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Abstract: The (CR–LR) difference technique, based on the CR-39 and LR 115 detectors, for the determination of implanted 210Po in glass after deposition of short-lived radon progeny, was analyzed in details in this paper. The sensitivities of both detectors were calculated using the Monte Carlo method with V functions particularly derived in our previous works for the detectors used in the present experiments. The dependency of the sensitivity ratio on the removed layer of both detectors was determined and verified experimentally. The simulated sensitivity ratios correlate well with the experimental ones. A major finding of the present work is that the sensitivity ratio between the CR-39 and LR 115 detectors depends only weakly on the ratio between the 238U and 232Th concentrations in the glass samples. This is crucial for the application of the (CR–LR) difference technique for retrospective radon exposure assessments, since measurements of the 238U and 232Th concentrations in the relatively small real-life glass samples will make the retrospective radon exposure assessments impractical. [Copyright &y& Elsevier]

In this paper, the reliability performance of uninterruptible power systems is studied. After the description of the protection system against anomalous conditions, a brief failure mode analysis is performed in order to define the fault tree referring to compensator output voltage. An analytical model able to deal with non-exponential life and repair time distributions is developed, using semi-Markov processes and assuming stochastic independence for the components of the system under study. The mean time between failure (MTBF) and the mean time to restoration of the compensator output voltage are then calculated exactly.Finally a mechanical bypass switch, which connects the load to the mains directly during long failures, is taken into account in the MTBF calculation via a simple approximation.Monte Carlo simulations are performed to validate the results of the analytical model and of the approximation. [Copyright &y& Elsevier]