scholarly journals Experimental Studies of Plasma Confined in a Toroidal Heliac

1989 ◽  
Vol 42 (1) ◽  
pp. 73 ◽  
Author(s):  
BD Blackwell ◽  
SM Hamberger ◽  
LE Sharp ◽  
X-H Shi
Keyword(s):  
Magnetic Flux ◽  
High Frequency ◽  
Experimental Studies ◽  
Local Measurements ◽  
Gas Breakdown ◽  
Fluctuation Mode ◽  
Design Construction

The design, construction and operation of the prototype heliac SHEILA are described. Gas breakdown conditions are compared with high frequency discharges. Plasma isobars obtained from local measurements are shown to agree closely with computed magnetic flux surfaces for a range of magnetic configurations. The effect of changing the configuration on fluctuation mode numbers is demonstrated and shown to be consistent with the calculated rotational transforms.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

Information-Measuring Complex for Registration High Frequency Gravitational Waves

2020 ◽  
pp. 42-51
Author(s):  
I. S. Golyak ◽  
A. N. Morozov ◽  
A. L. Nazolin ◽  
S. E. Tabalin
Keyword(s):  
Solid State ◽  
Active Region ◽  
Gravitational Waves ◽  
Spectral Range ◽  
High Frequency ◽  
Experimental Studies ◽  
Yag Laser ◽  
Information Measuring ◽  
Measuring Complex ◽  
Fabry Perot

The information-measuring complex designed to register high-frequency fluctuations of the space-time metric and its main elements are described in paper. The complex is based on a Fabry-Perot interferometer with highly reflective mirrors and a two-meter resonator. A solid-state Nd: YAG laser with a wavelength λ = 1064 nm is used for pumping. To read the signal, an InGaAs receiver DET10N2, with a working spectral range of 500-1700 nm and an active region of 0.8 mm2, is applied. Using the developed complex, experimental studies of signal registration at readout frequencies of 1 MHz and 20 MHz were carried out. The graphs of signal fluctuations in time and the spectra constructed from them are given.

scholarly journals Acoustic Signatures of the Phases and Phase Transitions in the Blume Capel Model with Random Crystal Field

2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
Gul Gulpinar
Keyword(s):  
High Frequency ◽  
Sound Propagation ◽  
Ultrasonic Attenuation ◽  
Experimental Studies ◽  
Power Laws ◽  
Sound Attenuation ◽  
Irreversible Processes ◽  
Acoustic Signatures ◽  
Sound Dispersion ◽  
Good Agreement

Sound propagation in the Blume Capel model with quenched diluted single-ion anisotropy is investigated. The sound dispersion relation and an expression for the ultrasonic attenuation are derived with the aid of the method of thermodynamics of irreversible processes. A frequency-dependent dispersion minimum that is shifted to lower temperatures with rising frequency is observed in the ordered region. The thermal and sound frequency (ω) dependencies of the sound attenuation and effect of the Onsager rate coefficient are studied in low- and high-frequency regimes. The results showed that ωτ≪1 and ωτ≫1 are the conditions that describe low- and high-frequency regimes, where τ is the single relaxation time diverging in the vicinity of the critical temperature. In addition, assuming a linear coupling of sound wave with the order parameter fluctuations in the system and ε as the temperature distance from the critical point, we found that the sound attenuation follows the power laws α(ω,ε)~ω2ε-1 and α(ω,ε)~ω0ε1 in the low- and high-frequency regions, while ε→0. Finally, a comparison of the findings of this study with previous theoretical and experimental studies is presented and it is shown that a good agreement is found with our results.

