scholarly journals Observation of coherent oscillation in single-passage Landau-Zener transitions

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Guozhu Sun ◽  
Xueda Wen ◽  
Ming Gong ◽  
Dan-Wei Zhang ◽  
Yang Yu ◽  
...  
Keyword(s):  
Coherent Oscillation ◽  
Single Passage

scholarly journals Single-passage readout of atomic quantum memory

2006 ◽  
Vol 73 (2) ◽  
Author(s):  
J. Fiurášek ◽  
J. Sherson ◽  
T. Opatrný ◽  
E. S. Polzik
Keyword(s):  
Quantum Memory ◽  
Single Passage

Mythological Scraps

1930 ◽  
Vol 24 (2) ◽  
pp. 107-108
Author(s):  
H. J. Rose
Keyword(s):  
Single Passage

The Gods and Typhon.—The story of how the gods took bestial shape to hide from the fury of Typhon is several times told in Hellenistic and Latin authors. There seems no room for doubt that it is an aetiological myth, intended to explain the cult of beasts in Egypt, and also, in one or two versions, the sacredness of fish in Syria. That in one form, that given by Antoninus Liberalis, it goes back to Nikandros (presumably the Ετεροιούμενα) is reasonably certain. The doubtful point, to my mind, is whether it can be traced much further, and, in particular, whether it was known to Pindar, as is commonly assumed. The authority for supposing that he knew and referred to it is a single passage of Porphyry, de abstinentia III. 16 (= Pindar, frag. 91, Bergk). It runs: Πίνδαρος δὲ ἐν προσοδίοις παντας τοὺς θεοὺς ἐποίησεν ὃτε ύπὸ Τυϕῶνος ἐδιώκοντα οủκ ἀνθρώποις όμοιωθέντας ἀλλὰ τοις ἂλοις (ἀλόγοις Wesseling) ζῴοις έρασθέντα δἐ Πασιϕάης Δία γενέσθαι μἐν ταῦρον νῦν δὲ ἀετὸν και κύκνον.

On the Development of a Synchronized Harmonic Balance Method for Multiple Frequencies and its Application to LPT Flows

2020 ◽  
Author(s):  
Javier Crespo ◽  
Jesús Contreras
Keyword(s):  
Boundary Conditions ◽  
Time Domain ◽  
Harmonic Balance ◽  
Fourier Transforms ◽  
Harmonic Balance Method ◽  
Single Passage ◽  
Computational Performance ◽  
Runge Phenomenon ◽  
Numerical Instabilities ◽  
The Impact

Abstract The aim of this paper is to describe the development and application of a multi-frequency harmonic balance solver for GPUs, particularly suitable for the simulation of periodic unsteadiness in nonlinear turbomachinery flows comprised of a few dominant frequencies, with an unsteady multistage coupling that bolsters the flow continuity across the rotor/stator interface. The formulation is addressed with the time-domain reinterpretation, where several non-equidistant time instants conveniently selected are solved simultaneously. The set of required frequencies in each row is driven into the governing equations with the help of almost-periodic Fourier transforms for time derivatives and time shifted boundary conditions. The spatial repetitiveness inside each row can be exploited to perform single-passage simulations and the relative circumferential positioning of the rotors or stators and the different blade or vane counts is tackled by means of adding fictitious frequencies referring to non-adjacent rows therefore taking into account clocking and indexing effects. Existing multistage row coupling techniques of harmonic methods rely on the use of non-reflecting boundary conditions, based on linearizations, or time interpolation, which may lead to Runge phenomenon with the resulting numerical instabilities and non-preserving flux exchange. Different sets of time instants might be selected in each row but the interpolation in space and time across their interfaces gives rise to robustness issues due to this phenomenon. The so-called synchronized approach, developed in this work, consist of having the same time instances among the whole ensemble of rows, ensuring that flux transfer at sliding planes is applied more robustly. The combination of a set of shared non-equidistant time instances plus the use of unequal frequencies (real and fictitious) may spoil the Fourier transforms conditioning but this can be dramatically improved with the help of oversampling and instants selection optimization. The resulting multistage coupling naturally addresses typical numerical issues such as flow that might reverse locally across the row interfaces by means of not using boundary conditions but a local flux conservation scheme in the sliding planes. Some examples will be given to illustrate the ability of this new approach to preserve accuracy and robustness while resolving them. A brief analysis of results for a fan stage and a LPT multi-row case is presented to demonstrate the correctness of the method, assessing the impact in the modeling accuracy of the present approach compared with a time-domain conventional analysis. Regarding the computational performance, the speedup compared to a full annulus time-domain unsteady simulation is a factor of order 30 combining the use of single-passage rows and time spectral accuracy.

