@inproceedings{MilijašŠakićMarinkovićetal.2021, author = {Milijaš, Aleksa and Šakić, Bogdan and Marinković, Marko and Butenweg, Christoph}, title = {Experimental investigation of behaviour of masonry infilled RC frames under out-of-plane loading}, series = {Proceedings of COMPDYN 2021}, booktitle = {Proceedings of COMPDYN 2021}, editor = {Papadrakakis, Manolis and Fragiadakis, Michalis}, publisher = {National Technical University of Athens}, address = {Athen}, isbn = {978-618-85072-5-8}, issn = {2623-3347}, doi = {10.7712/120121.8528.18914}, pages = {829 -- 846}, year = {2021}, abstract = {Masonry infills are commonly used as exterior or interior walls in reinforced concrete (RC) frame structures and they can be encountered all over the world, including earthquake prone regions. Since the middle of the 20th century the behaviour of these non-structural elements under seismic loading has been studied in numerous experimental campaigns. However, most of the studies were carried out by means of in-plane tests, while there is a lack of out-of-plane experimental investigations. In this paper, the out-of-plane tests carried out on full scale masonry infilled frames are described. The results of the out-of-plane tests are presented in terms of force-displacement curves and measured out-of-plane displacements. Finally, the reliability of existing analytical approaches developed to estimate the out-of-plane strength of masonry infills is examined on presented experimental results.}, language = {en} } @article{KezerashviliDachwald2021, author = {Kezerashvili, Roman Ya and Dachwald, Bernd}, title = {Preface: Solar sailing: Concepts, technology, and missions II}, series = {Advances in Space Research}, volume = {67}, journal = {Advances in Space Research}, number = {9}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0273-1177}, doi = {10.1016/j.asr.2021.01.037}, pages = {2559 -- 2560}, year = {2021}, language = {en} } @article{HagenkampBlankeDoering2021, author = {Hagenkamp, Markus and Blanke, Tobias and D{\"o}ring, Bernd}, title = {Thermoelectric building temperature control: a potential assessment}, series = {International Journal of Energy and Environmental Engineering}, volume = {13}, journal = {International Journal of Energy and Environmental Engineering}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/s40095-021-00424-x}, pages = {241 -- 254}, year = {2021}, abstract = {This study focuses on thermoelectric elements (TEE) as an alternative for room temperature control. TEE are semi-conductor devices that can provide heating and cooling via a heat pump effect without direct noise emissions and no refrigerant use. An efficiency evaluation of the optimal operating mode is carried out for different numbers of TEE, ambient temperatures, and heating loads. The influence of an additional heat recovery unit on system efficiency and an unevenly distributed heating demand are examined. The results show that TEE can provide heat at a coefficient of performance (COP) greater than one especially for small heating demands and high ambient temperatures. The efficiency increases with the number of elements in the system and is subject to economies of scale. The best COP exceeds six at optimal operating conditions. An additional heat recovery unit proves beneficial for low ambient temperatures and systems with few TEE. It makes COPs above one possible at ambient temperatures below 0 ∘C. The effect increases efficiency by maximal 0.81 (from 1.90 to 2.71) at ambient temperature 5 K below room temperature and heating demand Q˙h=100W but is subject to diseconomies of scale. Thermoelectric technology is a valuable option for electricity-based heat supply and can provide cooling and ventilation functions. A careful system design as well as an additional heat recovery unit significantly benefits the performance. This makes TEE superior to direct current heating systems and competitive to heat pumps for small scale applications with focus on avoiding noise and harmful refrigerants.}, language = {en} } @article{SpietzSproewitzSeefeldtetal.2021, author = {Spietz, Peter and Spr{\"o}witz, Tom and Seefeldt, Patric and Grundmann, Jan Thimo and Jahnke, Rico and Mikschl, Tobias and Mikulz, Eugen and Montenegro, Sergio and Reershemius, Siebo and Renger, Thomas and Ruffer, Michael and Sasaki, Kaname and Sznajder, Maciej and T{\´o}th, Norbert and Ceriotti, Matteo and Dachwald, Bernd and Macdonald, Malcolm and McInnes, Colin and Seboldt, Wolfgang and Quantius, Dominik and Bauer, Waldemar and Wiedemann, Carsten and Grimm, Christian D. and Hercik, David and Ho, Tra-Mi and Lange, Caroline and Schmitz, Nicole}, title = {Paths not taken - The Gossamer roadmap's other options}, series = {Advances in Space Research}, volume = {67}, journal = {Advances in Space Research}, number = {9}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0273-1177}, doi = {10.1016/j.asr.2021.01.044}, pages = {2912 -- 2956}, year = {2021}, language = {en} } @article{AkimbekovDigelAbdievaetal.2021, author = {Akimbekov, Nuraly S. and Digel, Ilya and Abdieva, Gulzhamal and Ualieva, Perizat