4,064 research outputs found
Evaluation of different methods for determining the angle of attack on wind turbine blades with CFD results under axial inflow conditions
This work presents an investigation on different methods for the calculation
of the angle of attack and the underlying induced velocity on wind turbine
blades using data obtained from three-dimensional Computational Fluid Dynamics
(CFD). Several methods are examined and their advantages, as well as
shortcomings, are presented. The investigations are performed for two 10MW
reference wind turbines under axial inflow conditions, namely the turbines
designed in the EU AVATAR and INNWIND.EU projects. The results show that the
evaluated methods are in good agreement with each other at the mid-span, though
some deviations are observed at the root and tip regions of the blades. This
indicates that CFD results can be used for the calibration of induction
modeling for Blade Element Momentum (BEM) tools. Moreover, using any of the
proposed methods, it is possible to obtain airfoil characteristics for lift and
drag coefficients as a function of the angle of attack.Comment: This manuscript is Accepted at at Renewable Energy journal- online 13
March 2018 under the CC-BY-NC-ND 4.0 licens
The Code of Protest. Images of Peace in the West German Peace Movements, 1945-1990
The article examines posters produced by the peace movements in the Federal Republic of
Germany during the ColdWar, with an analytical focus on the transformation of the iconography
of peace in modernity. Was it possible to develop an independent, positive depiction of peace
in the context of protests for peace and disarmament? Despite its name, the pictorial selfrepresentation
of the campaign âFight against Nuclear Deathâ in the late 1950s did not draw
on the theme of pending nuclear mass death. The large-scale protest movement in the 1980s
against NATOâs 1979 âdouble-trackâ decision contrasted female peacefulness with masculine
aggression in an emotionally charged pictorial symbolism. At the same time this symbolism
marked a break with the pacifist iconographic tradition that had focused on the victims of war.
Instead, the movement presented itself with images of demonstrating crowds, as an anticipation
of its peaceful ends. Drawing on the concept of asymmetrical communicative âcodesâ that has
been developed in sociological systems theory, the article argues that the iconography of peace in
peace movement posters could not develop a genuinely positive vision of peace, since the code of
protest can articulate the designation value âpeaceâ only in conjunction with the rejection value
âwarâ
The sigh of the oppressed: The palliative effects of ideology are stronger for people living in highly unequal neighbourhoods
Ideologies that legitimise status hierarchies are associated with increased wellbeing. However, which ideologies have âpalliative effectsâ, why they have these effects, and whether these effects extend to low-status groups remain unresolved issues. The present study aimed to address these issues by testing the effects of the ideology of Symbolic Prejudice on wellbeing among low- and high-status ethnic groups (4,519 Europeans and 1,091 MÄori) nested within 1,437 regions in New Zealand. Results showed that Symbolic Prejudice predicted increased wellbeing for both groups, but that this relationship was stronger for those living in highly unequal neighbourhoods. This suggests that it is precisely those who have the strongest need to justify inequality that accrue the most psychological benefit from subscribing to legitimising ideologies
Minimizing attosecond CEP jitter by carrier envelope phase tuning
Minimizing the CEP jitter of isolated attosecond pulses (IAP) will be important for future applications. This jitter is experimentally and theoretically investigated and can be minimized when the driving pulse is near its Fourier limit but with slightly negative chirp. Thus, understanding and characterization of the CEP jitter of IAPs is a first step towards exact control of the electric field of IAP pulses
Exploring small-scale chemostats to scale up microbial processes: 3-hydroxypropionic acid production in S. cerevisiae
Abstract Background The physiological characterization of microorganisms provides valuable information for bioprocess development. Chemostat cultivations are a powerful tool for this purpose, as they allow defined changes to one single parameter at a time, which is most commonly the growth rate. The subsequent establishment of a steady state then permits constant variables enabling the acquisition of reproducible data sets for comparing microbial performance under different conditions. We performed physiological characterizations of a 3-hydroxypropionic acid (3-HP) producing Saccharomyces cerevisiae strain in a miniaturized and parallelized chemostat cultivation system. The physiological conditions under investigation were various growth rates controlled by different nutrient limitations (C, N, P). Based on the cultivation parameters obtained subsequent fed-batch cultivations were designed. Results We report technical advancements of a small-scale chemostat cultivation system and its applicability for reliable strain screening under different physiological conditions, i.e. varying dilution rates and different substrate limitations (C, N, P). Exploring the performance of an engineered 3-HP producing S. cerevisiae strain under carbon-limiting conditions revealed the highest 3-HP yields per substrate and biomass of 16.6 %C-mol and 0.43 g gCDWâ1, respectively, at the lowest set dilution rate of 0.04 hâ1. 3-HP production was further optimized by applying N- and P-limiting conditions, which resulted in a further increase in 3-HP yields revealing values of 21.1 %C-mol and 0.50 g gCDWâ1 under phosphate-limiting conditions. The corresponding parameters favoring an increased 3-HP production, i.e. dilution rate as well as C- and P-limiting conditions, were transferred from the small-scale chemostat cultivation system to 1-L bench-top fermenters operating in fed-batch conditions, revealing 3-HP yields of 15.9 %C-mol and 0.45 g gCDWâ1 under C-limiting, as well as 25.6 %C-mol and 0.50 g gCDWâ1 under phosphate-limiting conditions. Conclusions Small-scale chemostat cultures are well suited for the physiological characterization of microorganisms, particularly for investigating the effect of changing cultivation parameters on microbial performance. In our study, optimal conditions for 3-HP production comprised (i) a low dilution rate of 0.04 hâ1 under carbon-limiting conditions and (ii) the use of phosphate-limiting conditions. Similar 3-HP yields were achieved in chemostat and fed-batch cultures under both C- and P-limiting conditions proving the growth rate as robust parameter for process transfer and thus the small-scale chemostat system as powerful tool for process optimization
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