Resistivity peaks

Figure 6.39 Variation of the % magnetoresistance with . Inset shows the variation of the peak resistivity, p, at (After Mahesh et al, 1995).

The magnitude of GMR itself increases with an increase in the peak resistivity (at T M). In other words, one needs a bad metal to observe good GMR. Furthermore, even formally antiferromagnetic compositions (jc > 0.5) show GMR because of the presence of ferromagnetic clusters. 

Oscillator circuits are a cost-efficient alternative to impedance analysis and ring-down [12,13]. Naturally, most sensors rim on oscillator circuits. Some advanced circuits provide a measure of the dissipation (such as the peak resistance, Ri, see Sect. 6) in addition to the frequency. Most oscillators operate on one harmonic only. Oscillators can be more stable than ring-down and impedance analysis because the latter two techniques periodically turn the crystal on and off in one way or another, whereas oscillators just run quietly on one fixed frequency. If the signal-to-noise ratio is the primary concern, no technique can beat oscillators. There is one pitfall with the use of oscillators worth mentioning the theory below pertains to the series resonance frequency (simply called resonance frequency). The output frequency of an oscillator circuit, on the other hand, usually is not the series resonance frequency (Fig. 2). For instance, phase-locked-loop oscillators keep the phase constant. Many oscillators run at the zero-phase frequency (B = 0, Fig. 2). Importantly, the difference between the zero-phase frequency and the series resonance frequency changes if the bandwidth or the parallel capacitance change (Sect. 6). The... 

A necessary connection between the traditional impact experiments and more definitive and quantitative methods of fracture mechanics was made by Plati and Williams (1975a, 1975b) for cases of moderate plastic response of small-scale yielding (SSY) and accounted for yielding, whereby the measured impact-fracture work could be related to the size of the fracture area by consideration of the character of the deformation geometry of the bent bar and the crack-tip field. For a standard Izod or Charpy geometry as shown, e.g., for the Izod experiment depicted in Fig. 12.23, Plati and Williams considered the connection for two forms of approach that were based on measurement of the peak resistive force. Pc, or on measurement of the work of fracture W. 

Equation 28.15 is a prediction that is derived from load-independent assumptions, and is therefore expected to hold in the face of load variation. As load varies, the maximum driving force (kxj and peak-resistive force (cEp ai ), derived by PDF analysis from the changing E-wave contours, may change, but the... 

As follows from the data of work [37], the characteristic feature of the microstructure of the LajcMn03+5 samples with x = 0.815 and 0.90 is the presence of simply connected domains containing a number of grains. The porosity of these samples does not exceed 7 %. In both the cases, the peak resistivity is comparable to the values which were observed in polycrystalline samples for which the negligible role of tunneling effects was proved experimentally [26,62,63]. All these facts imply that for the Lo.gis and L0.90 samples, the porosity affects the absolute value of resistivity but hardly modifies its temperature dependence. For the other samples, however, the role of porosity as well as the contribution of tunneling effects to the conductivity should be discussed separately. This will be done below while discussing the resistivity of the L0.94 sample. 

DDT resistant insects have the ability to convert DDT to a less toxic substance called DDE The mass spectrum of DDE shows a cluster of peaks for the molecular ion at m/z 316 318 320 322 and 324 Suggest a reasonable structure for DDE... 

Fig. 4. Selection of fan size where the soHd line represents a typical setting and the dashed lines the operating extremes, (a) Desirable sizing. The system resistance curve intersects the fan curve near its maximum efficiency. Changes in system resistance from a flow-control element also intersect the fan curve at desirable points for good flow control. The dashed curves also intersect system resistance curves at desirable locations, (b) A fan essentially too large for the system. The intersection of the system curve near the peak of the fan curve results in poor system flow control and perhaps surging.

Thermal Resistance and Flammability. Thermal analysis of PVA filament yam shows an endothermic curve that starts rising at around 220°C the endothermic peak (melting point) is 240°C, varying afitde depending on manufacture conditions. When exposed to temperatures exceeding 220°C, the fiber properties change irreversibly. 

Coriolis-Type Flow Meters. In CorioHs-type flow meters the fluid passes through a flow tube being electromechanically vibrated at its natural frequency. The fluid is first accelerated as it moves toward the point of peak vibration ampHtude and is then decelerated as it moves from the point of peak ampHtude. This creates a force on the inlet side of the tube in resistance to the acceleration and an opposite force on the outlet side resisting the deceleration. The result of these forces is an angular deflection or twisting of the flow tube that is directly proportional to the mass flow rate through the tube. 

Appllca.tlons. The principal appHcations of nickel-base superalloys are in gas turbines, where they are utilized as blades, disks, and sheet metal parts. Abcraft gas turbines utilized in both commercial and military service depend upon superalloys for parts exposed to peak metal temperatures in excess of 1000°C. Typical gas turbine engines produced in the United States in 1990 utilized nickel and cobalt-base superalloys for 46% of total engine weight (41). However, programs for future aerospace propulsion systems emphasize the need for lightweight materials having greater heat resistance. For such apphcations, intermetallics matrix composites and ceramic composites are expected to be needed. 

Optimum surface roughness usually is 0.05—0.5 pm a very smooth surface contains very Htde lubricant within its depressions, whereas rough peaks penetrate the lubricant to promote wear. Improved corrosion resistance may be obtained with a suitable subcoating surface conversion treatment or by inclusion of inhibitors in the coating. 

Fig. 6. Calculated siUcon resistivity vs temperature for the impurity (doping) levels shown, where (—) is -type, (------), n-ty e. Left of the peaks is the...

---