@article{FuchsHofzumahausRohreretal.2013, author = {Fuchs, H. and Hofzumahaus, A. and Rohrer, F. and Bohn, Birger and Brauers, Theo and Dorn, Hans-Peter and H{\"a}seler, R. and Holland, F. and Kaminski, M. and Li, X. and Lu, K. and Nehr, Sascha and Tillmann, R. and Wegener, R. and Wahner, A.}, title = {Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation}, series = {Nature Geoscience}, volume = {6}, journal = {Nature Geoscience}, number = {12}, publisher = {Springer Nature}, issn = {1752-0894}, doi = {10.1038/NGEO1964}, pages = {1023 -- 1026}, year = {2013}, language = {en} } @article{FuchsDornBachneretal.2012, author = {Fuchs, H. and Dorn, Hans-Peter and Bachner, M. and Bohn, Birger and Brauers, Theo and Gomm, S. and Hofzumahaus, A. and Holland, F. and Nehr, Sascha and Rohrer, F. and Tillmann, R. and Wahner, A.}, title = {Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration}, series = {Atmospheric Measurement Techniques}, volume = {5}, journal = {Atmospheric Measurement Techniques}, number = {7}, publisher = {Copernicus}, issn = {1867-8548}, doi = {10.5194/amt-5-1611-2012}, pages = {1611 -- 1626}, year = {2012}, abstract = {Abstract. During recent field campaigns, hydroxyl radical (OH) concentrations that were measured by laser-induced fluorescence (LIF) were up to a factor of ten larger than predicted by current chemical models for conditions of high OH reactivity and low NO concentration. These discrepancies, which were observed in forests and urban-influenced rural environments, are so far not entirely understood. In summer 2011, a series of experiments was carried out in the atmosphere simulation chamber SAPHIR in J{\"u}lich, Germany, in order to investigate the photochemical degradation of isoprene, methyl-vinyl ketone (MVK), methacrolein (MACR) and aromatic compounds by OH. Conditions were similar to those experienced during the PRIDE-PRD2006 campaign in the Pearl River Delta (PRD), China, in 2006, where a large difference between OH measurements and model predictions was found. During experiments in SAPHIR, OH was simultaneously detected by two independent instruments: LIF and differential optical absorption spectroscopy (DOAS). Because DOAS is an inherently calibration-free technique, DOAS measurements are regarded as a reference standard. The comparison of the two techniques was used to investigate potential artifacts in the LIF measurements for PRD-like conditions of OH reactivities of 10 to 30 s-1 and NO mixing ratios of 0.1 to 0.3 ppbv. The analysis of twenty experiment days shows good agreement. The linear regression of the combined data set (averaged to the DOAS time resolution, 2495 data points) yields a slope of 1.02 ± 0.01 with an intercept of (0.10 ± 0.03) × 106 cm-3 and a linear correlation coefficient of R2 = 0.86. This indicates that the sensitivity of the LIF instrument is well-defined by its calibration procedure. No hints for artifacts are observed for isoprene, MACR, and different aromatic compounds. LIF measurements were approximately 30-40\% (median) larger than those by DOAS after MVK (20 ppbv) and toluene (90 ppbv) had been added. However, this discrepancy has a large uncertainty and requires further laboratory investigation. Observed differences between LIF and DOAS measurements are far too small to explain the unexpected high OH concentrations during the PRIDE-PRD2006 campaign.}, language = {en} } @article{FuchsBohnHofzumahausetal.2011, author = {Fuchs, H. and Bohn, Birger and Hofzumahaus, A. and Holland, F. and Lu, K. D. and Nehr, Sascha and Rohrer, F. and Wahner, A.