scholarly journals Evanescent acoustic-gravity modes in the isothermal atmosphere: systematization and applications to the Earth and solar atmospheres

2019 ◽  
Vol 37 (3) ◽  
pp. 405-415 ◽  
Author(s):  
Oleg K. Cheremnykh ◽  
Alla K. Fedorenko ◽  
Evgen I. Kryuchkov ◽  
Yuriy A. Selivanov

Abstract. The objects of research in this work are evanescent wave modes in a gravitationally stratified atmosphere and their associated pseudo-modes. Whereas the former, according to the dispersion relation, rapidly decrease with distance from a certain surface, the latter, having the same dispersion law, differ from the first by the form of polarization and the nature of decrease from the surface. Within a linear hydrodynamic model, the propagation features of evanescent wave modes in an isothermal atmosphere are studied. Research is carried out for different assumptions about the properties of the disturbances. In this way, a new wave mode – anelastic evanescent wave mode – was discovered that satisfies the dispersion relation ω2=kxgγ-1. Also, the possibility of the existence of a pseudo-mode related to it is indicated. The case of two isothermal media differing in temperature at the interface is studied in detail. It is shown that a non-divergent pseudo-mode with a horizontal scale kx∼1/2H1 can be realized on the interface with dispersion ω2=kxg. Dispersion relation ω2=kxgγ-1 at the interface of two media is satisfied by the wave mode, which has different types of amplitude versus height dependencies at different horizontal scales kx. The applicability of the obtained results to clarify the properties of the f-mode observed on the Sun is analyzed.

2019 ◽  
Author(s):  
Oleg K. Cheremnykh ◽  
Alla K. Fedorenko ◽  
Evgen I. Kryuchkov ◽  
Yuriy A. Selivanov

Abstract. The objects of research in this work are evanescent wave modes in a gravitationally stratified atmosphere and their associated pseudo-modes. Whereas the former, according to the dispersion relation, rapidly decrease with distance from a certain surface, the latter, having the same dispersion law, differ from the first by the form of polarization and the character of its decreasing away from the surface. Within a linear hydrodynamic model, the propagation features of evanescent wave modes in an isothermal atmosphere are studied. Research carried out for different assumptions about the properties of the medium. On this way, a new wave mode – anelastic evanescent wave mode – was discovered. Also, the possibility of the existence of a pseudo-mode related to it is indicated. The case of two isothermal media differing in temperature at the interface is studied in detail. It is shown that a non-divergent pseudo-mode with the dispersion of solar f-mode type can be realized on the interface for the specified horizontal scale. The newly discovered dispersion relation, at the interface of two media, is satisfied by the wave mode, which has different types of amplitude versus height dependencies at different horizontal scales. The applicability of the obtained results to clarify the properties of f-mode observed on the Sun is analyzed.


2018 ◽  
Author(s):  
Shivika Narang ◽  
Praphul Chandra ◽  
Shweta Jain ◽  
Narahari Y

The blockchain concept forms the backbone of a new wave technology that promises to be deployed extensively in a wide variety of industrial and societal applications. In this article, we present the scientific foundations and technical strengths of this technology. Our emphasis is on blockchains that go beyond the original application to digital currencies such as bitcoin. We focus on the blockchain data structure and its characteristics; distributed consensus and mining; and different types of blockchain architectures. We conclude with a section on applications in industrial and societal settings, elaborating upon a few applications such as land registry ledger, tamper-proof academic transcripts, crowdfunding, and a supply chain B2B platform. We discuss what we believe are the important challenges in deploying the blockchain technology successfully in real-world settings.


Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 479
Author(s):  
Irina Sokolik

This Special Issue aims at addressing the recent developments towards improving our understanding of the diverse radiative impact of different types of aerosols and clouds [...]


A variant of the Stoneley-wave problem, namely slip waves between two homogeneous elastic half-spaces whose interface is incapable of supporting shear stresses, is studied. For two isotropic half-spaces there is either no or one slip-wave mode. In the case of anisotropic half-spaces, the possibility of a new slip-wave mode, called the second slip-wave mode, arises. The case of two identical anisotropic half-spaces of the same orientation is discussed in detail; criteria for the existence of a second slip-wave mode in terms of the nature of the transonic state are developed. It is concluded that for many anisotropic media a second slip-wave mode will exist within certain ranges of orientation of the slip-wave geometry. Numerical computations for iron (cubic symmetry) demonstrate that second slip-wave modes indeed exist in this material.


Crystals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 66
Author(s):  
Connor D. Pierce ◽  
Kathryn H. Matlack

Phononic crystals (PCs) have been widely reported to exhibit band gaps, which for non-dissipative systems are well defined from the dispersion relation as a frequency range in which no propagating (i.e., non-decaying) wave modes exist. However, the notion of a band gap is less clear in dissipative systems, as all wave modes exhibit attenuation. Various measures have been proposed to quantify the “evanescence” of frequency ranges and/or wave propagation directions, but these measures are not based on measurable physical quantities. Furthermore, in finite systems created by truncating a PC, wave propagation is strongly attenuated but not completely forbidden, and a quantitative measure that predicts wave transmission in a finite PC from the infinite dispersion relation is elusive. In this paper, we propose an “evanescence indicator” for PCs with 1D periodicity that relates the decay component of the Bloch wavevector to the transmitted wave amplitude through a finite PC. When plotted over a frequency range of interest, this indicator reveals frequency regions of strongly attenuated wave propagation, which are dubbed “fuzzy band gaps” due to the smooth (rather than abrupt) transition between evanescent and propagating wave characteristics. The indicator is capable of identifying polarized fuzzy band gaps, including fuzzy band gaps which exists with respect to “hybrid” polarizations which consist of multiple simultaneous polarizations. We validate the indicator using simulations and experiments of wave transmission through highly viscoelastic and finite phononic crystals.


