Wyniki wyszukiwania - Biblioteka Nauki

1

On the implementation of viscoelastic models in commercial CFD programs

100%

Gruber M.

International Journal of Applied Mechanics and Engineering

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2005

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tom Vol. 10, no spec

219-224

EN

Although finite-volume methods have significant advantages in terms of memory usage and computational speed, traditionally finite-element based programs are used to solve complex viscoelastic fluid dynamic problems. This work presents the successful extension of the commercial, finite volume based, state-of-the-art CFD software package FLUENTŽ to viscoelastic fluid flow problems, a feature which is not supported by the standard version of the program. Differential viscoelastic models of Maxwell-Type are implemented utilizing two principle capabilities of the software, i.e. the possibilities to define additional transport equations for each component of the viscoelastic stress tensor and to modify this equations using the programming interface, respectively. Results of an illustrative benchmark problem are presented, demonstrating the capability and accuracy of the proposed method to perform viscoelastic flow simulations up to a Deborah number of 100.

2

Effects Of The Combined Heat And Cryogenic Treatment On The Stability Of Austenite In A High Co-Ni Steel

38%

Gruber M. , Ploberger S. , Ressel G. , Wiessner M. , Hausbauer M. , Marsoner S. , Ebner R.

Archives of Metallurgy and Materials

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2015

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tom Vol. 60, iss. 3

2131-2137

EN

The stability of austenite is one of the most dominant factors affecting the toughness properties of high Co-Ni steels such as Aermet 100 and AF1410. Thus, the aim of this work was to get a deeper understanding on the impact of combined heat and cryogenic treatment on the stability of retained and reverted austenite. In order to characterize the evolution of the phase fraction of austenite during tempering at different temperatures and times, X-ray diffraction analyses were carried out. The stability of austenite, which was formed during tempering, was analyzed with dilatometric investigations by studying the transformation behavior of the austenite during cooling from tempering temperature down to −100°C. Additionally, transmission electron microscopy investigations were performed to characterize the chemical composition and phase distribution of austenite and martensite before and after tempering.

PL

Stabilność austenitu jest jednym z najbardziej dominujących czynników mających wpływ na ciągliwość stali Co-Ni, takiej jak Aermet 100 i AF1410. Celem pracy było głębsze zrozumienia wpływu skojarzonego nagrzewania i obróbki kriogenicznej na stabilność austenitu szczątkowego i przemienionego. Ewolucję udziału fazy austenitycznej podczas odpuszczania w różnych temperaturach i czasach przeprowadzono stosując rentgenowskie badania dyfrakcyjne. Stabilność austenitu, który powstał podczas odpuszczania, badano metodą dylatometryczną, analizując zachowanie się austenitu podczas odpuszczania w temperaturach poniżej –100°C. Zrealizowano badania metodą mikroskopii elektronowej w celu określenia składu chemicznego i rozkładu austenitu i martenzytu przed i po odpuszczaniu.

3

Effects Of The Combined Heat And Cryogenic Treatment On The Stability Of Austenite In A High Co-Ni Steel

38%

Gruber M. , Ebner R. , Ploberger S. , Ressel G. , Wiessner M. , Hausbauer M. , Marsoner S.

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4

Assessment of salt tolerance of Nasturtium officinale R. Br. using physiological and biochemical parameters

32%

Kaddour R. , Draoui E. , Baatour O. , Mahmoudi H. , Tarchoun I. , Nasri N. , Gruber M. , Lachaal M.

Acta Physiologiae Plantarum

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2013

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tom 35

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nr 12

EN

Nasturtium officinale R. Br. seedlings were treated with a range of NaCl concentrations (0, 50, 100 and 150 mM) for 21 days after seedling emergence. Physiological analysis based on growth and mineral nutrition, showed a substantial decrease in leaf dry matter with 150 mM NaCl treatment. The growth decrease was correlated with nutritional imbalance and a reduction in potassium accumulation and transport to the leaves. At the same time, we noted an increase in leaf sodium and chloride accumulation and transport. Salt tolerance of N. officinale under 100 mM NaCl was associated with osmotic adjustment via Na+ and Cl− and the maintenance of high K+/Na+ selectivity. Salt decreased carotenoid content more than chlorophylls and also disturbed membrane integrity by increasing malondialdehyde content and electrolyte leakage. At 150 mM NaCl, an increase in antioxidant enzyme-specific activities for superoxide dismutase, catalase and guaiacol peroxidase occurred in concert with a decrease in ascorbic acid, polyphenol, tannin and flavonoid content. These results indicate that N. officinale can maintain growth and natural antioxidant defense compounds such as, vitamin C, carotenoids, and polyphenols, when cultivated in 100 mM NaCl, but not at higher salt levels.

5

Physiological and molecular responses of two Arabidopsis accessions to calcium amendment and salt constraint

32%

Kaddour R. , Mahmoudi H. , Baatour O. , Tarchoun I. , Nasri N. , ben Saleh I. , Berthomieu P. , Gruber M. , Lachaal M.

Acta Physiologiae Plantarum

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2012

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tom 34

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nr 2

EN

The Arabidopsis thaliana NOK2 accession displays salt tolerance compared to more commonly known A. thaliana accessions, such as Col-0, but the basis of this phenotypic feature is unknown. This work was focused on determining whether salt tolerance in NOK2 plants is affected by calcium supplementation to the growth medium. A. thaliana seedlings were grown in pots containing a mixture of sand and peat under controlled conditions in a low-level Ca(NO₃)₂ medium supplemented with 0 or 50 mM NaCl with and without amendment with two higher levels of Ca(NO₃)₂. Calcium amendment was beneficial for salt-treated NOK2 plants, as shown by the increase in dry weight of NOK2 plants with and without NaCl, but had no impact on Col-0 biomass. Sodium accumulation decreased as a function of calcium amendment in NOK2, while Col-0 maintained its high Na levels under these conditions. Leaf K⁺ content, K⁺ uptake, and Ca content decreased in NOK2 and Col-0 plants growing in the low-level Ca medium when NaCl was added, but rose in leaves of both accessions with calcium amendment, although K remained low in both accessions in the absence of NaCl. K⁺/Na⁺ selectivity increased preferentially in NOK2 with increasing calcium in the presence of NaCl, but when Na was restricted and not under any conditions in Col-0. Preferential effects of calcium were not observed on the transcript accumulation of seven Na⁺, K⁺ or Ca²⁺ transport genes for either of the accessions, except for increased transcription of the CAX4 gene in NOK2 leaves at the highest calcium concentration used (5 mM). Leaf membrane leakage, which increased two-fold higher in Col-0 under salt application compared with the increase in NOK2, declined for both accessions in response to calcium supplementation, and in NOK2 this decline reached no salt levels when Ca²⁺ amendments were highest. Chlorophyll and carotenoid content dropped two-fold in Col-0 in response to salt, but were unchanged in NOK2 under these conditions. In contrast, leaf anthocyanins, which were normally tenfold higher in Col-0 than in NOK2 in the lowlevel Ca²⁺ medium, declined in Col-0 plants as a function of Ca²⁺ supplementation, but were maintained at low levels in NOK2 leaves regardless of salinity and calcium. In conclusion, NOK2 plants responded positively to calcium supplementation by improving biomass yield during salinity treatment, whereas this amendment only affected Col-0 by reducing its permeability and anthocyanin titre. K⁺/Na⁺ selectivity appeared to be an important characteristic of NOK2 response to calcium. The regulation of this response may involve the CAX4 Ca²⁺/H⁺ vacuolar transport gene, but does not appear to involve six other common ion transporters.