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CHAPTER 6 Transmission Techniques: Wire and Cable
Published in Douglas Self, Audio Engineering Explained, 2012
Crimping is probably the most popular method of terminating BNC and F connectors on coax cable. Like the solder method, it can be used on solid or stranded conductors and provides a good mechanical and electrical connection. This method is the most popular because there is no need for soldering so installation time is reduced. It is very important to use the proper size connector for a tight fi t on the cable. Always use the proper tool. Never use pliers as they are not designed to place the pressure of the crimp evenly around the connector. Pliers will crush the cable and can degrade the electrical properties of the cable.
Wrist extensor muscle activity is less task-dependent than wrist flexor muscle activity while simultaneously performing moderate-to-high handgrip and wrist forces
Published in Ergonomics, 2021
Davis A. Forman, Garrick N. Forman, Michael W. R. Holmes
The changes in relative contributions of handgrip and wrist forces from one condition to the next mimic certain workplace tasks or tasks of daily living. As a simple example, turning a nut with a set of locking pliers requires different magnitudes of handgrip and wrist force at different points throughout the task. At the beginning, the hand must exert a relatively large amount of force to compress the handles of the pliers and successfully lock them in place. Once locked, the hand need only grip the pliers with enough force to ensure steady contact while forces/torques are transmitted through the hand by the wrist and forearm to turn the pliers. Depending on how stiff the nut is, the grip force required to stabilise the tool may be more or less than the grip force required to lock the pliers at the beginning. Thus, the relative contributions of the hand and the wrist change throughout the duration of the task, which would intuitively result in changes to muscle activity. This occurred in the present study for all three wrist flexors, whereby changes in task parameters (relative contributions from the hand and wrist) greatly altered wrist flexor muscle activity (Figure 3A, C and E). However, this effect was less obvious in the extensors, which demonstrated moderate-to-high levels of constant muscle activity across nearly all conditions. Similar to the report of Hägg and colleagues, the wrist extensors demonstrated few conditions of low muscle activity compared to the wrist flexors. For instance, despite the high combined effort of 60% in every experimental condition, FCR, FCU, and FDS exhibited muscle activity as low as 3.4 ± 0.9, 3.8 ± 0.6 and 5.4 ± 0.6% MVE, respectively, at certain points throughout the study. In comparison, the lowest muscle activity produced by ECR, ECU and ED was still as high as 9.0 ± 1.2, 15.2 ± 4.0 and 8.5 ± 0.8% MVE, respectively (2.6× more activity than the flexors). While muscle activity magnitudes were not statistically compared between the flexors and extensors in this study, any differences between these muscle groups would have manifested in co-contraction ratios. Two of the three forearm muscle pairings (FCR-ECR and FCU-ECU) demonstrated significantly more co-contraction during handgrip + wrist flexion conditions (driven by high antagonist wrist extensor muscle activity) compared to the handgrip + wrist extension conditions (antagonist wrist flexor activity was comparatively low).