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Craft techniques and minor accident damage
Published in Andrew Livesey, Alan Robinson, The Repair of Vehicle Bodies, 2018
Raising is another method of shaping metal by hand into a double-curvature shape. The method of raising is carried out by drawing the metal in courses over a suitably shaped steel stake or wood block, using floating blows which are struck slightly off the stake with a boxwood pear-shaped mallet. A series of blows is made in the metal starting at the centre, the blows being struck slightly off the stake. This has the effect of shrinking or reducing the circumference of the blank, thus forcing it down and around the stake. The disc or blank is rotated after each blow as in hollowing, but working from the centre in courses outwards towards the edges of the blank. The same process is repeated with frequent annealing of the metal until the final degree of raising is reached and the desired shape obtained. In the course of the raising, the edges of the metal around the circumference will be continually subjected to creasing, and care and skill are needed to avoid allowing these creases to become too sharp. If they are not worked out the edge will crack or fracture as the shape proceeds.
Differences in the rotational effect of buoyancy and trunk kinematics between front crawl and backstroke swimming
Published in Sports Biomechanics, 2021
Tomohiro Gonjo, Ricardo J. Fernandes, J. Paulo Vilas-Boas, Ross Sanders
The purpose of the present study was to investigate differences in the buoyant and hydrodynamic torque around the transverse axis between front crawl and backstroke swimming, and it was hypothesised that swimmers would show a larger magnitude of buoyant torque around the transverse axis in backstroke than in front crawl. A larger positive buoyant torque in front crawl than in backstroke at all trials clearly indicated that the leg-raising effect due to the buoyant torque is larger in front crawl regardless of the swimming velocity. Accordingly, swimmers produced a smaller negative hydrodynamic torque (a larger leg-sinking hydrodynamic torque) in front crawl than in backstroke to counterbalance the leg-raising buoyant torque. These results were counter to our initial hypothesis, and consequently, differences in the buoyant and hydrodynamic torque are not an explanation for a lower propulsive efficiency in backstroke than in front crawl (Gonjo et al., 2018, 2020).
How does buoyancy affect performance during a 200m maximum front crawl swim?
Published in Journal of Sports Sciences, 2018
Stelios G. Psycharakis, Toshimasa Yanai
As the CM and CB interaction is crucial in understanding the effects of buoyancy on swimming performance, consideration should be given to factors that might affect this interaction during swimming. For example, the time spent on arms’ recovery during a SC has not been reported in previous buoyancy studies. Recovery time would be useful in providing an indication of the percentage of the SC that the arms are submerged or above the water. Moreover, only minimum, maximum and average values for the overall leg-sinking or leg-raising effect of buoyant torque have been reported previously (Yanai, 2001). It would be interesting to know at which parts of the SC buoyant torque is directed to raise the legs or sink the legs, as well as how much time of the SC is spent at each of those two conditions. Furthermore, early studies in this area calculated buoyant torque for a mixture of breathing and non-breathing SCs, without controlling for or calculating the breathing effects (McLean & Hinrichs, 1998; Yanai, 2001). However, given that turning the head to take a breath is expected to alter the determined values of buoyant force and torque and swimming kinematics (Psycharakis & McCabe, 2011), such calculations may have masked the actual effects of buoyancy on performance. Thus, it is important that studies control for the effects of breathing on buoyancy calculations.
Improved uniformity of Ni/Au coating on circuits by electroless plating
Published in Surface Engineering, 2019
Dongguang Liu, Heng Tian, Lijing Lin, Wenchao Shi
Electroless nickel–gold plating technology is used to deposit nickel–gold coating on patterned circuits. The thickness of Ni/Au coating is about 3 µm. The self-oxidation of copper may cause the leakage deposition of Ni/Au coating. Ni2+ can be easily reduced and deposited on lines with the aid of excessive Pd catalysis, resulting in over plating. Pd particles are generated and deposited in situ, as Pd2+ reacts with free radicals or reduces functional groups produced by sensitive Sn2+. Ni/Au coating can be deposited around those bubbles with low catalytic activity instead of depositing Me ions. Enhancing the uniformity of the substrate materials and raising the annealing temperature can significantly decrease the number of pits.