Hysteresis measurement

Lin et al. [70, 71] have modeled the effect of surface roughness on the dependence of contact angles on drop size. Using two geometric models, concentric rings of cones and concentric conical crevices, they find that the effects of roughness may obscure the influence of line tension on the drop size variation of contact angle. Conversely, the presence of line tension may account for some of the drop size dependence of measured hysteresis. 

Ic. The Results of Stress-Temperature Measurements.—Hysteresis in the stress-strain behavior of rubber and rubberlike materials has presented the most serious problem encountered in the execution of otherwise simple experiments on the change of stress in stretched rubber with temperature at constant length (L) or at constant elonga-... 

For films formed at Ts below 405 (i.e. with grains below 5 nm) the measured hysteresis loops and the observations of the magnetic domains in applied magnetic fields seem to... 

Water isotherms determined at 35°C. are shown in Figure 3. The amount of water sorbed by the Pittsburgh coal is about twice the amount taken up by Pocahontas coal. These isotherms represent equilibrium measurements. Hysteresis loops that do not close at relative pressures less than 0.3 are characteristic of water adsorption on coal. 

Pr+ positive state of remanent polarization of the dynamically measured hysteresis loop... 

Figure 2, top, shows the T-dependent integrated intensity of the 451 peak. This peak is fee forbidden, and its intensity is therefore proportional to the square of the sc order parameter. Abut half the 0-K intensity is lost in a continuous precursor extending from 0 to Tc the remainder disappears much more abruptly at Tc 249 1 K. There is no measurable hysteresis, and no measurable cell volume change at Tc. These observations are all consistent with weakly first-order behavior. Scans of the range 2.7 A <4.5 A" at 230 and... 

If the relaxation is slow enough then magnetisation-applied field cycles can be performed to measure hysteresis loops (see later). In SMMs this slow relaxation is a result of the ZFS interactions in the ground spin state. Since magnetic anisotropy is being probed here, these measurements are ideally performed on single crystals. 

In the following we discuss measured hysteresis effects occurring in OFETs and in the corresponding MIS capacitors. For this purpose measurements are presented which are representative of the different devices prepared by us. 

Harwood and Payne (210) have demonstrated a simple, general relationship between the work input at break, Ub, and the hysteresis at break, Hb. The latter is defined as the area of the hysteresis loop formed between the extension and retraction branches of the strain curve, obtained in uniaxial tension at constant strain rate. Hb may be obtained by measuring hysteresis loops for various strain ranges (0 to e) and extrapolating the area of the loop to the breaking strain, eb. In a single experiment, the cross-head travel must be reversed just short of eb, which is not easily done in view of the stochastic nature of the failure process. The empirical relationship between Ub and Hb is... 

If there is measurable hysteresis, its time factor and thermal coefficient should be determined. The most difficult scenario is to have hysteresis that varies with amplitude, frequency, time, and temperature. Hysteresis requires detailed investigation when selecting transducers and amplifiers for a specific application. The limits should be verified for all likely circumstances, and possible failures should be identified. As well as hysteresis in the mechanical system, hysteresis in the amplifying circuit should be investigated. Fig. 7.12.2 shows that both kinds of hysteresis are possible. Hysteresis effects are caused by the following factors. 

In measuring hysteresis, two techniques for approaching the maximum and minimum contact angles were attempted. Once a bubble was formed on a plate it could be expanded or contracted until the base moved and measurements could be taken. Alternatively the bubble volume could be slowly increased or decreased and measurements taken until movement occurred. Both methods produced similar results but, when differences occurred, the greater level of hysteresis was associated with the latter procedure, owing probably to the duration necessary to complete the movement of the wetting phase along the solid surface. 

Fig. 7.1. Measured hysteresis in our reaction system [1]. Plot of the redox potential of Br, Fpt, as a function of the flow rate coefficient fct (in units of reciprocal residence times, the time spent by a volume element in the laminar flow reactor (LFR)). Filled dots represent one of the stable stationary states (the oxidized state) and empty dots the other stable state, the reduced state. Prom [1]...

Adsorption isotherms from Q% Hr were independent of whether the rock was initially dry or 100 % saturated or the number of subsequently measured hysteresis cycles. 

The isomorphous substitution of framework aliunimun in faujasite-type zeolites was evidenced by chemical analysis, XRD (unit cell contraction), mid-infra-red spectroscopy (shift of lattice vibrations) and adsorption measurements (hysteresis-free adsorption isotherms) [147] and later by Si MAS NMR spectroscopy [149,150,153] (see Fig. 5). 

Hau] Magnetie measurements Hysteresis loops at applied stress... 

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