@article{ThemaWeidlichHoerletal., author = {Thema, Martin and Weidlich, Tobias and H{\"o}rl, Manuel and Bellack, Annett and M{\"o}rs, Friedemann and Hackl, Florian and Kohlmayer, Matthias and Gleich, Jasmin and Stabenau, Carsten and Trabold, Thomas and Neubert, Michael and Ortloff, Felix and Brotsack, Raimund and Schmack, Doris and Huber, Harald and Hafenbradl, Doris and Karl, J{\"u}rgen and Sterner, Michael}, title = {Biological CO2-Methanation: An Approach to Standardization}, series = {Energies}, volume = {12}, journal = {Energies}, number = {9}, publisher = {MDPI}, doi = {10.3390/en12091670}, pages = {1 -- 32}, abstract = {Power-to-Methane as one part of Power-to-Gas has been recognized globally as one of the key elements for the transition towards a sustainable energy system. While plants that produce methane catalytically have been in operation for a long time, biological methanation has just reached industrial pilot scale and near-term commercial application. The growing importance of the biological method is reflected by an increasing number of scientific articles describing novel approaches to improve this technology. However, these studies are difficult to compare because they lack a coherent nomenclature. In this article, we present a comprehensive set of parameters allowing the characterization and comparison of various biological methanation processes. To identify relevant parameters needed for a proper description of this technology, we summarized existing literature and defined system boundaries for Power-to-Methane process steps. On this basis, we derive system parameters providing information on the methanation system, its performance, the biology and cost aspects. As a result, three different standards are provided as a blueprint matrix for use in academia and industry applicable to both, biological and catalytic methanation. Hence, this review attempts to set the standards for a comprehensive description of biological and chemical methanation processes.}, language = {en} } @article{BauerLauf, author = {Bauer, Ulrich and Lauf, Wolfgang}, title = {Conformal Mapping onto a Doubly Connected Circular Arc Polygonal Domain}, series = {Computational Methods and Function Theory}, volume = {19}, journal = {Computational Methods and Function Theory}, publisher = {Springer Nature}, doi = {10.1007/s40315-018-0256-0}, pages = {77 -- 96}, abstract = {This paper presents a construction principle for the Schwarzian derivative of conformal mappings from an annulus onto doubly connected domains bounded by polygons of circular arcs.}, language = {en} } @article{RoeslSeitzToedter, author = {R{\"o}sl, Gerhard and Seitz, Franz and T{\"o}dter, Karl-Heinz}, title = {The Cost of Overcoming the Zero Lower-Bound: A Welfare Analysis}, series = {Economies}, volume = {7}, journal = {Economies}, number = {3}, publisher = {MDPI}, doi = {10.3390/economies7030067}, pages = {1 -- 18}, abstract = {To broaden the operational scope of monetary policy, several authors suggest cash abolition as an appropriate means of breaking through the zero lower-bound. We argue that the welfare costs of bypassing the zero lower-bound by getting rid of cash entirely are analytically equivalent to negative interest rates on cash holdings. Using a money-in-the-utility-function model, we measure in two ways the welfare loss consumers as money holders would be forced to bear once the zero lower-bound is broken: in terms of the amount needed to compensate consumers (compensated variation), and as excess burden (deadweight loss) imposed on the economy as a whole. We calibrated the model for the euro area and for Germany. Our findings suggest that the welfare losses of negative interest rates incurred by consumers as holders of cash and transaction balances (M3) are large and enduring, notably if implemented in the current low-interest rate environment.}, language = {en} } @article{ChenSongZhangetal., author = {Chen, Rui and Song, Ruizhou and Zhang, Zhuo and Bai, Long and Liu, Fuqiang and Jiang, Pei and Sindersberger, Dirk and Monkman, Gareth J. and Guo, Jianglong}, title = {Bio-Inspired Shape-Adaptive Soft Robotic Grippers Augmented with Electroadhesion Functionality}, series = {Soft Robotics}, volume = {6}, journal = {Soft Robotics}, number = {6}, publisher = {Mary Ann Liebert}, doi = {10.1089/soro.2018.0120}, pages = {701 -- 712}, abstract = {Soft robotic grippers (SRGs) have been extensively employed in robotic grasping and manipulation applications due to the fact that they are beneficial for pick-and-place of difficult-to-handle and delicate objects with various geometries and stiffness in a comfortable and safer way. This article presents a bio-inspired and shape-adaptive SRG augmented with electroadhesion (EA) functionality, FinEA, by a cost-effective combination of a Fin Ray structured two-fingered SRG with two soft-stretchable EA pads. The EA pads were manufactured by screen printing a layer of electrically conductive and elastomeric carbon black powder mixed with polydimethylsiloxane onto a dielectric substrate. The compliant Fin Ray fingers, composed of soft longitudinal beams and rigid cross beams, were structurally optimized by the