}, title = {Detection of HO2 by laser-induced fluorescence: calibration and interferences from RO2 radicals}, series = {Atmospheric Measurement Techniques}, volume = {4}, journal = {Atmospheric Measurement Techniques}, number = {6}, publisher = {Copernicus}, issn = {1867-8548}, doi = {10.5194/amt-4-1209-2011}, pages = {1209 -- 1225}, year = {2011}, abstract = {Abstract. HO2 concentration measurements are widely accomplished by chemical conversion of HO2 to OH including reaction with NO and subsequent detection of OH by laser-induced fluorescence. RO2 radicals can be converted to OH via a similar radical reaction sequence including reaction with NO, so that they are potential interferences for HO2 measurements. Here, the conversion efficiency of various RO2 species to HO2 is investigated. Experiments were conducted with a radical source that produces OH and HO2 by water photolysis at 185 nm, which is frequently used for calibration of LIF instruments. The ratio of HO2 and the sum of OH and HO2 concentrations provided by the radical source was investigated and was found to be 0.50 ± 0.02. RO2 radicals are produced by the reaction of various organic compounds with OH in the radical source. Interferences via chemical conversion from RO2 radicals produced by the reaction of OH with methane and ethane (H-atom abstraction) are negligible consistent with measurements in the past. However, RO2 radicals from OH plus alkene- and aromatic-precursors including isoprene (mainly OH-addition) are detected with a relative sensitivity larger than 80 \% with respect to that for HO2 for the configuration of the instrument with which it was operated during field campaigns. Also RO2 from OH plus methyl vinyl ketone and methacrolein exhibit a relative detection sensitivity of 60 \%. Thus, previous measurements of HO2 radical concentrations with this instrument were biased in the presence of high RO2 radical concentrations from isoprene, alkenes or aromatics, but were not affected by interferences in remote clean environment with no significant emissions of biogenic VOCs, when the OH reactivity was dominated by small alkanes. By reducing the NO concentration and/or the transport time between NO addition and OH detection, interference from these RO2 species are suppressed to values below 20 \% relative to the HO2 detection sensitivity. The HO2 conversion efficiency is also smaller by a factor of four, but this is still sufficient for atmospheric HO2 concentration measurements for a wide range of conditions.}, language = {en} } @article{FuchsAcirBohnetal.2014, author = {Fuchs, H. and Acir, Ismail-Hakki and Bohn, Birger and Brauers, Theo and Dorn, Hans-Peter and H{\"a}seler, R. and Hofzumahaus, A. and Holland, F. and Kaminski, M. and Li, X. and Lu, K. and Lutz, A. and Nehr, Sascha and Rohrer, F. and Tillmann, R. and Wegener, R. and Wahner, A.}, title = {OH regeneration from methacrolein oxidation investigated in the atmosphere simulation chamber SAPHIR}, series = {Atmospheric Chemistry and Physics}, volume = {14}, journal = {Atmospheric Chemistry and Physics}, number = {15}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-14-7895-2014}, pages = {7895 -- 7908}, year = {2014}, abstract = {Abstract. Hydroxyl radicals (OH) are the most important reagent for the oxidation of trace gases in the atmosphere. OH concentrations measured during recent field campaigns in isoprene-rich environments were unexpectedly large. A number of studies showed that unimolecular reactions of organic peroxy radicals (RO2) formed in the initial reaction step of isoprene with OH play an important role for the OH budget in the atmosphere at low mixing ratios of nitrogen monoxide (NO) of less than 100 pptv. It has also been suggested that similar reactions potentially play an important role for RO2 from other compounds. Here, we investigate the oxidation of methacrolein (MACR), one major oxidation product of isoprene, by OH in experiments in the simulation chamber SAPHIR under controlled atmospheric conditions. The experiments show that measured OH concentrations are approximately 50\% larger than calculated by the Master Chemical Mechanism (MCM) for conditions of the experiments (NO mixing ratio of 90 pptv). The analysis of the OH budget reveals an OH source that is not accounted for in MCM, which is correlated with the production rate of RO2 radicals from MACR. In order to balance the measured OH destruction rate, 0.77 OH radicals (1σ error: ± 0.31) need to be additionally reformed from each reaction of OH with MACR. The strong correlation of the missing OH source with the production of RO2 radicals is consistent with the concept of OH formation from unimolecular isomerization and decomposition reactions of RO2. The comparison of observations with model calculations gives a lower limit of 0.03 s-1 for the reaction rate constant if the OH source is attributed to an isomerization reaction of MACR-1-OH-2-OO and MACR-2-OH-2-OO formed in the MACR + OH reaction as suggested in the literature (Crounse et al., 2012). This fast isomerization reaction would be a competitor to the reaction of this RO2 species with a minimum of 150 pptv NO. The isomerization reaction would be the dominant reaction pathway for this specific RO2 radical in forested regions, where NO mixing ratios are typically much smaller.