HIGH FREQUENCY AHARONOV–BOHM OSCILLATIONS IN CARBON NANOTUBES

2003 ◽  
Vol 17 (04) ◽  
pp. 159-165
Author(s):  
LINFENG YANG ◽  
JIE JIANG ◽  
JINMING DONG
Keyword(s):  
Carbon Nanotubes ◽  
Magnetic Flux ◽  
High Frequency ◽  
Quantum Interference ◽  
Weak Localization ◽  
Experimental Results ◽  
Single Wall Carbon Nanotubes ◽  
Multiple Cycle ◽  
Breaking Length ◽  
Aharonov Bohm

We give a multiple-cycle quantum interference model and obtain magnetoresistance (MR) expression in the framework of the weak localization. The MR expression based upon finite phase-breaking length Lφ can explain well several experimental results about distinct negative magnetoresistance of carbon nanotubes. The higher-order oscillation peaks with magnetic flux exist in the MR can also be explained by our model. And a new method to measure the phase-breaking length Lφ of the single-wall carbon nanotubes has been proposed.

Efficient and reliable surge prevention algorithm for centrifugal compressor

2020 ◽  
Vol 92 (1) ◽  
pp. 47-59
Author(s):  
Grzegorz Liśkiewicz
Keyword(s):  
Working Conditions ◽  
High Frequency ◽  
Experimental Studies ◽  
Phase Portraits ◽  
Centrifugal Blower ◽  
Local Flow ◽  
Content Type ◽  
Operating Range ◽  
Surge Margin ◽  
External Conditions

Purpose The paper aims to present an outline of the technology of the active anti-surge algorithm based on high-frequency pressure measurement. The presented system is fast, inexpensive and reliable and does not limit the machine-operating range. Many contemporary anti-surge systems are based on theoretical surge margin. This solution limits machine operating range by about 10-15 per cent in the region of the highest pressure ratios. It is also often sensitive to change in external conditions such as temperature or density, as the system reacts to limits calculated theoretically. Design/methodology/approach This paper presents results of pressure measurements obtained on the low-speed centrifugal blower DP1.12. The pressure signals were presented in the form of phase diagrams, and conclusions were drawn from their phase portraits to develop the surge indication parameter. Findings The presented safety system uses the signal to develop the so-called (rate of derivative fluctuation) RDF parameter. In nominal working conditions, this parameter keeps the value close to 1. When RDF reaches values over 3, the anti-surge procedure should be implemented. Experimental studies have shown that this algorithm assures enough time to incur actions suppressing unstable phenomena. Originality/value The system reacts to real machine working conditions and is hence reliable. The RDF algorithm could also be used to identify local flow instabilities, as well as off-design operation.

Experimental Studies on Attenuation of Rotor-Stator Dynamics: Effects of High-Frequency Inclusion and Annular Fluid

2018 ◽  
Author(s):  
Meryem Kanzari ◽  
Mohammed AlQaradawi ◽  
Balakumar Balachandran
Keyword(s):  
High Frequency ◽  
Complex Dynamics ◽  
Experimental Studies ◽  
Flexible Rotor ◽  
Flexible Rotors ◽  
Speed Modulation ◽  
Model Predictions ◽  
Drive Speed ◽  
The Stability ◽  
Three Degree Of Freedom

Flexible, rotating structures can experience complex dynamics, when torsional and lateral motions are involved. Oilwell drill strings form one example of such structures. In the present study, the authors investigate the influence of sinusoidal drive speed modulation on whirling motions of flexible rotors with contact interactions. For two types of drilling-like operations, one with drill mud and another without drill mud, the stability of motions is studied. A laboratory-scale drill rig is used to study the dynamics of a flexible rotor, which is driven at one end and housed within a stator at the other end. Experimental results are presented and discussed for different drive speeds. The findings suggest that the addition of drill mud in the annular space between the rotor and stator along with high-frequency modulation in the drive input helps attenuate lateral motions. The torsional motions appear to be influenced more by the high-frequency drive speed modulation. A three-degree-of-freedom model has been constructed to study lateraltorsional dynamics of a rotor-stator system. The model predictions are compared with the experimental data. The findings of this work have relevance for constructing practical solutions to control whirl dynamics of flexible rotors such as drill strings.

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