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- ItemSynthesis of flow‐compatible Ru-Me/Al2O3 catalysts and their application in hydrogenation of 1-iodo-4-nitrobenzene([Cham] : Springer International Publishing, 2021) Sebek, Michael; Atia, Hanan; Steinfeldt, NorbertThe development of an active, selective, and long-term stable heterogeneous catalyst for the reductive hydrogenation of substituted nitrorarenes in continuous operation mode is still challenging. In this work, Ru based nanoparticles catalysts promoted with different transition metals (Zn, Co, Cu, Sn, or Fe) were supported on alumina spheres using spray wet impregnation method. The freshly prepared catalysts were characterized using complementary methods including scanning transmission electron microscopy (STEM) and temperature programmed reduction (TPR). The hydrogenation of 1-iodo-4-nitrobenzene served as model reaction to assess the catalytic performance of the prepared catalysts. The addition of the promotor affected the reducibility of Ru nanoparticles as well as the performance of the catalyst in the hydrogenation reaction. The highest yield of 4-iodoaniline (89 %) was obtained in a continuous flow process using Ru-Sn/Al2O3. The performance of this catalyst was also followed in a long-term experiment. With increasing operation time, a catalyst deactivation occurred which could only briefly compensate by an increase of the reaction temperature.
- ItemTopology of products similarity network for market forecasting([Cham] : Springer International Publishing, 2019) Fan, Jingfang; Cohen, Keren; Shekhtman, Louis M.; Liu, Sibo; Meng, Jun; Louzoun, Yoram; Havlin, ShlomoThe detection and prediction of risk in financial markets is one of the main challenges of economic forecasting, and draws much attention from the scientific community. An even more challenging task is the prediction of the future relative gain of companies. We here develop a novel combination of product text analysis, network theory and topological based machine learning to study the future performance of companies in financial markets. Our network links are based on the similarity of firms’ products and constructed using the Securities Exchange Commission (SEC) filings of US listed firms. We find that several topological features of this network can serve as good precursors of risks or future gain of companies. We then apply machine learning to network attributes vectors for each node to predict successful and failing firms. The resulting accuracies are much better than current state of the art techniques. The framework presented here not only facilitates the prediction of financial markets but also provides insight and demonstrates the power of combining network theory and topology based machine learning.
- ItemMeridionally Extending Anomalous Wave Train over Asia During Breaks in the Indian Summer Monsoon([Cham] : Springer International Publishing, 2019) Umakanth, Uppara; Vellore, Ramesh K.; Krishnan, R.; Choudhury, Ayantika Dey; Bisht, Jagat S.H.; Di Capua, Giorgia; Coumou, Dim; Donner, Reik V.Anomalous interactions between the Indian summer monsoon (ISM) circulation and subtropical westerlies are known to trigger breaks in the ISM on subseasonal time-scales, characterised by a pattern of suppressed rainfall over central-north India, and enhanced rainfall over the foothills of the central–eastern Himalayas (CEH). An intriguing feature during ISM breaks is the formation of a mid-tropospheric cyclonic circulation anomaly extending over the subtropical and mid-latitude areas of the Asian continent. This study investigates the mechanism of the aforesaid Asian continental mid-tropospheric cyclonic circulation (ACMCC) anomaly using observations and simplified model experiments. The results of our study indicate that the ACMCC during ISM breaks is part of a larger meridional wave train comprising of alternating anticyclonic and cyclonic anomalies that extend poleward from the monsoon region to the Arctic. A lead–lag analysis of mid-tropospheric circulation anomalies suggests that the meridional wave-train generation is linked to latent heating (LH) anomalies over the CEH foothills, Indo-China, and the Indian landmass during ISM breaks. By conducting sensitivity experiments using a simplified global atmospheric general circulation model forced with satellite-derived three-dimensional LH, it is demonstrated that the combined effects of the enhanced LH over the CEH foothills and Indo-China and decreased LH over the Indian landmass during ISM breaks are pivotal for generating the poleward extending meridional wave train and the ACMCC anomaly. At the same time, the spatial extent of the mid-latitude cyclonic anomaly over Far-East Asia is also influenced by the anomalous LH over central–eastern China. While the present findings provide interesting insights into the role of LH anomalies during ISM breaks on the poleward extending meridional wave train, the ACMCC anomaly is found to have important ramifications on the daily rainfall extremes over the Indo-China region. It is revealed from the present analysis that the frequency of extreme rainfall occurrences over Indo-China shows a twofold increase during ISM break periods as compared to active ISM conditions. © 2019, The Author(s).
- ItemAdditive Manufacturing of Binary Ni–Ti Shape Memory Alloys Using Electron Beam Powder Bed Fusion: Functional Reversibility Through Minor Alloy Modification and Carbide Formation([Cham] : Springer International Publishing, 2022) Krooß, P.; Lauhoff, C.; Gustmann, T.; Gemming, T.; Sobrero, C.; Ewald, F.; Brenne, F.; Arold, T.; Nematolahi, M.; Elahinia, M.; Thielsch, J.; Hufenbach, J.; Niendorf, T.Shape memory alloys (SMAs), such as Ni–Ti, are promising candidates for actuation and damping applications. Although processing of Ni–Ti bulk materials is challenging, well-established processing routes (i.e. casting, forging, wire drawing, laser cutting) enabled application in several niche applications, e.g. in the medical sector. Additive manufacturing, also referred to as 4D-printing in this case, is known to be highly interesting for the fabrication of SMAs in order to produce near-net-shaped actuators and dampers. The present study investigated the impact of electron beam powder bed fusion (PBF-EB/M) on the functional properties of C-rich Ni50.9Ti49.1 alloy. The results revealed a significant loss of Ni during PBF-EB/M processing. Process microstructure property relationships are discussed in view of the applied master alloy and powder processing route, i.e. vacuum induction-melting inert gas atomization (VIGA). Relatively high amounts of TiC, being already present in the master alloy and powder feedstock, are finely dispersed in the matrix upon PBF-EB/M. This leads to a local change in the chemical composition (depletion of Ti) and a pronounced shift of the transformation temperatures. Despite the high TiC content, superelastic testing revealed a good shape recovery and, thus, a negligible degradation in both, the as-built and the heat-treated state.