Low-Frequency Spectrum Asymptotics as a Measure of Nonstationarity of Some Geophysical Processes

2013 ◽  
pp. 97-105
Author(s):  
V. B. Lysenko ◽  
V. F. Pisarenko
Keyword(s):  
Frequency Spectrum ◽  
Low Frequency ◽  
Geophysical Processes

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

LXXV. The low frequency spectrum of the cygnus (19N4A) and cassiopeia (23N5A) radio sources

1956 ◽  
Vol 1 (8) ◽  
pp. 725-737 ◽  
Author(s):  
R. J. Lamden ◽  
A. C. B. Lovell
Keyword(s):  
Frequency Spectrum ◽  
Low Frequency ◽  
Radio Sources

scholarly journals Strength in numbers in the low-frequency spectrum

2015 ◽  
Vol 16 (11) ◽  
pp. 623-623
Author(s):  
Magdalena Skipper
Keyword(s):  
Frequency Spectrum ◽  
Low Frequency

scholarly journals Frontispiz: Observation of the Low‐Frequency Spectrum of the Water Trimer as a Sensitive Test of the Water‐Trimer Potential and the Dipole‐Moment Surface

2020 ◽  
Vol 132 (28) ◽  
Author(s):  
Raffael Schwan ◽  
Chen Qu ◽  
Devendra Mani ◽  
Nitish Pal ◽  
Gerhard Schwaab ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Frequency Spectrum ◽  
Low Frequency ◽  
Sensitive Test ◽  
Water Trimer

Origin of low-frequency spectrum structure of four-photon scattering in liquid water

1998 ◽  
Vol 66 (1) ◽  
pp. 91-94 ◽  
Author(s):  
A.F. Bunkin ◽  
G.A. Lyakhov ◽  
A.A. Nurmatov ◽  
N.V. Suyazov
Keyword(s):  
Frequency Spectrum ◽  
Liquid Water ◽  
Low Frequency ◽  
Photon Scattering ◽  
Spectrum Structure

A New Advanced Topology of Stacked Multicell Inverter

2014 ◽  
Vol 15 (4) ◽  
pp. 327-333 ◽  
Author(s):  
Mohamad R. Banaei ◽  
M. R. Jannati Oskuee ◽  
F. Mohajel Kazemi
Keyword(s):  
Frequency Spectrum ◽  
Output Voltage ◽  
Low Frequency ◽  
Experimental Results ◽  
The Novel ◽  
Stored Energy ◽  
Well Performance ◽  
Flying Capacitors ◽  
Voltage Frequency ◽  
Simulation Results

Abstract In this paper, a new advanced topology of stacked multicell inverter is proposed which is generally suitable for high number of steps associated with a low number of switches. Compared with traditional flying capacitor multicell and stacked multicell (SM) inverters, doubling the number of output voltage levels and the RMS value, ameliorating the output voltage frequency spectrum, decreasing the number and rating of components, stored energy and rating of flying capacitors are available with the proposed inverter. These improvements are achieved by adding only four low-frequency switches to the traditional SM inverter’s structure. The suggested topology is simulated using MATLAB/SIMULINK software, and simulation results are presented to indicate well-performance of the novel converter. In addition, the experimental results of proposed topology prototype have been presented to validate its practicability.

Aerodynamic Numerical Investigation of Low-Pressure Steam Turbine Last Stage Under Low Load Conditions With Mode Decomposition Methods

2019 ◽  
Author(s):  
Ping Hu ◽  
Tong Lin ◽  
Rui Yang ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Steam Turbine ◽  
Frequency Spectrum ◽  
Low Frequency ◽  
Low Pressure ◽  
Unsteady Pressure ◽  
Mode Decomposition ◽  
Low Load ◽  
Last Stage ◽  
Operating Points ◽  
Load Conditions

Abstract It is common that steam turbine works at different operating points, especially under low load conditions, to cater to complex and varied demands for power generation recently. Considering the long and thin shape of last stage moving blades (LSMBs) in a low-pressure (LP) steam turbine, there are many challenges to design a suitable case which balances global efficiency against sufficient structure strength when suffering excitations at low load operating points. In present work, the aim is to extract specific aerodynamic excitations and recognize their distribution and propagation features. Firstly, steady 3D computational fluid dynamics (CFD) calculations are simulated at 25GV and 17GV (25% and 17% of design mass flow conditions) and corresponding unsteady calculations are performed with enough rotor revolutions to obtain integrated flow periodicities. Unsteady pressure signals near tip region of LSMBs are monitored circumferentially in both static and rotating coordinates. The fast Fourier transformation (FFT) results of unsteady pressure signals show that there are broadband humps with small disturbance amplitudes in low frequency spectrum at 25GV, however, a sharp spike is shown in low frequency spectrum at 17GV. Further, circumferential mode decomposition (CMD) method has been applied to distinguish different fluctuations in frequency and the mode numbers and circumferential propagating pace of which have been obtained. Finally, dynamic mode decomposition (DMD) method has been performed to describe detailed mode shapes of featured flow perturbances both in static and rotating coordinate system. These analyses indicate that at 25GV, a band of unsteady responses with very low amplitude was noted which has some features similar to rotating instability (RI). However, distribution and propagation features of flow unsteadiness at 17GV are in good agreement with rotating stall (RS) in compressor.

An interpretation of the low-frequency spectrum of liquid water

2003 ◽  
Vol 118 (1) ◽  
pp. 452-453 ◽  
Author(s):  
Joan Àngel Padró ◽  
Jordi Martı́
Keyword(s):  
Frequency Spectrum ◽  
Liquid Water ◽  
Low Frequency
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