Diffusion Processes Influenced by Conjugate-Point Wave Phenomena

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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Ergodic Control of Diffusion Processes

10.1017/cbo9781139003605 ◽

2009 ◽

Cited By ~ 13

Author(s):

Ari Arapostathis ◽

Vivek S. Borkar ◽

Mrinal K. Ghosh

Keyword(s):

Diffusion Processes ◽

Ergodic Control

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THE STATIONARY DISTRIBUTIONS AND THE STEADY PROBABILITY CURRENTS OF ONE-DIMENSIONAL DIFFUSION PROCESSES UNDER NON-LOCAL BOUNDARY CONDITIONS

Acta Mathematica Scientia ◽

10.1016/s0252-9602(18)30713-6 ◽

1981 ◽

Vol 1 (2) ◽

pp. 195-206

Author(s):

Chengxun Wu ◽

Maozheng Guo

Keyword(s):

Boundary Conditions ◽

Diffusion Processes ◽

Stationary Distributions ◽

One Dimensional ◽

Local Boundary ◽

Dimensional Diffusion ◽

Non Local

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Fundamentals of Wave Phenomena

10.1049/sbew044e ◽

2010 ◽

Cited By ~ 3

Author(s):

Akira Hirose ◽

Karl E. Lonngren

Keyword(s):

Wave Phenomena

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NMR-Study of Structure and Diffusion Processes in Li3N

Le Journal de Physique Colloques ◽

10.1051/jphyscol:1980607 ◽

1980 ◽

Vol 41 (C6) ◽

pp. C6-28-C6-31 ◽

Cited By ~ 2

Author(s):

R. Messer ◽

H. Birli ◽

K. Differt

Keyword(s):

Diffusion Processes ◽

Nmr Study ◽

And Diffusion

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Simulation of vibration piercing of pipe blank at press

Ferrous Metallurgy Bulletin of Scientific Technical and Economic Information ◽

10.32339/0135-5910-2020-11-1128-1138 ◽

2020 ◽

Vol 76 (11) ◽

pp. 1128-1138

Author(s):

S. R. Rakhmanov

Keyword(s):

High Frequency ◽

Deformation Zone ◽

Pipe Blank ◽

Equipment Operation ◽

Metal Deformation ◽

Technological Tool ◽

High Frequency Vibrations ◽

Pipe Blanks ◽

Wave Phenomena

In some cases, the processes of piercing or expanding pipe blanks involve the use of high-frequency active vibrations. However, due to insufficient knowledge, these processes are not widely used in the practice of seamless pipes production. In particular, the problems of increasing the efficiency of the processes of piercing or expanding a pipe blank at a piercing press using high-frequency vibrations are being solved without proper research and, as a rule, by experiments. The elaboration of modern technological processes for the production of seamless pipes using high-frequency vibrations is directly related to the choice of rational modes of metal deformation and the prediction resistance indicators of technological tools and the reliability of equipment operation. The creation of a mathematical model of the process of vibrating piercing (expansion) of an axisymmetric pipe blank at a piercing press of a pipe press facility is an actual task. A calculation scheme for the process of piercing a pipe plank has been elaborated. A dependence was obtained characterizing the speed of front of plastic deformation propagation on the speed of penetration of a vibrated axisymmetric mandrel into the pipe workpiece being pierced. The dynamic characteristics of the occurrence of wave phenomena in the metal being pierced under the influence of a vibrated tool have been determined, which significantly complements the previously known ideas about the stress-strain state of the metal in the deformation zone. The deformation fields in the zones of the disturbed region of the deformation zone were established, taking into account the high-frequency vibrations of the technological tool. It has been established that the choice of rational parameters (amplitude-frequency characteristics) of the vibration piercing process of a pipe blank results in significant increase in the efficiency of the process, the durability of the technological tool and the quality of the pierced blanks.

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