The Green function for M oscillotor with antiwmmuting degrees of freedom is obtained by extending two operator methods to the case of a Grassmann algebra: the dynamicalgroup approach md the Dira-Schwinger method. In both methods. we verify that the canonical anticommutation relations are responsible for the fact that this system has a negative-dimensional behaviour.
In order to obtain information on the degradation of solar cells in artificial satellites as a result of cosmic ray radiations, positron annihilation lifetime experiments were performed for B-doped p-type Czochralski (CZ) silicon wafers irradiated at room temperature with 1 MeV electrons with fluences between 10 14 and 10 17 e/cm 2 . Positron lifetime measurements were done at 100 K to improve the trapping rates of positrons with defects. The mean lifetime of irradiated Si was shorter than that of unirradiated Si. We found that short lifetime defects (approximately 100 ps) existed, which could be associated with complexes of Si with interstitial oxygen atoms, doped B and vacancies resulting from irradiation. Lifetime components longer than those of the bulk accounted for the formation of thermal donors and divacancies.
Numerical instabilities hamper the computer simulation of axially symmetric, three-dimensional transient discharges from proceeding (Davies et al 1977).In the present paper, a method is presented in which suppression of the instabilities is attempted by avoiding numerical differentiation. The results when the present method is applied to simulation of a narrow, high-overvoltage discharge observed by Chalmers et al (1972) show that this method enables one to trace the cathode streamer reaching the cathode and the subsequent fronts propagating. The formation of the so-called radial constriction of the streamer is discussed.
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