Effect of errors on the efficiency of local active sound absorbers

Effect of errors of different origin on the efficiency of sound absorption by a local active absorber is investigated. Degradation of the efficiency of absorption because of the errors is shown to be minimal in the case when the controller does not detect the field of the secondary radiator. Estimates of admissible errors are presented. Several active absorber configurations in which the radiator does not affect the receiver are considered.     

Effect of crack tip sharpness on the strength of vulcanized rubbers

The effect of crack tip sharpness on crack propagation in vulcanized rubbers has been studied. For very sharp cracks, tearing is found to occur on a small scale at very low energies not far above the threshold required for the onset of mechanical crack growth. The “small-scale” tearing energies show relatively little variation for rubbers that differ widely in tear strength as normally measured. Thus the latter property appears to be strongly influenced by variations in the ability of rubbers to promote tip blunting. The small-scale tear behavior is of relevance to other fracture phenomena, including cutting by sharp objects and tensile failure. Natural variations in tip sharpness occur during cyclic or time-dependent mechanical crack growth and influence the form of the crack growth characteristics.     

Ion structure determinations and ion—molecule reactions by double quadrupole mass spectrometry

The QQ mass spectrometer is shown to be applicable to ion structure determination via collision-induced dissociations of mass-selected ions. The instrument can be scanned so as to record the products of dissociation as well as those of ion—molecule association reactions. The dissociations correspond to those observed at high kinetic energy in mass-analyzed ion kinetic energy spectrometers and the association reactions show parallels with reactions seen in ion cyclotron resonance spectroscopy and in high-pressure mass spectrometry