State-space realization of a describing function

The describing function is a powerful tool for characterizing nonlinear dynamical systems in the frequency domain. In some cases, it is the only available description of a nonlinear operator characterizing a certain subcomponent of the system. This paper presents a methodology to provide a state-space realization of one given describing function, in order to allow the study of the system in the time domain as well. The realization is based on Hammerstein models and Fourier–Bessel series. It can be embedded in time domain simulations of complex configurations with many nonlinear elements interacting, accurately describing the nonlinear saturation of the system. The technique is applied to an example application in the field of combustion instability, featuring self-excited thermoacoustic oscillations. We benchmark the performance of the tool comparing the results with a frequency domain analysis of the same system, obtaining good agreement between the two formulations.This work was supported by the European Research Council through project ALORS N.259620 and by the German Research Association for Combustion Engines (Forschungsvereinigung Verbrennungskraftmaschinen e.V. FVV).This is the accepted manuscript of a paper published in Nonlinear Dynamics (Ghirardo G, Ćosić B, Juniper MP, Moeck JP, Nonlinear Dynamics, 2015, doi:10.1007/s11071-015-2134-x). The final version is available at http://dx.doi.org/10.1007/s11071-015-2134-

Studies of plant terpenoid biosynthesis using 13C stable isotope labeling techniques (KIT Scientific Reports ; 7583)

This thesis aims to deepen our understanding of plant terpenoid biosynthesis and the regulation of the 2-C-methylerythritol-4-phosphate pathway (MEP) with respect to isoprene and monoterpene biosynthesis in plant. For this purposes, stable isotope techniques were employed, providing information on the carbon sources for terpenoids biosynthesis and C fluxes within the MEP pathway at various spatial and temporal scales, as well as giving insight into the regulation of enzymes from the MEP pathway

NBA Salaries: Assessing True Player Value

This paper analyzes and calculates an advanced NBA statistic that is becoming more and more widely used in the NBA. The Adjusted plus-minus (APM) statistic measures a player’s contribution, independent of all other players on the court. The most appealing aspect to the APM is that it only attempts to capture how a team’s scoring margin changes with a particular player on and off the court. Scoring margin in basketball effects winning percentage greatly, so it only makes sense that players with high APM’s will increase their team’s scoring margin and, therefore, help win games. The APM statistic is not an exhaustive approach to finding NBA talent. Many quantitative and qualitative factors, in addition to the APM, should be investigated before acquiring a player. However, the APM needs to be addressed and carefully examined along with these other factors. In any sport, basketball included, it is natural (and human) for experts to just believe what they see. However, much of what NBA scouts and upper-management see they subconsciously over or under-value, and that can lead to errant judgments. Paying an average or below average player way too much can be a huge mistake to an NBA franchise. Therefore, a comprehensive in-depth analysis must be conducted both statistically (with traditional and advanced measures) as well as visually. The APM statistic is growing quickly in popularity as a quantitative tool, and will continue to do so, because it measures better than anything else presently something that is critically important; how much does a player actually contribute to team success? Armed with this “arrow” in his quiver, the smart GM can make more informed personnel decisions for his team by more effienctly allocating his limited resources. Some possible very under-valued players are examined in this paper that could potentially help a GM make better decisions. This in turn will maximize his chances of building a winning team over time

Ferrarese Chronicles in the Modern Era

En 1928, Giuseppe Pardi va publicar la primera de tres cròniques del segle XV sobre Ferrara. La seua edició d'un d'aquestes tres cròniques, el Diari ferrarese dall?anno 1409 sinó al 1502, va substituir versió del segle XVIII publicada per Ludovico Muratori. Pardi va mostrar una comprensió dels reptes que presenta la transcripció de documents antics, refusant alterar aquest material i enriquint les cròniques amb un aparell crític complet. Malgrat la disponibilitat i fàcil accés a materials inimaginables fins fa poc, les transcripcions de finals del segle XX no arriben als estàndards establerts per Pardi. Aquest article explora les transcripcions de les cròniques, en particular les de Pardi, il·lustrant com els inicis del segle XX van ser una època daurada sense igual abans o després