1949 ◽  
Vol 39 (3) ◽  
pp. 205-218
Author(s):  
S. K. Chakrabarty

Summary The equation of motion of the seismometer and the galvanometer in an electromagnetic seismograph has been derived in the most general form taking into consideration all the forces acting on the system except that produced by hysteresis. A general solution has been derived assuming that the earth or the seismometer frame is subjected to a sustained simple harmonic motion, and expressions for both the transient and the steady term in the solution have been given. The results for the particular case when the seismograph satisfies the Galitzin conditions can easily be deduced from the results given in the present paper. The results can now be used to study the response characteristics of all electromagnetic seismographs, whether they satisfy the Galitzin conditions or not, and will thus give an accurate theoretical picture of the response also of seismographs used for the study of “local earthquakes” and “microseisms” which do not in general obey the Galitzin conditions. The results obtained can also be used to get analytically the response of the seismographs for different types of earth motion from the very beginning, and not only after the transient term has disappeared. The theory of the response to simple tests used to determine the dynamic magnification of any seismograph and also to determine and check regularly the instrumental constants of the seismographs has been worked out. The results obtained can also be used for ascertaining the proper values of the instrumental constants suitable for the various purposes for which the seismographs are to be used.


2014 ◽  
Vol 14 ◽  
pp. 87-147 ◽  
Author(s):  
Florentina Badalanova Geller

Cosmogonies and mythopoesis in the Balkans and beyondCompared and contrasted in this article are three different types of accounts dealing with the cosmogonic and eschatological themes employed in Slavonic and Balkan oral tradition, para-Biblical literature and modern poetry. The focus of analysis is the cluster of motifs attested in the creation narrative of the apocryphal Legend of the Sea of Tiberias. Two versions are examined: the South-Slavonic one discovered in 1845 by V. Grigorovich in the Monastery of Slepche, and the 18th century Russian account from MS № 21.11.3 (fols. 3a–5b) from the Archaeographic Department of the Library of the Academy of Sciences [Библиотека Академии наук, Рукописный отдел] in St. Petersburg, composed most probably by an Old Believer; this manuscript is published here for the first time. Folklore counterparts of the apocryphal Legend of the Sea of Tiberias are treated, with special emphasis on the oral narratives from the Bulgarian diaspora in Bessarabia (God and the Devil Create the World Amicably but then Fall Out). Finally, a poem of the 20th century Bulgarian intellectual Pencho Slaveykov [Пенчо Славейков] from his anthology “On the Island of the Blessed” is discussed; the poem, entitled How God willed the Earth to come to be and what did Satanail do after that? was designated by Slaveykov himself as “a legend of the Bogomils”, and blended within his lyrics are dualistic themes and motifs attested in vernacular Christianity, with the hallmark of Haeresis Bulgarica. Kosmogonie i mitopoetyki na Bałkanach i nie tylkoW artykule zostały porównane trzy typy narracji zawierających wątki kosmogoniczne i eschatologiczne, które funkcjonują w słowiańskiej i bałkańskiej tradycji ustnej, literaturze parabiblijnej oraz poezji doby modernizmu. Przedmiotem uwagi stała się grupa motywów poświadczonych w narracji o stworzeniu, znanej z Legendy o Morzu Tyberiadzkim. Analizom poddane zostały dwie wersje: południowosłowiańska, odkryta w 1845 roku przez W. Grigorowicza w Monastyrze w Slepče, oraz ruska – z XVIII wieku, znajdująca się w kodeksie MS № 21.11.3 (fols. 3a–5b), przechowywanym w Oddziale Rękopisów Biblioteki Akademii Nauk w Sankt Petersburgu – skomponowana najprawdopodobniej w środowisku staroobrzędowców (rękopis ten jest tu publikowany po raz pierwszy). Następnie przeprowadzona została analiza odpowiedników folklorystycznych apokryficznej Legendy o Morzu Tyberiadzkim, ze szczegól­nym uwzględnieniem narracji ustnych funkcjonujących w bułgarskiej diasporze w Besarabii (Bóg i Diabeł tworzą świat w przyjaźni ale potem stają się wrogami). Na końcu został poddany interpretacji poemat z XX wieku autorstwa bułgarskiego modernisty Penczo Sławejkowa [Пенчо Славейков] z antologii Na wyspie błogosławionych [На острова на блажените]; poemat ten, zatytułowany Jak Bóg zezwolił, aby powstała ziemia i co potem uczynił Satanael?, został nazwany przez samego autora „legendą Bogomiłów”, i skompilowany w jego tekstach z dualistycznymi motywami występującymi w chrześcijaństwie tego regionu, a rozpoznawa­nymi jako haeresis bulgarica.


Author(s):  
M.V. Chernyshev

Every crisis of the world capitalist economy prompts a new wave of interest in long economic cycles. In the second half of the 20 century, the emergence of new social movements and activity of «traditional» working class can be analyzed as important barometers of socio-economic development in transitional economies of European countries towards postindustrial society. In this article the author employs a theory of the dynamics of protest waves developed by Ruud Koopmans to analyse social processes in West Germany and Italy between 1966 and 1974. Special attention is given to study of different types of social protest movements: spontaneous, semi-military groups and those affiliated with political parties. A special emphasis is put on showing how the protest wave started with confrontational actions, subsequently entered a phase of moderate mass mobilization, and ended up with a twin process of institutionalization and radicalization.


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