Investigation of Working Line Variation Onto Forced Response Vibrations of a Compressor Blisk

2020 ◽  
Author(s):  
Seif ElMasry ◽  
Arnold Kühhorn ◽  
Felix Figaschewsky
Keyword(s):  
Resonance Condition ◽  
Element Model ◽  
Forced Response ◽  
Mode Shapes ◽  
Aerodynamic Forces ◽  
Aerodynamic Damping ◽  
Single Passage ◽  
Influence Coefficients ◽  
Stator Vane ◽  
Operational Range

Abstract This paper aims to study the effect of varying the working line of a compressor onto the forced response vibrations of the blades of an integrally bladed disk (blisk). The investigated rotor belongs to a transonic research compressor, where various probes are placed to measure flow data at all stations and analyze blade vibrations. A single-passage CFD model of all compressor blade-rows is used for steady computations. Using a finite element model, the natural frequencies and mode shapes of the blisk across the operational range of the compressor are predicted. Thus, resonance conditions can be identified from the Campbell diagram. The variation of the compressor working line is investigated at 90% of the maximum shaft speed, where the resonance condition of the 11th blade mode family and the engine order corresponding to the aerodynamic distortion from the upstream stator vane is predicted. Using a single-passage model, time-accurate simulations of the investigated rotor are executed at various operating points, which cover the operational range of the compressor between choke and stall conditions. Aerodynamic damping ratios are calculated using the aerodynamic influence coefficients method at each point, in order to predict the resulting vibration amplitudes of the blades. Relatively high amplitudes of the modal aerodynamic forces are observed at the low working line. A detailed post-processing analysis is performed, as the change of flow incidence contributes largely in the increase of modal aerodynamic forces on the blade. The aerodynamic damping ratios increase with higher working lines, where the rotor achieves relatively higher pressure ratios. However, the damping decreases rapidly close to stall conditions. The trend of the predicted vibration amplitudes is compared to strain gauge measurements from the rig, which are registered during multiple acceleration maneuvers performed over different working lines. A strong correlation between the predicted and measured trends of the forced response vibration is witnessed.

scholarly journals Insights into the Acquisition of Virulence of Avian Influenza Viruses during a Single Passage in Ferrets

Viruses ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 915
Author(s):  
Butler ◽  
Middleton ◽  
Haining ◽  
Layton ◽  
Rockman ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Respiratory Tract ◽  
Severe Disease ◽  
Influenza Viruses ◽  
Mammalian Host ◽  
Upper Respiratory Tract ◽  
Avian Influenza Viruses ◽  
Single Passage ◽  
H5n1 Isolate ◽  
High Pathogenicity

Circulating avian influenza viruses pose a significant threat, with human infections occurring infrequently but with potentially severe consequences. To examine the dynamics and locale of the adaptation process of avian influenza viruses when introduced to a mammalian host, we infected ferrets with H5N1 viruses. As expected, all ferrets infected with the human H5N1 isolate A/Vietnam/1203/2004 showed severe disease and virus replication outside the respiratory tract in multiple organs including the brain. In contrast infection of ferrets with the avian H5N1 virus A/Chicken/Laos/Xaythiani26/2006 showed a different collective pattern of infection; many ferrets developed and cleared a mild respiratory infection but a subset (25–50%), showed extended replication in the upper respiratory tract and developed infection in distal sites. Virus from these severely infected ferrets was commonly found in tissues that included liver and small intestine. In most instances the virus had acquired the common virulence substitution PB2 E627K but, in one case, a previously unidentified combination of two amino acid substitutions at PB2 S489P and NP V408I, which enhanced polymerase activity, was found. We noted that virus with high pathogenicity adaptations could be dominant in an extra-respiratory site without being equally represented in the nasal wash. Further ferret passage of these mutated viruses resulted in high pathogenicity in all ferrets. These findings illustrate the remarkable ability of avian influenza viruses that avoid clearance in the respiratory tract, to mutate towards a high pathogenicity phenotype during just a single passage in ferrets and also indicate a window of less than 5 days in which treatment may curtail systemic infection.

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