s and 1960s with a stimulating cell in Stuttgart and Ulm in Germany spreading mutual international interactions. The paper aims to describe the philosophical background of Max Bense with his research on the intellectual history of mathematics and the upcoming studies on technology and cybernetics. Together with communication theories and semiotics, new aesthetics such as cybernetic aesthetics had been worked out, based on the notions of information and sign. This background stimulated international students, artists and researchers from different creative disciplines for methodical approaches leading to first computer art experiments. The interrelations in these fields with Latin America are in the focus of these studies. Students, artists, and poets from Latin America, especially Brazil, came to Germany for studies and exhibitions in the creative scientific cell around Max Bense. Some of them stayed in Europe, but the exchange developed also in the opposite direction, traveling to and working in Latin America. Some of those fruitful international interrelations will be described and reflected.
In the strive for the climate-neutral and ultra-low emission vehicle powertrains of the future, synthetic fuels produced from renewable sources will play a major role. Polyoxymethylene dimethyl ethers (POMDME or “OME”) produced from renewable hydrogen are a very promising candidate for zero-impact emissions in future CI engines. To optimize the utilisation of these fuels in terms of efficiency, performance and emissions, it is not only necessary to adapt the combustion parameters, but especially to optimize the injection and mixture formation process. In the present work, the spray break-up behavior and mixture formation of OME fuel is investigated numerically in 3D CFD and validated against experimental data from optical measurements in a high pressure/high temperature chamber using Schlieren and Mie scattering. For comparison, the same operating points using conventional diesel fuel were measured in the optical chamber, and the CFD modeling was optimized based on these data. To model the spray-breakup phenomena reliably, the primary break-up model according to Fischer is used, taking into account the nozzle internal flow in a detailed calculation of the disperse droplet phase. As OME has not yet been investigated very intensively with respect to its chemico-physical properties, chemical analyses of the substance properties were carried out to capture the most important parameters correctly in the simulation. With this approach, the results of the optical spray measurement could be reproduced well by the numerical model for the cases studied here, laying the basis for further numerical studies of OME sprays, including real engine operation.
Synthetic Biology is revolutionizing biological research by introducing principles of mechanical engineering, including the standardization of genetic parts and standardized part assembly routes. Both are realized in the Modular Cloning (MoClo) strategy. MoClo allows for the rapid and robust assembly of individual genes and multigene clusters, enabling iterative cycles of gene design, construction, testing, and learning in short time. This is particularly true if generation times of target organisms are short, as is the case for the unicellular green alga Chlamydomonas reinhardtii. Testing a gene of interest in Chlamydomonas with MoClo requires two assembly steps, one for the gene of interest itself and another to combine it with a selection marker. To reduce this to a single assembly step, we constructed five new destination vectors. They contain genes conferring resistance to commonly used antibiotics in Chlamydomonas and a site for the direct assembly of basic genetic parts. The vectors employ red/white color selection and, therefore, do not require costly compounds like X-gal and IPTG. mCherry expression is used to demonstrate the functionality of these vectors.
Many real-world optimization and decision-making problems comprise several, partly conflicting objective functions. The English saying “Quality has its price” is just as true on a large scale as it is in private sphere and, therefore, quality and price are a typical pair of conflicting objective functions that are very common in applications. Yet, in industrial applications, both quality and cost may be understood in the specific context and differ whether a transportation, a production, or a planning problem is considered. Other objective functions that are receiving increasing attention in real-world decision-making situations are, for example, robustness, time, sustainability, adaptability, or longevity.
The electrochemical process of microbial electrosynthesis (MES) is used to drive the metabolism of electroactive microorganisms for the production of valuable chemicals and fuels. MES combines the advantages of electrochemistry, engineering, and microbiology and offers alternative production processes based on renewable raw materials and regenerative energies. In addition to the reactor concept and electrode design, the biocatalysts used have a significant influence on the performance of MES. Thus, pure and mixed cultures can be used as biocatalysts. By using mixed cultures, interactions between organisms, such as the direct interspecies electron transfer (DIET) or syntrophic interactions, influence the performance in terms of productivity and the product range of MES. This review focuses on the comparison of pure and mixed cultures in microbial electrosynthesis. The performance indicators, such as productivities and coulombic efficiencies (CEs), for both procedural methods are discussed. Typical products in MES are methane and acetate, therefore these processes are the focus of this review. In general, most studies used mixed cultures as biocatalyst, as more advanced performance of mixed cultures has been seen for both products. When comparing pure and mixed cultures in equivalent experimental setups a 3-fold higher methane and a nearly 2-fold higher acetate production rate can be achieved in mixed cultures. However, studies of pure culture MES for methane production have shown some improvement through reactor optimization and operational mode reaching similar performance indicators as mixed culture MES. Overall, the review gives an overview of the advantages and disadvantages of using pure or mixed cultures in MES.
In this paper, we devise a stochastic asset–liability management (ALM) model for a life insurance company and analyze its influence on the balance sheet within a low-interest rate environment. In particular, a flexible procedure for the generation of insurers’ compressed contract portfolios that respects the given biometric structure is presented, extending the existing literature on stochastic ALM modeling. The introduced balance sheet model is in line with the principles of double-entry bookkeeping as required in accounting. We further focus on the incorporation of new business, i.e. the addition of newly concluded contracts and thus of insured in each period. Efficient simulations are obtained by integrating new policies into existing cohorts according to contract-related criteria. We provide new results on the consistency of the balance sheet equations. In extensive simulation studies for different scenarios regarding the business form of today’s life insurers, we utilize these to analyze the long-term behavior and the stability of the components of the balance sheet for different asset–liability approaches. Finally, we investigate the robustness of two prominent investment strategies against crashes in the capital markets, which lead to extreme liquidity shocks and thus threaten the insurer’s financial health.
Lattice Boltzmann method for antiplane shear deformation: non-lattice-conforming boundary conditions
(2022)
In this work, two different approaches to treat boundary conditions in a lattice Boltzmann method (LBM) for the wave equation are presented. We interpret the wave equation as the governing equation of the displacement field of a solid under simplified deformation assumptions, but the algorithms are not limited to this interpretation. A feature of both algorithms is that the boundary does not need to conform with the discretization, i.e., the regular lattice. This allows for a larger flexibility regarding the geometries that can be handled by the LBM. The first algorithm aims at determining the missing distribution functions at boundary lattice points in such a way that a desired macroscopic boundary condition is fulfilled. The second algorithm is only available for Neumann-type boundary conditions and considers a balance of momentum for control volumes on the mesoscopic scale, i.e., at the scale of the lattice spacing. Numerical examples demonstrate that the new algorithms indeed improve the accuracy of the LBM compared to previous results and that they are able to model boundary conditions for complex geometries that do not conform with the lattice.