Hysteretic

The petroleum oils are of three basic types aromatic, naphthemic, and paraffinic. Aromatic oils contain hazardous materials that require special handling precautions. Naphthenic oil does not contain hazardous levels of polynuclear aromatics (PNAs) and is less hysteretic. Because of these considerations the naphthenic oil is gaining in usage at the expense of more utilized aromatics. Paraffinic oil is only used modestly in tire compounds. The... 

Hysteretic whirl. This type of whirl occurs in flexible rotors and results from shrink fits. When a radial deflection is imposed on a shaft, a neutralstrain axis is induced normal to the direction of flexure. From first-order considerations, the neutral-stress axis is coincident with the neutral-strain axis, and a restoring force is developed perpendicular to the neutral-stress axis. The restoring force is then parallel to and opposing the induced force. In actuality, internal friction exists in the shaft, which causes a phase shift in the stress. The result is that the neutral-strain axis and neutral-stress axis are displaced so that the resultant force is not parallel to the deflection. The... 

Figure 5-22a. Hysteretic whirl. (Ehrich, F.F., Identification and Avoidance of Instabilities and Self-Excited Vibrations in Rotating Machinery, Adopted from ASME Paper 72-DE-21, General Electric Co., Aircraft Engine Group, Group Engineering Division, May 11, 1972.)...

One last form of voltage-mode eontrol is very rudimentary. It eould be ealled hysteretic voltage-mode. In this form of eontrol, a fixed frequency oscillator is gated ON only when the output voltage has fallen to below a limit dictated by the voltage feedback loop. It is sometimes called hiccup-mode because the power switch occasionally bursts on and then returns to a constant off state. 

Another form current-mode control is called hysteretic current-mode control. Here both the peak and the valley currents are controlled. This is obviously better for continuous-mode forward for boost converters. It is somewhat complicated to set-up, but it does offer very fast response times. It is not a very common method of control and its frequency varies. 

However, we are increasingly confronted with practical problems that involve material response that is inelastic, hysteretic, and rate dependent combined with loading which is transient in nature. These problems include, for instance, structural response to moving or impulsive loads, all the areas of ballistics (internal, external, and terminal), contact stresses under high speed operations, high... 

Constant deflection amplitude fatigue testing is probably the less demanding of the two techniques, because any decay in the modulus of elasticity of the material due to hysteretic heating would lead to lower material stress at the fixed maximum specimen deflection. In the constant load amplitude tests, maximum material stress is fixed, regardless of any decay in the modulus of elasticity of the material. 

A more detailed study has looked at the stmctural model of cross-linked E-plastomers. The purpose of this study was to develop correlations between dynamic properties such as the hysteretic loss and compression set of E-plastomers with key microstmctural variables such as density and molecular weight. 

The incorporation of reinforcing hllers into rubber results in most cases in an increase of the storage and loss moduli, G and G", and an increase in hysteresis, as quantihed by the loss angle 8, where tan 8 is C jG. When properly dispersed and coupled to the mbber matrix via a coupling agent, as represented by a low Payne effect, silica also shows less hysteretic loss at elevated temperatures. 

MillyPCD. Moisture and heat transport in hysteretic, inhomogeneous porous media anatric head based formulation and a numerical model. 1982 Water Resource Research 18(3) 489 98. 

Author s Comments The first company representative seems to have dished out the stock reply on reducing output ripple in conventional (PWM) regulators. But his second point is a fairly good run-down on capacitors in general. However, the 2621 is a hysteretic controller and therefore depends on output ripple to behave. So the advice doesn t really apply. 

Looking at the blog entry that follows, this one is technically correct if rather peremptorily explained. Hysteretic controllers are actually quite simple. In Chapter 2 we discussed the leverage factor of a voltage divider. In this case the reference is 1.24V and Vom is 3.8V. So the leverage factor is 3.8/1.24 = 3.0645. So... 

Author s Comments Many PCB layout guides seem to think it is physically possible to put every component right next to the IC (overlapping ). Without any help from your Physics professor on how to increase the number of spatial dimensions, your best chance here is to create a priority list, that is, which component takes precedence over the other. Layout has been discussed in great detail in previous chapters, and it should be consulted. Though, unfortunately, hysteretic ICs such as the 2621 are even harder to design in a layout, and still are often unpredictable. 

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