finite element method using ABAQUS/CAE based on three key parameters: the open angle of the longitudinal beams, the spacing between the cross beams, and the incline angle of the cross beams. The soft beams were produced by a traditional soft lithography method, whereas the rigid cross beams were three-dimensionally printed. The resultant FinEA grippers were capable of lifting not only flat/thin materials without distorting them due to the employment of EA, but also concave and convex objects due to the passively shape-adaptive Fin Ray structure and the EA functionality. In addition, the proposed FinEA grippers were able to grasp delicate materials and objects whose diameters are larger than the overall gripper length. Furthermore, 65\% more weight in shear were picked up by the FinEA gripper when 4 kV was applied compared with 0 V. The FinEA concept provides useful and alternative solution for controllable adhesion-based SRGs and may facilitate the inspiration and development of future SRGs with added functionality and enhanced versatility.}, language = {en} } @article{GalanBriendlThumannetal., author = {Galan, Isabel and Briendl, Lukas G. and Thumann, Maria and Steindl, Florian and Roeck, Rudolf and Kusterle, Wolfgang and Mittermayr, Florian}, title = {Filler Effect in Shotcrete}, series = {Materials}, volume = {12}, journal = {Materials}, number = {19}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ma12193221}, pages = {1 -- 24}, abstract = {The effects of fine limestone powder on the early hydration of cementitious systems accelerated by means of alkali-free aluminum sulfate based products, commonly used for shotcrete applications, were investigated in the course of laboratory and real scale tests. In binary (CEM I + limestone) and ternary (CEM I + limestone + slag) systems the addition of fine limestone led to an enhancement of the hydration degree and strength development at early times (<24 h). The formation of ettringite, aluminate hydrates, and C-S-H is affected by the joint action of the setting accelerator and the fine limestone. Accelerator and limestone, in combination with the cement, can be optimized to enhance ettringite and silicate reaction, in some cases coupled with aluminate reaction inhibition, to produce mixes suitable for sprayed concrete applications. Such optimization can help to reduce the cement content in the mixes without compromising the early strength development of the shotcrete.}, language = {en} } @article{ChatzitakisSafarovOpferkuchetal., author = {Chatzitakis, Paris and Safarov, Javid and Opferkuch, Frank and Dawoud, Belal}, title = {Experimental investigation of an absorption heat pump with organic working pairs}, series = {Applied Thermal Engineering}, volume = {163}, journal = {Applied Thermal Engineering}, number = {December}, publisher = {Elsevier}, doi = {10.1016/j.applthermaleng.2019.114311}, abstract = {As part of a systematic approach towards the search for alternative absorption heat pump (AHP) working pairs that could potentially provide comparable performance to conventional ones, a previous work performed a detailed theoretical cycle analysis and simulation that revealed concrete correlations between key working fluid thermophysical properties and AHP performance indicators. Following this work, targeted combinations of two organic refrigerants, 2,2,2-trifluoroethanol (TFE) and 2,2,3,3,3-pentafluoropropanol (5FP) and two organic absorbents, 1,3-dimethyl-2-imidazolidinone (DMI) and 2-pyrrolidone (PYR) were tested in a prototype 5 kW AHP, based on a highly compact plate heat exchanger design, which has been previously introduced. The purpose of this effort was to test the findings of the previous work with experimental measurements. The working pair combinations were also subjected to vapor liquid equilibrium (VLE) and viscosity measurements, in order to determine reliable activity coefficient and improve the accuracy of the simulations. The experimental performance data agree well with the COP simulations and show to be consistent with the conclusions derived from the previous theoretical work.}, language = {en} } @article{BraunDurnerRabletal., author = {Braun, Peter and Durner, Bernhard and Rabl, Hans-Peter and Matysik, Frank-Michael}, title = {Investigations on the decomposition of AdBlue urea in the liquid phase at low temperatures by an electrochemically induced pH shift}, series = {Monatshefte f{\"u}r Chemie}, volume = {150}, journal = {Monatshefte f{\"u}r Chemie}, number = {9}, publisher = {Springer}, doi = {10.1007/s00706-019-02406-6}, pages = {1633 -- 1641}, abstract = {Ammonia-based selective catalytic reduction (SCR) systems are the most widely used technology for reduction of nitrogen oxide emissions from lean-burn engines such as diesel engines. However, at low exhaust temperatures, the SCR process is limited by difficulties in the decomposition of the ammonia precursor urea, which is carried on-board using an aqueous solution "AdBlue". In this study, the decomposition of AdBlue urea induced by electrical current and the resulting associated pH shifts were investigated in a divided cell configuration in the liquid phase. The decomposition was found to be favored in both electrochemical compartments, anodic and cathodic, at temperatures of 60-80 degrees C compared to a reference without electrochemical treatment. In addition to the determination of ammonia contents using an ammonia sensor, IC/HPLC analyses were carried out for each sample. Different side products such as biuret, nitrate, cyanuric acid, ammelide, and others were formed. In the anodic compartment, nitrate formation could be observed due to oxidation of ammonia at the electrode surface. [GRAPHICS] .