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Fundamentals
Published in Mike Tooley, Lloyd Dingle, Engineering Science, 2020
So far, with respect to force systems, we have been restricted to the turning effect of forces taken one at a time. A couple occurs when two equal forces acting in opposite directions have their lines of action parallel.
Fluid Flow
Published in C. Anandharamakrishnan, S. Padma Ishwarya, Essentials and Applications of Food Engineering, 2019
C. Anandharamakrishnan, S. Padma Ishwarya
where C is the couple on one of the plates (Barnes et al., 1989). Couple refers to a pair of parallel forces equal in magnitude, which acts in opposite directions on an object, but not through the same point so as to produce a rotating or turning effect (Figure 4.12).
Chapter 1 Biomechanics
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
A couple is a special type of moment, created by two forces of equal magnitude acting in opposite directions, but separated by a distance. The magnitude of the couple is independent of the position of the point about which moments are taken, and no net force acts in any direction. (Check this by taking moments about different points and resolving along two axes.) Sometimes a couple is described as a pure bending moment.
Photodissociation dynamics of CO-forming channel of methyl formate at 193 nm: a computational study
Published in Molecular Physics, 2022
Po-Yu Tsai, Federico Palazzetti
The polar angle distribution of angular momentum includes the following pairs of angular momentum vectors (see Figure S3): Orbiting angular momentum (OAM) vs. rotational angular momentum of CO (AM(CO)), OAM vs. rotational angular momentum of methanol (AM(MeOH)) and AM(CO) vs. AM(MeOH). All these polar angle distributions show a broad profile with a peak position at 130° ∼ 160°. The results imply that the three angular momentum vectors spread out in three-dimensional space, subject to the constraint of angular momentum conservation (the parent molecule is non-rotating in simulation, jparent = 0) and without preference of alignment between any couple of vectors. The results also indicate that the dissociation takes place in a non-planar arrangement. On the contrary, if the parent molecule possesses a planar geometry during the dissociation, the rotational angular momentum vectors of products and their orbiting motion tend to align perpendicularly with respect to the dissociation plane. One expects to observe a large population at polar angles 180° or 0°, similarly to the three-centre TS pathway of H2CO → H2 + CO [44–46].
Balance and constitutive equations in thermoelectroelastic solids
Published in Journal of Thermal Stresses, 2018
The first topic investigated in this article is the form of the balance equations as they follow from the description based on the Maxwell stress and that with models emerging from the analysis of dipoles subject to the electric field. The view that the action of the electric field on the body is described by the Maxwell tensor gives the same (correct) result, in connection with the balance of linear and angular momentum, about the body force and the body couple. Differences arise in the balance of energy. By means of the total stress tensor , we state the balance of energy in the form (Eq. 5), whereas the balance via the insertion of appropriate terms yields Eq. (6). Hence, irrespective of the occurrence of the power , in Eq. (5) the power is whereas, in Eq. (6) the power is
Four-wave mixing in a non-degenerate four-level diamond configuration in the hyperfine Paschen–Back regime
Published in Journal of Modern Optics, 2018
D. J. Whiting, Renju S. Mathew, J. Keaveney, C. S. Adams, I. G. Hughes
In a weak external magnetic field, the nuclear spin and the electron angular momentum couple to give the total angular momentum ; the latter and its projection onto the field axis, are good quantum numbers. Decoupling of and occurs for stronger fields, and these vectors precess independently about the magnetic field; their projections and are the good quantum numbers in this regime. An estimate for the decoupling field, , above which the hyperfine Paschen–Back regime is achieved is given by , where is the ground-state hyperfine coupling coefficient, and is theBohr magneton. For Rb, T. We utilize a 0.6 T magnetic field to enter the HPB regime and comprehensively characterize four-wave mixing in a diamond scheme in a thermal Rb vapour. Further, we show that in this regime the observed 4WM signals can be mapped to an isolated four-level system that can be easily modelled using only simple four-level optical Bloch equations.