| 1. |
- Hochreiner, Georg, et al.
(author)
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The Historic Roof Structure of the Spanish Riding School in Vienna : Structural Assessment
- 2015
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In: Proceedings of the International Conference on Structural Health Assessment of Timber Structures, SHATIS15. - : Dolnoslaskie Wydawnictwo Edukacyjne (DWE). - 9788371252563 ; , s. 248-259
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Conference paper (peer-reviewed)abstract
- In 2012, the historical roof structure of the Spanish Riding School, built in the years from 1729 to 1735 as part of the ensemble of the Vienna Imperial Palace (called Hofburg), was documented by students and staff of the Vienna University of Technology. The survey was performed deformation- accurate and included both, the main structure and corresponding joints. Consequently, the documentation highlights deviations from the initial perception of the roof structure such as broken joints, inactivity of compressive devices like knee braces or excessive displacements of single structural members. Probably, these damages led to strengthening measures (=additional substructures) that were added in recent times to avoid progressive failure. This documentation formed the basis for the assessment of this historical roof structure from a structural and timber engineering point of view, which will be presented herein. The focus of the structural modelling was placed on the assessment of the two initial structural concepts, namely the main hall with and without the timber dome structure that was added in 1734, by visualisation of the internal forces and displacements. For this purpose, the nonlinear load carrying capacities and failure modes of the carpentry joints were assessed. Subsequently, alternative structural systems could be found by iterative recalculation revealing the capabilities for redundancy of the timber roof structure. Corresponding results were checked again with in-situ observations. Consequently, the findings of this study highlight the benefits of integrating modern structural and timber engineering methods and tools in the context of building history and building survey.
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| 2. |
- Yao, Dawei, 1991, et al.
(author)
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Deciphering SO2 poisoning mechanisms for passive NOx adsorption: A kinetic modeling approach and development of a high-resistance catalyst
- 2024
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In: Chemical Engineering Journal. - 1385-8947. ; 487
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Journal article (peer-reviewed)abstract
- Passive NOx adsorption (PNA) is a promising technology aimed at reducing NOx emissions from vehicles during the cold start phase of the engine. This work investigated the SO2 poisoning mechanism of PNA through a combination of experimental research and kinetic modeling, leading to the development of a novel PNA sample with high resistance to SO2 poisoning. Pd/SSZ-13 samples were synthesized using different drying conditions, revealing that samples dried at room temperature showed lower degradation (10 %) compared to those dried at 80 °C (26 %). Investigation into the degradation revealed that ion-exchanged Pd sites with a hydroxyl group were more resistant to SO2 poisoning than other Pd sites. It is also found that SO2 aids in NOx storage on Pd sites, enhancing the PNA performance. A kinetic model was developed to describe the SO2 poisoning behavior and its influence on NOx storage. The model, which was verified under various conditions, effectively simulated the PNA behavior and SO2 poisoning of Pd/SSZ-13.
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| 3. |
- Yao, Dawei, 1991, et al.
(author)
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Enhanced CO resistance of Pd/SSZ-13 for passive NOx adsorption
- 2023
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 460
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Journal article (peer-reviewed)abstract
- Passive NOx adsorption (PNA) is a novel technology to control NOx emissions during cold start. However, the recent generation of PNA material, Pd/zeolite, suffers from major degradation under high CO concentrations. In this work, we developed a novel form of Pd/SSZ-13 by using a freeze-drying process after incipient wetness impregnation. This Pd/SSZ-13 showed a better stability than the sample synthesized by the common process. Several characterization measurements were conducted and it was found that the Pd sites on the freeze-dried sample were more resistant towards CO-induced agglomeration. By combing in-situ characterization and kinetic modeling, we found that the freeze-dried Pd/SSZ-13 had more ion-exchanged Pd sites, which provided greater resistance towards the CO-induced Ostwald ripening process, and consequently suppressed the sintering behavior under a high CO concentration. This material offers a potentially improved stability of PNAs under extremely high CO concentration pulses from incomplete diesel combustion during engine cold start.
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| 4. |
- Yao, Dawei, 1991, et al.
(author)
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Insight into CO induced degradation mode of Pd/SSZ-13 in NOx adsorption and release: Experiment and modeling
- 2022
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 439
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Journal article (peer-reviewed)abstract
- Passive NOx adsorption (PNA) on Pd zeolites is an important technique to remove NOx during the cold start of the engine. However, the stability of Pd zeolites under high concentrations of CO is still challenging in multiple cold starts of an engine. Herein, we illustrate the CO-induced degradation mechanism of Pd zeolite by combining experiments and kinetic models. Pd/SSZ-13 has been used in multicycle processes containing NOx adsorption at low temperature and temperature programmed desorption, which represents the PNA degradation in multiple cold start periods. A kinetic model was developed to describe the NOx storage and degradation behavior of Pd/SSZ-13. Both experimental and modelling observations suggested that two Pd sintering modes are occurring under high CO concentration (4000 ppm), namely Ostwald ripening and particle migration. Apart from the degradation behavior, this model is also adequate for describing multi-cycle NOx storage and release behavior under low CO concentration.
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| 5. |
- Yao, Dawei, 1991, et al.
(author)
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Kinetic modeling of CO assisted passive NOx adsorption on Pd/SSZ-13
- 2022
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 428
-
Journal article (peer-reviewed)abstract
- Passive NOx adsorption (PNA) has been recently developed as a promising technology for controlling the NOx emissions during the cold start period. In this work, we illustrate a CO-assisted mechanism by combining experimental and kinetic modeling studies. Pd/SSZ-13 has been synthesized, characterized and evaluated as a PNA in low-temperature NOx adsorption and temperature program desorption cycles, to represent multiple cold start periods. The gas compositions were also systemically changed, where both the effect of varying NOx and CO feed was evaluated in the presence of high water and oxygen contents. A kinetic model was developed to simulate the profiles of NO and NO2, including three initial Pd sites (Z-Pd(II)Z-, Z-[Pd(II)OH]+ and PdO). It is concluded from XPS and in situ DRIFTS experiments, flow reactor measurements and modelling observations that CO reduces Pd(II) species to Pd(I)/Pd(0) species, which increases the stability of the stored NOx species, resulting in a release above the urea dosing temperature. The model could well describe the experimental features, including the effect of CO. In addition, the model was used for full-scale catalytic converter simulations.
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