Cross-over distortion

EXERCISE 6-1Q Find the harmonics contained in the cross-over distortion of a push-pull amplifier. Let the input to the amplifier be a 2 V amplitude, 1 kHz sine wave. The push-pull amplifier drives an 8 Q load. 

Cross-over distortion in Class B amplifiers [Sinclair, 1989]. 

The transfer of the electron takes place very rapidly compared to nuclear motion, and will only take place when the combination of internal and librational coordinates is such that the curves interact. Thus, the [Fe(H20)6] + species must first distort and/or experience a dipole moment field from the instantaneous positions of the water molecules such that it attains the cross-over point. At this point, the electron may tunnel from the [Fe(H20)6]2+ ion to the metal, leaving behind an [Fe(H20)6]3 + ion with a non-equilibrium geometry, This then relaxes by heat transfer to the solvent to the equilibrium point, q0. 

Certain simplifications that allow the dynamic response to be reconciled with equivalent static loadings are examined. In earthquake loading the dominant effects are found to occur in the lowest mode for which no cross sectional distortion takes place. In wind loading the dynamic response is spread over several modes. The maximum dynamic tensile stresses at the windward base of the tower can be estimated using simple gust effect factors. 20 refs, cited. 

As previously noted, spin cross-over behaviour is well established in iron(II) complexes and there are also examples involving iron(III) species. For example, a variety of iron(III) dithiocarbamate complexes of the type [Fe(S2CNR2)3j having a trigonally distorted octahedral geometry display high-spin/low-spin cross-over behviour 49,50 Little is known about the spin forbidden d-d transitions of iron(III) complexes due to near-UV charge transfer bands that tail into the visible part of the spectrum. Even simple iron(III) salts in aqueous media are yellow. 

The psychological effects of LSD are especially dramatic. Users experience hallucinations and distortions of reality. People on LSD may become confused or anxious, or they may feel euphoric. They may feel several different emotions at once or have intense and rapid mood swings. Many people report that colors seem more vivid and that their senses seem to "cross over"—that is, users feel as if they can "taste" colors or "see" sounds. For some people, these altered perceptions are terrifying, and they may try to escape from the imaginary dangers they perceive. In a few cases, people have accidentally died while they were high on LSD. 

Deflection of the electron beams in a color CRT represents a difficult technical exercise. The main problems that occur when the three beams are deflected by a common deflection system are associated with the spot distortions that occur in single-beam tubes. However, the effect is intensified by the need for the three beams to cross over and combine as a spot on the shadow mask. The two most significant effects are curvature of field and astigmatism. 

When straight or serrated segmental weirs are used in a column of circiilar cross secdion, a correction may be needed for the distorted pattern of flow at the ends of the weirs, depending on liquid flow rate. The correction factor F from Fig. 14-33 is used direcdly in Eq. (14-112) or Eq. (14-119). Even when circular downcomers are utilized, they are often fed by the overflow from a segmental weir. When the weir crest over a straight segmental weir is less than 6 mm V in), it is desirable to use a serrated (notched) weir to provide good liquid distribution. Inasmuch as fabrication standards permit the tray to be 3 mm Vh in) out of level, weir crests less than 6 mm V in) can result in maldistribution of hquid flow. 

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