Spatially periodic structures in electron swarms and the Franck-Hertz experiment

2000 ◽  
Vol 33 (3) ◽  
pp. 507-520 ◽  
Author(s):  
R E Robson ◽  
B Li ◽  
R D White
Keyword(s):  
Periodic Structures ◽  
Spatially Periodic

Laser-Induced Spatially Periodic Structures on the Titanium Surface in n-Hexane at Different Pressures

2020 ◽  
Vol 46 (8) ◽  
pp. 779-782
Author(s):  
D. A. Kochuev ◽  
K. S. Khor’kov ◽  
A. S. Chernikov ◽  
R. V. Chkalov ◽  
V. G. Prokoshev
Keyword(s):  
Titanium Surface ◽  
Periodic Structures ◽  
Spatially Periodic

scholarly journals Nonlinear dynamics of radiation of high-current beams of charged particles in spatially periodic structures

2021 ◽  
pp. 62-72
Author(s):  
Svetlana N. Sytova
Keyword(s):  
Free Electron ◽  
High Efficiency ◽  
Periodic Structures ◽  
Wide Spectrum ◽  
Charged Particles ◽  
Travelling Wave ◽  
Free Electron Lasers ◽  
High Current ◽  
Spatially Periodic ◽  
Spectral Ranges

Provided a review of physical processes underlying the functioning of vacuum electronic devices, namely, nonlinear processes of radiation of  high-current beams of charged particles during their passage through spatially periodic structures (resonators) and their interaction with an electromagnetic field. Principles of functioning of travelling wave tubes, backward wave tubes, multi-wave Cherenkov generators, free electron lasers and free electron masers, volume free electron lasers are considered. These devices operate in a wide spectrum range from microwave to X-ray, have high efficiency, and allow obtaining high radiation powers in narrow spectral ranges. Increase the performance and reliability of electronic vacuum devices is based on improving the complex electromagnetic structures in resonators. The article demonstrates a variety of such devices with an obvious generality of physical principles used in them. Nonlinear chaotic dynamics of their functioning is considered. Particular attention is paid to consideration of principles of operation of volume free electron lasers as well as their difference from other devices.

scholarly journals Flow and Convection in Metal Foams: A Survey and New CFD Results

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 155
Author(s):  
Beatrice Pulvirenti ◽  
Michele Celli ◽  
Antonio Barletta
Keyword(s):  
Heat Transfer ◽  
Metal Foam ◽  
Periodic Structures ◽  
Metal Foams ◽  
Balance Model ◽  
Macroscopic Modeling ◽  
Flow And Heat Transfer ◽  
External Cooling ◽  
Spatially Periodic ◽  
Pros And Cons

Metal foams are widely studied as possible tools for the enhancement of heat transfer from hot bodies. The basic idea is that a metal foam tends to significantly increase the heat exchange area between the hot solid body and the external cooling fluid. For this reason, this class of porous materials is considered as a good candidate for an alternative to finned surfaces, with different pros and cons. Among the pros, we mention the generally wider area of contact per unit volume between solid and fluid. Among the cons is the difficulty to produce different specimens with the same inner structure, with the consequence that their performance may be significantly variable. This paper will offer a survey of the literature with a focus on the main heat transfer characteristics of the metal foams and the energy balance model based on Local Thermal Non-Equilibrium (LTNE). Then, a numerical simulation of the heat transfer at the pore-scale level for an artificial foam with a spatially periodic structure will be discussed. Finally, these numerical results will be employed to assess the macroscopic modeling of the flow and heat transfer in a metal foam. More precisely, the Darcy–Forchheimer model and the LTNE model adopted to describe the momentum and energy transfer in metal foams have been validated for metallic periodic structures.

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