Российский фонд
фундаментальных
исследований

Физический факультет
МГУ им. М.В.Ломоносова
 

P

Panja S.Ch.

 

Soumya Roy, Prasad A., Panja S.Ch., Ghosh K., Patra S.N. «A search for periodicities in F10.7 solar radio flux data» Астрономический вестник. Исследования Солнечной системы, 53, № 3, с. 240 (2019)

The radio frequency emission at 10.7 cm (or 2800 MHz) wavelength (considered as solar flux density) out of different possible wavelengths is usually selected to identify periodicities because of its high correlation with solar extreme ultraviolet radiation as well as its complete and long observational record other than sunspot related indices. The solar radio flux at 10.7 cm wavelength plays a very valuable role for forecasting the space weather because it is originated from lower corona and chromospheres region of the Sun. Also, solar radio flux is a magnificent indicator of major solar activity. Here in the present work the solar radio flux data from 1965 to 2014 observed at the Domimion Radio Astrophysical Observatory in Penticton, British Columbia has been processed using Date Compensated Discrete Fourier Transform (DCDFT) to identify predominant periods within the data along with their confidence levels. Also, the multi-taper method (MTM) for periodicity analysis is used to validate the observed periods. Present investigation exhibits multi-periodicity of the time series F10.7 solar radio flux data around 27, 57, 78, 127, 157, 4096 days etc. The observed periods are also compared with the periods of MgII Index data using same algorithm as MgII Index data has 99.9% correlation with F10.7 Solar Radio Flux data. It can be observed that the MgII index data exhibits similar periodicities with very high confidence levels. Present investigation also clearly indicates that the computed results are very much confining with the results obtained in different communications for the similar data of 10.7 cm Solar Radio Flux as well as for the other solar activities.

Астрономический вестник. Исследования Солнечной системы, 53, № 3, с. 240 (2019) | Рубрика: 18

Patra S.N.

 

Soumya Roy, Prasad A., Panja S.Ch., Ghosh K., Patra S.N. «A search for periodicities in F10.7 solar radio flux data» Астрономический вестник. Исследования Солнечной системы, 53, № 3, с. 240 (2019)

The radio frequency emission at 10.7 cm (or 2800 MHz) wavelength (considered as solar flux density) out of different possible wavelengths is usually selected to identify periodicities because of its high correlation with solar extreme ultraviolet radiation as well as its complete and long observational record other than sunspot related indices. The solar radio flux at 10.7 cm wavelength plays a very valuable role for forecasting the space weather because it is originated from lower corona and chromospheres region of the Sun. Also, solar radio flux is a magnificent indicator of major solar activity. Here in the present work the solar radio flux data from 1965 to 2014 observed at the Domimion Radio Astrophysical Observatory in Penticton, British Columbia has been processed using Date Compensated Discrete Fourier Transform (DCDFT) to identify predominant periods within the data along with their confidence levels. Also, the multi-taper method (MTM) for periodicity analysis is used to validate the observed periods. Present investigation exhibits multi-periodicity of the time series F10.7 solar radio flux data around 27, 57, 78, 127, 157, 4096 days etc. The observed periods are also compared with the periods of MgII Index data using same algorithm as MgII Index data has 99.9% correlation with F10.7 Solar Radio Flux data. It can be observed that the MgII index data exhibits similar periodicities with very high confidence levels. Present investigation also clearly indicates that the computed results are very much confining with the results obtained in different communications for the similar data of 10.7 cm Solar Radio Flux as well as for the other solar activities.

Астрономический вестник. Исследования Солнечной системы, 53, № 3, с. 240 (2019) | Рубрика: 18

Peng Zilong

 

Zhou Fulin, Wang Bin, Fan Jun, Peng Zilong «Theoretical and Numerical Studies on in vacuo Structural Admittance of an Infinite, Coated Cylindrical Shell» Акустический журнал, 65, № 1, с. pp. 14-22 (2019)

Studying the interaction of sound with a coated cylindrical shell immersed in water is essential for improving existing underwater target detection and classification algorithms. According to the impedance theory of sound scattering, in vacuo structural admittance describes the relationship between the sonar-induced forces and the resulting vibration on the surface, which can be used to solve the problem of the acoustic scattering and radiation. In this work, we investigate numerically and theoretically the structural admittance of a coated cylindrical shell. Analytical expressions of the structural admittance are derived for different external forces: a plane acoustic wave, a normal point force, and a random noise field. The structural admittance is also numerically evaluated. The results show that the structural admittance is independent of exterior medium and fluid loading. According to the impedance theory of sound scattering, the scattered field of a coated cylindrical shell is calculated by combining the structural-, acoustic-, and internal-admittance matrices. Because of the non-local property of structural surface admittance, we build an algebraic model of a coated object by nonlinear curve fitting and study a local approximation of the structural admittance. We also find that simplifying the large matrices is useful for research on structural vibrations. Thus, this work presents a systematic study of the acoustic scattering characteristics of structural admittance of an infinite, coated cylindrical shell.

