Sharp Contact Resistance

The transfer curve of an ideal device that would exactly follow these equations is drawn in Fig. 5, together with its first and second derivative. The first derivative is a step function, while the second derivative reduces to a sharp peak at Vg = Vx, thus allowing a precise and reliable estimation of the threshold voltage [22-24]. A major interest of the method is that it is not sensitive to both gate voltage dependence and contact resistance. 

Cell Assembly In terms of the compression pressure on the fuel cell, there are initially high benefits to increased compression and reduced contact resistance. Think of a stack loosely held together by gravity. Contact losses would obviously be high, as shown in Figure 4.31. As the compression is increased, there is a plateau region where optimal contact pressure is reached. If the compression is increased too far beyond this level, however, the components in the fuel cell will suffer plastic (permanent) deformation and cause a very sharp drop-off... 

In practice, it may be possible with care to float somewhat larger particles than those corresponding to the theoretical maximum. As illustrated in Fig. XIII-7, if the particle has an irregular shape, it will tend to float such that the three-phase contact occurs at an asperity since the particle would have to be depressed considerably for the line of contact to advance further. The resistance to rounding a sharp edge has been investigated by Mason and co-workers [62]. 

Spreading resistance—the resistance between the deep interior of a semiconductor and a very sharp metal point pressed on the surface— measures the local resistivity on a scale of the order of the contact radius (Ehrstein, 1974). It thus measures the amount of hydrogen taking part in donor or acceptor passivation, whether this occurs by complex formation or by compensation. However, some methods of preparing samples for a spreading resistance measurement may involve heating above room temperature, and this may cause redistribution even of hydrogen bound in some types of complexes (Mu et al., 1986). 

Stainless steels exhibit the best resistance to corrosion when the surface is oxidized to a passive state. This condition can be obtained, at least temporarily, by a so-called passivation operation in which the surface is treated with nitric acid and then rinsed with water. Localized corrosion can occur at places where foreign material collects, such as in scratches, crevices, or comers. Consequently, mars or scratches should be avoided, and the equipment design should specify a minimum of sharp comers, seams, and joints. Stainless steels show great susceptibility to stress corrosion cracking. As one example, stress plus contact with small concentrations of halides can result in failure of the metal wall. 

Ionomer (Surlyn) is a methacrylic acid and ethylene modified molecule with a metal ion (sodium, zinc, magnesium). Easy sealing, soft, strong, grease-resistant clear film, and seals well in contact with contaminants. Puncture-resistant, with a high hot tack. Approximately double the price of LDPE, but can be used in thinner gauges. Can be used in the inner ply of laminates, at approx, gauge of LDPE and as a skin pack over sharp or pointed objects. 

The multi-sensing technologj-, based on simultaneous high-resolution force and electrical and acoustic measurements, allows for ver> accurate determination of both delamination/ adhesion and scratch resistance of both thin and thick coatings. Using the test tools with higher contact area (or length), like micro-blade or ball, may allow for more repeatable results than those obtained with sharp styluses. 

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