and Tastambek, Kuanysh}, title = {Lignite biosolubilization and bioconversion by Bacillus sp.: the collation of analytical data}, series = {Biofuels}, volume = {12}, journal = {Biofuels}, number = {3}, publisher = {Taylor \& Francis}, address = {London}, issn = {1759-7277}, pages = {247 -- 258}, year = {2021}, abstract = {The vast metabolic potential of microbes in brown coal (lignite) processing and utilization can greatly contribute to innovative approaches to sustainable production of high-value products from coal. In this study, the multi-faceted and complex coal biosolubilization process by Bacillus sp. RKB 7 isolate from the Kazakhstan coal-mining soil is reported, and the derived products are characterized. Lignite solubilization tests performed for surface and suspension cultures testify to the formation of numerous soluble lignite-derived substances. Almost 24\% of crude lignite (5\% w/v) was solubilized within 14 days under slightly alkaline conditions (pH 8.2). FTIR analysis revealed various functional groups in the obtained biosolubilization products. Analyses of the lignite-derived humic products by UV-Vis and fluorescence spectrometry as well as elemental analysis yielded compatible results indicating the emerging products had a lower molecular weight and degree of aromaticity. Furthermore, XRD and SEM analyses were used to evaluate the biosolubilization processes from mineralogical and microscopic points of view. The findings not only contribute to a deeper understanding of microbe-mineral interactions in coal environments, but also contribute to knowledge of coal biosolubilization and bioconversion with regard to sustainable production of humic substances. The detailed and comprehensive analyses demonstrate the huge biotechnological potential of Bacillus sp. for agricultural productivity and environmental health.}, language = {en} } @article{HeiligersSchoutetensDachwald2021, author = {Heiligers, Jeannette and Schoutetens, Frederic and Dachwald, Bernd}, title = {Photon-sail equilibria in the alpha centauri system}, series = {Journal of Guidance, Control, and Dynamics}, volume = {44}, journal = {Journal of Guidance, Control, and Dynamics}, number = {5}, issn = {1533-3884}, doi = {10.2514/1.G005446}, pages = {1053 -- 1061}, year = {2021}, language = {en} } @article{Bung2021, author = {Bung, Daniel Bernhard}, title = {Extreme flooding in Western Germany: some thoughts on hazards, return periods and risk}, series = {Hydrolink}, journal = {Hydrolink}, number = {4}, publisher = {International Association for Hydro-Environment Engineering and Research (IAHR)}, address = {Madrid}, pages = {108 -- 113}, year = {2021}, abstract = {The low-pressure system Bernd involved extreme rainfalls in the Western part of Germany in July 2021, resulting in major floods, severe damages and a tremendous number of casualties. Such extreme events are rare and full flood protection can never be ensured with reasonable financial means. But still, this event must be starting point to reconsider current design concepts. This article aims at sharing some thoughts on potential hazards, the selection of return periods and remaining risk with the focus on Germany.}, language = {en} } @inproceedings{GrundmannBorellaCeriottietal.2021, author = {Grundmann, Jan Thimo and Borella, Laura and Ceriotti, Matteo and Chand, Suditi and Cordero, Federico and Dachwald, Bernd and Fexer, Sebastian and Grimm, Christian D. and Hendrikse, Jeffrey and Herč{\´i}k, David and Herique, Alain and Hillebrandt, Martin and Ho, Tra-Mi and Kesseler, Lars and Laabs, Martin and Lange, Caroline and Lange, Michael and Lichtenheldt, Roy and McInnes, Colin R. and Moore, Iain and Peloni, Alessandro and Plettenmeier, Dirk and Quantius, Dominik and Seefeldt, Patric and Venditti, Flaviane c. F. and Vergaaij, Merel and Viavattene, Giulia and Virkki, Anne K. and Zander, Martin}, title = {More bucks for the bang: new space solutions, impact tourism and one unique science \& engineering opportunity at T-6 months and counting}, series = {7th IAA Planetary Defense Conference}, booktitle = {7th IAA Planetary Defense Conference}, year = {2021}, abstract = {For now, the Planetary Defense Conference Exercise 2021's incoming fictitious(!), asteroid, 2021 PDC, seems headed for impact on October 20th, 2021, exactly 6 months after its discovery. Today (April 26th, 2021), the impact probability is 5\%, in a steep rise from 1 in 2500 upon discovery six days ago. We all know how these things end. Or do we? Unless somebody kicked off another headline-grabbing media scare or wants to keep civil defense very idle very soon, chances are that it will hit (note: this is an exercise!). Taking stock, it is barely 6 months to impact, a steadily rising likelihood that it will actually happen, and a huge uncertainty of possible impact energies: First estimates range from 1.2 MtTNT to 13 GtTNT, and this is not even the worst-worst case: a 700 m diameter massive NiFe asteroid (covered by a thin veneer of Ryugu-black rubble to match size and brightness), would come in at 70 GtTNT. In down to Earth