Travels in Architectural History

Travel is a powerful force in shaping the perception of the modern world and plays an ever-growing role within architectural and urban cultures. Inextricably linked to political and ideological issues, travel redefines places and landscapes through new transport infrastructures and buildings. Architecture, in turn, is reconstructed through visual and textual narratives produced by scores of modern travellers — including writers and artists along with architects themselves. In the age of the camera, travel is bound up with new kinds of imaginaries; private records and recollections often mingle with official, stereotyped views, as the value of architectural heritage increasingly rests on the mechanical reproduction of its images. Whilst students often learn about architectural history through image collections, the place of the journey in the formation of the architect itself shifts. No longer a lone and passionate antiquarian or an itinerant designer, the modern architect eagerly hops on buses, trains, and planes in pursuit of personal as well as professional interests. Increasingly built on a presumption of mobility, architectural culture integrates travel into cultural debates and design experiments. By addressing such issues from a variety of perspectives, this collection, a special Architectural Histories issue on travel, prompts us to rethink the mobile conditions in which architecture has historically been produced and received

Azimuthal flame response and symmetry breaking in a forced annular combustor

In the current study azimuthal forcing of an annular combustor with swirling flames has been performed to present for the first time the Heat Release Rate (HRR) response to all possible pressure fields of the first azimuthal mode up to a finite amplitude limit. The response is first quantified through the conventional Flame Describing Function (FDF) framework, showing a difference in response which depends on whether the acoustic field rotates anti-clockwise or clockwise, albeit with some scatter. Additionally and somewhat surprisingly, a finite HRR response is observed for flames exactly in the pressure node. An Azimuthal FDF is introduced, based on the decomposition of the spatial HRR response through Bloch theory, to better highlight the difference in HRR response to the anti-clockwise and clockwise components of the acoustic field and reduce scatter. A clear difference in response is observed, with a significantly higher response to the anti-clockwise forcing component compared to the clockwise component, independent of the prescribed pressure mode. The difference is attributed to the systematic symmetry breaking introduced by using an annular enclosure of finite curvature and width with swirling flames. It is argued that the finite curvature and width of the geometry and the swirl need to be both present to observe this effect. The difference in response results in a difference between the nature angle of the HRR mode and that of the acoustic field, explaining the relatively large HRR response observed for flames in the pressure node. The Azimuthal FDF describe all of these phenomena well, and is therefore considered more suitable than the conventional FDF to characterise the response in an annular combustor.publishedVersion© 2021 The Author(s). Published by Elsevier Inc. on behalf of The Combustion Institute. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/

Saturation of flames to multiple inputs at one frequency

Existing experimental results show that swirling flames in annular combustors respond with a different gain to acoustic azimuthal modes rotating in either the clockwise or anti-clockwise direction. The ratio R of these two gains is introduced, with R=1 being the conventional case of flames responding the same to the two forcing directions. To allow a difference in response to the different directions (R≠1), a multiple-input single-output azimuthal flame describing function is successfully implemented in a quaternion valued low-order model of an annular combustion chamber in the current work. Theoretical studies have explored this kind of symmetry breaking between the two acoustic wave directions in the past, but it has not been backed by experimental data. One of the main features of the new model proposed in this work is the potential difference in mode shapes between the acoustic and the heat release rate modes, which has recently been observed experimentally. This results in a gain-dependent equation for the nature of the mode, which has a significant influence on the fixed points of the system. For example, one of the spinning solutions and the standing solution can disappear through a saddle node bifurcation as the parameters are varied. The presence of only a single direction for the spinning solution matches experimental observations better than the conventional models, and the proposed model is shown to qualitatively describe experimental measurements well.publishedVersio