}, language = {en} } @inproceedings{FriedrichRuessSchroeder2016, author = {Friedrich, Linus and Ruess, Martin and Schr{\"o}der, Kai-Uwe}, title = {Efficient and robust shell design of space launcher vehicle structures}, series = {57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, San Diego, 4-8 January 2016}, booktitle = {57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, San Diego, 4-8 January 2016}, publisher = {American Institute of Aeronautics and Astronautics}, address = {Reston}, isbn = {978-1-62410-392-6}, doi = {10.2514/6.2016-1973}, pages = {1 -- 18}, year = {2016}, language = {en} } @inproceedings{FriedrichLyssakowPearceetal.2016, author = {Friedrich, Linus and Lyssakow, Pawel and Pearce, Garth and Ruess, Martin and Bisagni, Chiara and Schr{\"o}der, Kai-Uwe}, title = {ON THE STRUCTURAL DESIGN OF IMPERFECTION SENSITIVE LAMINATED COMPOSITE SHELL STRUCTURES SUBJECTED TO AXIAL COMPRESSION}, series = {Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016), 05.06.2016 - 10.06.2016, Crete Island}, booktitle = {Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016), 05.06.2016 - 10.06.2016, Crete Island}, editor = {Papadrakakis, Manolis and Papadopoulos, V. and Stefanou, G. and Plevris, V.}, publisher = {Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece}, address = {Athens}, isbn = {978-618-82844-0-1}, doi = {10.7712/100016.1951.5838}, pages = {2182 -- 2189}, year = {2016}, language = {en} } @article{FriedrichLoosenLiangetal.2015, author = {Friedrich, Linus and Loosen, Simon and Liang, Ke and Ruess, Martin and Bisagni, Chiara and Schr{\"o}der, Kai-Uwe}, title = {Stacking sequence influence on imperfection sensitivity of cylindrical composite shells under axial compression}, series = {Composite Structures}, volume = {134}, journal = {Composite Structures}, publisher = {Elsevier}, issn = {0263-8223}, doi = {10.1016/j.compstruct.2015.08.132}, pages = {750 -- 761}, year = {2015}, language = {en} } @inproceedings{FranzStaabArndt2007, author = {Franz, Thomas and Staab, Steffen and Arndt, Richard}, title = {The X-COSIM integration framework for a seamless semantic desktop}, series = {Proceedings of the 4th international conference on Knowledge capture}, booktitle = {Proceedings of the 4th international conference on Knowledge capture}, editor = {Sleeman, Derek and Barker, Ken}, publisher = {ACM}, address = {New York, NY}, isbn = {978-1-59593-643-1}, doi = {10.1145/1298406.1298433}, pages = {143}, year = {2007}, language = {en} } @inproceedings{FranzStaab2005, author = {Franz, Thomas and Staab, Steffen}, title = {SAM: Semantics Aware Instant Messaging for the Networked Semantic Desktop. revised and extended version}, series = {Proceedings of the 1st Workshop On The Semantic Desktop. 4th International Semantic Web Conference}, booktitle = {Proceedings of the 1st Workshop On The Semantic Desktop. 4th International Semantic Web Conference}, editor = {Decker, Stefan and Park, Jack and Quan, Dennis and Sauermann, Leo}, address = {Galway}, pages = {1 -- 15}, year = {2005}, language = {en} } @incollection{FranzSizov2008, author = {Franz, Thomas and Sizov, Sergej}, title = {Communication Systems for Semantic Work Environments}, series = {Emerging Technologies for Semantic Work Environments}, booktitle = {Emerging Technologies for Semantic Work Environments}, editor = {Rech, J{\"o}rg and Decker, Bj{\"o}rn and Ras, Eric}, publisher = {IGI Global}, address = {Hershey}, doi = {10.4018/978-1-59904-877-2.ch002}, pages = {16 -- 32}, year = {2008}, language = {en} }