terms, this could be all between smashing fireworks over some remote area of the globe and a 7.5 km crater downtown somewhere. Considering the deliberate and sedate ways of development of interplanetary missions it seems we can only stand and stare until we know well enough where to tell people to pack up all that can be moved at all and save themselves. But then, it could just as well be a smaller bright rock. The best estimate is 120 m diameter from optical observation alone, by 13\% standard albedo. NASA's upcoming DART mission to binary asteroid (65803) Didymos is designed to hit such a small target, its moonlet Dimorphos. The Deep Impact mission's impactor in 2005 successfully guided itself to the brightest spot on comet 9P/Tempel 1, a relatively small feature on the 6 km nucleus. And 'space' has changed: By the end of this decade, one satellite communication network plans to have launched over 11000 satellites at a pace of 60 per launch every other week. This level of series production is comparable in numbers to the most prolific commercial airliners. Launch vehicle production has not simply increased correspondingly - they can be reused, although in a trade for performance. Optical and radio astronomy as well as planetary radar have made great strides in the past decade, and so has the design and production capability for everyday 'high-tech' products. 60 years ago, spaceflight was invented from scratch within two years, and there are recent examples of fast-paced space projects as well as a drive towards 'responsive space'. It seems it is not quite yet time to abandon all hope. We present what could be done and what is too close to call once thinking is shoved out of the box by a clear and present danger, to show where a little more preparedness or routine would come in handy - or become decisive. And if we fail, let's stand and stare safely and well instrumented anywhere on Earth together in the greatest adventure of science.}, language = {en} } @inproceedings{SchmidtKaschEichleretal.2021, author = {Schmidt, Thomas and Kasch, Susanne and Eichler, Fabian and Thurn, Laura}, title = {Process strategies on laser-based melting of glass powder}, series = {LiM 2021 proceedings}, booktitle = {LiM 2021 proceedings}, pages = {10 Seiten}, year = {2021}, abstract = {This paper presents the laser-based powder bed fusion (L-PBF) using various glass powders (borosilicate and quartz glass). Compared to metals, these require adapted process strategies. First, the glass powders were characterized with regard to their material properties and their processability in the powder bed. This was followed by investigations of the melting behavior of the glass powders with different laser wavelengths (10.6 µm, 1070 nm). In particular, the experimental setup of a CO2 laser was adapted for the processing of glass powder. An experimental setup with integrated coaxial temperature measurement/control and an inductively heatable build platform was created. This allowed the L-PBF process to be carried out at the transformation temperature of the glasses. Furthermore, the component's material quality was analyzed on three-dimensional test specimen with regard to porosity, roughness, density and geometrical accuracy in order to evaluate the developed L-PBF parameters and to open up possible applications.}, language = {en} } @article{BlankeHagenkampDoeringetal.2021, author = {Blanke, Tobias and Hagenkamp, Markus and D{\"o}ring, Bernd and G{\"o}ttsche, Joachim and Reger, Vitali and Kuhnhenne, Markus}, title = {Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates}, series = {Geothermal Energy}, volume = {9}, journal = {Geothermal Energy}, number = {Article number: 19}, publisher = {Springer}, address = {Berlin}, issn = {2195-9706}, doi = {10.1186/s40517-021-00201-3}, pages = {23 Seiten}, year = {2021}, abstract = {Previous studies optimized the dimensions of coaxial heat exchangers using constant mass fow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar fow types. In contrast, in this study, fow conditions in the circular ring are kept constant (a set of fxed Reynolds numbers) during optimization. This approach ensures fxed fow conditions and prevents inappropriately high or low mass fow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic efort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass fow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellstr{\"o}m's borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefcients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy diference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy fux and hydraulic efort. The Reynolds number in the circular ring is instead of the mass fow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54\% of the outer pipe radius for laminar fow and 60\% for turbulent fow scenarios. Net-exergetic optimization shows a predominant infuence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth's thermal properties and the fow type. Conclusively, coaxial geothermal probes' design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.}, language = {en} }