We have performed a geophysical search for fractionally charged particles in seawater and rock samples. The samples were run through cation exchange columns to separate most of the material from particles of charge =bf and =bJ. The purified samples were converted into azides and evaporated in an electron gun, which accelerated the negatively charged particles to a solid-state detector. Quarks with charge +f (#i) would probably evaporate from azides as (#i+e) and would thus have an effective charge of -J. The pulseheight spectra from the detector were scanned for peaks corresponding to particles of a charge between -1 and 0; no such particles were found. Limits on the concentration of qi quarks are
The jet from a nominally axisymmetric shaped charge is formed by the collapse of the typically conical liner under the high pressures resulting from detonation of the explosive around it. Where asymmetries are present the velocities imparted to the elements of the liner at a given axial distance from the cone tip will vary as a function of the azimuthal angle among other variables. In general these elements will not meet at all. Conversely a pair of liner elements that do meet will in general have started from different axial positions, and will meet away from the nominal axis of symmetry of the charge. This effect renders the formation process asymmetrical. Consequently the jet particles have an off-axis velocity component which can substantially degrade the penetrative capability of the charge. A complete analysis of asymmetrical liner collapse and jet formation is presented for the case where the liner is axisymmetric, but there is an azimuthal variation in liner projection velocity. The classical analysis of symmetric liner collapse and jet formation is extended to include this type of asymmetry. Earlier work on linear shaped charges, particularly a model for asymmetric jet formation, is drawn upon to consider plane sections of the liner individually. A fully three-dimensional analysis is then achieved by the combination of the results for these sections. This analysis is implemented in a computational model and example results are presented and compared in as far as is possible and meaningful with previous theoretical and experimental results. Good agreement with the previous theoretical work is obtained, and the values of the off-axis velocity components predicted are of the orders observed in the limited experimental data as yet available.
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