Observation of a local maximum in the stationary turbulent spectrum of capillary waves on the surface of liquid hydrogen
The results of experimental studies of wave turbulence in a system of capillary waves formed on the surface of liquid hydrogen at a tempera-ture of 15 K in a cylindrical cell with monochromatic radially symmetric pumping are presented. The local maximum formation with adecrease in the pumping amplitude was observed for thefirst time in the high-frequency region of the inertial range of the stationary turbu-lent spectrum at the direct cascade edge. The occurrence of a local maximum can be associated with a significant manifestation of viscousdamping in the high-frequency region of the spectrum.
Experiments on the decay instability of gravity-capillary waves excited by alternating electric fields with frequencies of 14-30 Hz on a charged liquid hydrogen surface in a rectangular cell are reported. An exponential increase in the amplitudes of the subharmonics caused by decay of the wave at the pump frequency is found. For the first time, the experimentally observed growth rate of the decay instability and damping coefficient for the surface waves in the rectangular cell yield an estimate of the coefficient for three-wave interactions of gravity-capillary waves in liquid hydrogen.
Formation of low frequency harmonics on turbulent distribution in the system of waves on the surface of liquid hydrogen has been studied in the frequency range 1-100 Hz (capillary-gravity waves). It is shown that the geometry of the experimental cell has a significant influence on the direct cascade of capillary waves generated by monochromatic force as well as on the direction of the wave energy transfer from the range of pumping towards that of dissipation. Besides a direct turbulent cascade, single half-frequency harmonic generation was observed in a cylindrical cell under high pump power. In a square cell we observed not only a half-frequency harmonic but a number of low frequency harmonics below the driving frequency generated by the nonlinear three-wave interaction. In the case of a rectangular cell we observed formation of incommensurate low frequency harmonics caused by the three-wave interaction of capillary waves and generation of a wave mode of similar to 1Hz in the frequency range of gravity waves which could be attributed to the four-wave interaction.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.