Акустический журнал, 65, № 1, с. pp. 14-22 (2019) | Рубрика: 07.11

Peris-Fajarnés G.

 

Dunai L., Lengua I., Iglesias M., Peris-Fajarnés G. «Buffeting-Noise Evaluation in Passenger Vehicle BMV 530d» Акустический журнал, 65, № 5, с. pp. 578-582 (2019)

In this paper we exhibit the results and evaluation of the buffeting-noise effect in a BMW 530d model vehicle. The buffeting noise was studied in real measurement conditions in an outdoors highway at different speeds. We evaluate different listening positions inside the vehicle to demonstrate that the buffeting-noise effect is independent from the listener position.

Акустический журнал, 65, № 5, с. pp. 578-582 (2019) | Рубрика: 10.06

Petrov P.S.

 

Tang Jun , Petrov P.S., Piao Shengchun , Kozitskiy S.B. «On the Method of Source Images for the Wedge Problem Solution in Ocean Acoustics: Some Corrections and Appendices» Акустический журнал, 64, № 2, с. pp. 225-236 (2018)

In this study the method of source images for the problem of sound propagation in a penetrable wedge [G. Deane and M. Buckingham, J. Acoust. Soc. Am. 93 (1993) 1319-1328] is revisited. This solution is very important three-dimensional (3D) benchmark in computational underwater acoustics, since a wedge bounded from above by the sea surface and overlying a sloping penetrable bottom is the simplest model of a shallow-sea waveguide near the coastline. The corrected formulae for the positions of the source images and bottom images are presented together with the explanation of their derivation. The problem of branch choice in the reflection coefficient is thoroughly discussed, and the corresponding explicit formulae are given. In addition, numerical validation of the proposed branch choice schemes and the resulting wedge problem solutions are presented. Finally, source images solution is computed for a series of examples with different ratios of shear and bulk moduli in the bottom. The interplay between the acoustic-elastic waves coupling and the horizontal refraction in the wedge is demonstrated.

Акустический журнал, 64, № 2, с. pp. 225-236 (2018) | Рубрика: 07.02

Piao Shengchun

 

Tang Jun , Petrov P.S., Piao Shengchun , Kozitskiy S.B. «On the Method of Source Images for the Wedge Problem Solution in Ocean Acoustics: Some Corrections and Appendices» Акустический журнал, 64, № 2, с. pp. 225-236 (2018)

In this study the method of source images for the problem of sound propagation in a penetrable wedge [G. Deane and M. Buckingham, J. Acoust. Soc. Am. 93 (1993) 1319-1328] is revisited. This solution is very important three-dimensional (3D) benchmark in computational underwater acoustics, since a wedge bounded from above by the sea surface and overlying a sloping penetrable bottom is the simplest model of a shallow-sea waveguide near the coastline. The corrected formulae for the positions of the source images and bottom images are presented together with the explanation of their derivation. The problem of branch choice in the reflection coefficient is thoroughly discussed, and the corresponding explicit formulae are given. In addition, numerical validation of the proposed branch choice schemes and the resulting wedge problem solutions are presented. Finally, source images solution is computed for a series of examples with different ratios of shear and bulk moduli in the bottom. The interplay between the acoustic-elastic waves coupling and the horizontal refraction in the wedge is demonstrated.

Акустический журнал, 64, № 2, с. pp. 225-236 (2018) | Рубрика: 07.02

Prasad A.

 

Soumya Roy, Prasad A., Panja S.Ch., Ghosh K., Patra S.N. «A search for periodicities in F10.7 solar radio flux data» Астрономический вестник. Исследования Солнечной системы, 53, № 3, с. 240 (2019)

The radio frequency emission at 10.7 cm (or 2800 MHz) wavelength (considered as solar flux density) out of different possible wavelengths is usually selected to identify periodicities because of its high correlation with solar extreme ultraviolet radiation as well as its complete and long observational record other than sunspot related indices. The solar radio flux at 10.7 cm wavelength plays a very valuable role for forecasting the space weather because it is originated from lower corona and chromospheres region of the Sun. Also, solar radio flux is a magnificent indicator of major solar activity. Here in the present work the solar radio flux data from 1965 to 2014 observed at the Domimion Radio Astrophysical Observatory in Penticton, British Columbia has been processed using Date Compensated Discrete Fourier Transform (DCDFT) to identify predominant periods within the data along with their confidence levels. Also, the multi-taper method (MTM) for periodicity analysis is used to validate the observed periods. Present investigation exhibits multi-periodicity of the time series F10.7 solar radio flux data around 27, 57, 78, 127, 157, 4096 days etc. The observed periods are also compared with the periods of MgII Index data using same algorithm as MgII Index data has 99.9% correlation with F10.7 Solar Radio Flux data. It can be observed that the MgII index data exhibits similar periodicities with very high confidence levels. Present investigation also clearly indicates that the computed results are very much confining with the results obtained in different communications for the similar data of 10.7 cm Solar Radio Flux as well as for the other solar activities.

Астрономический вестник. Исследования Солнечной системы, 53, № 3, с. 240 (2019) | Рубрика: 18