}, language = {en} } @article{BraunRablMatysik, author = {Braun, Peter and Rabl, Hans-Peter and Matysik, Frank-Michael}, title = {Investigations on the Liquid-Phase Decomposition of AdBlue Urea for the Selective Catalytic Reduction Process}, series = {Chemie Ingenieur Technik}, volume = {91}, journal = {Chemie Ingenieur Technik}, number = {7}, publisher = {Wiley}, doi = {10.1002/cite.201800055}, pages = {961 -- 968}, abstract = {Difficulties in decomposing AdBlue to ammonia limit the applicability of selective catalytic reduction systems at low exhaust temperatures. Investigations on the decomposition of AdBlue in the liquid phase under elevated pressure at temperatures up to 165 degrees C were carried out. Besides effects of inorganic catalysts, the impact of pH on urea decomposition was examined. After dissolution in aqueous phase, the compounds ZnO, WO3, and MoO3 were found to be effective in liquid-phase AdBlue decomposition. However, the efficiency was dropping significantly over few hours. Decomposition of AdBlue urea was also found to be favored for alkaline and acidic conditions.}, language = {en} } @article{BodnarukKalitaKulyketal., author = {Bodnaruk, Andrii V. and Kalita, Viktor M. and Kulyk, Mykola M. and Lozenko, Albert F. and Ryabchenko, Sergey M. and Snarskii, Andrei A. and Brunhuber, Alexander and Shamonin (Chamonine), Mikhail}, title = {Temperature blocking and magnetization of magnetoactive elastomers}, series = {Journal of Magnetism and Magnetic Materials}, volume = {471}, journal = {Journal of Magnetism and Magnetic Materials}, number = {February}, publisher = {Elsevier}, doi = {10.1016/j.jmmm.2018.10.005}, pages = {464 -- 467}, abstract = {The magnetization of a magnetoactive elastomer (MAE) with microparticles of soft magnetic carbonyl iron embedded in a highly elastic matrix has been studied. It is shown that at high temperatures its magnetization curve has the form of a specific hysteresis loop. This hysteresis is attributed to the influence of displacement of magnetized particles in the elastically soft elastomer matrix under the effect of magnetic forces, leading to the change of magnetic interaction between the particles. In this case, there is a maximum in the field dependence of the magnetic susceptibility, the occurrence of which has been associated with the competition between rearrangement of particles, when they are displaced in a magnetic field, and saturation of particles' magnetization. When the MAE is cooled below approximately 225 K, both the magnetic hysteresis and the maximum in the field dependence of the magnetic susceptibility disappear. When the MAE material is cooled below the solidification temperature of the elastomer matrix, the displacements of the magnetic particles during magnetization are blocked by the rigid matrix. The magnetization reversal of the MAE is reversible. This means that the shape of subsequent magnetization loops remains constant and the sample returns into the initial non-magnetized state after the magnetic field is turned off.}, language = {en} } @article{BodnarukAndriiVBrunhuberetal., author = {Bodnaruk, and Andrii V., and Brunhuber, Alexander and Kalita, Viktor M. and Kulyk, Mykola M. and Kurzweil, Peter and Snarskii, Andrei A. and Lozenko, Albert F. and Ryabchenko, Sergey M. and Shamonin (Chamonine), Mikhail}, title = {Magnetic anisotropy in magnetoactive elastomers, enabled by matrix elasticity}, series = {Polymer}, volume = {162}, journal = {Polymer}, number = {January}, publisher = {Elsevier}, doi = {10.1016/j.polymer.2018.12.027}, pages = {63 -- 72}, abstract = {Polydimethylsiloxane based magnetoactive elastomers demonstrate above the melting transition range (e.g. at room temperature) an induced uniaxial magnetic anisotropy, which grows with increasing magnetic field. By freezing a material down to 150 K, displaced iron microparticles are immobilized, so that the magnetic anisotropy can be measured. Magnetic anisotropy "constant" is a consequence of particle displacements and a characteristic of the energy of internal deformations in the polymer matrix. The maximum anisotropy constant of the filling is at least one order of magnitude larger than the shear modulus of the pure elastomer (matrix). In a magnetic field, the gain in the rigidity of the composite material is attributed to the magnetomechanical coupling, which is in turn a source of anisotropy. The concept of effective magnetic field felt by the magnetization allows one to explain the magnetization curve at room temperature from low-temperature measurements. The results can be useful for developing vibration absorbers and isolators.}, language = {en} }