General Theorems on the Equivalence of Group Velocity and Energy Transport

1957 ◽  
Vol 105 (4) ◽  
pp. 1129-1137 ◽  
Author(s):  
M. A. Biot
Keyword(s):  
Group Velocity ◽  
Energy Transport

scholarly journals Acoustic Bloch wave energy transport and group velocity

1991 ◽  
Vol 89 (4B) ◽  
pp. 1971-1971
Author(s):  
Charles E. Bradley ◽  
David T. Blackstock
Keyword(s):  
Group Velocity ◽  
Wave Energy ◽  
Energy Transport ◽  
Bloch Wave

Energy, transport, and consumption in the Industrial Revolution

2019 ◽  
Vol 42 ◽  
Author(s):  
Joseph A. Tainter ◽  
Temis G. Taylor
Keyword(s):  
Mass Production ◽  
Industrial Revolution ◽  
Energy Transport ◽  
Underlying Assumption

Abstract We question Baumard's underlying assumption that humans have a propensity to innovate. Affordable transportation and energy underpinned the Industrial Revolution, making mass production/consumption possible. Although we cannot accept Baumard's thesis on the Industrial Revolution, it may help explain why complexity and innovation increase rapidly in the context of abundant energy.

Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions

1990 ◽  
Vol 48 (2) ◽  
pp. 110-111 ◽  
Author(s):  
F. Hasselbach ◽  
A. Schäfer
Keyword(s):  
Group Velocity ◽  
Wave Packets ◽  
Index Of Refraction ◽  
Electron Wave ◽  
Fringe Contrast ◽  
Faraday Cage ◽  
Optical Index ◽  
Wien Filter ◽  
Coherent Wave ◽  
Electric And Magnetic Fields

Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.

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