[en] A physical model is proposed to describe the ground motion pattern resulting from an underground nulear explosion in an idealized homogeneous medium. Irregular behaviors in the observed ground motion are assumed to be perturbations caused by the local inhomogeneity of the ground medium. Our model correlates the ground motions at any point in the spalled zone to the initial acceleration pulse at the ground zero. Interestingly, the model predicts that the ground motion first comes to a stop at a definite radius about the ground zero, and the region expands both outward and inward as time goes on. We believe that this result is closely related to a phenomenon observed at NTS. In the far field approximation, we also calculate the overpressure in the lower atmosphere generated by the ground motion. We demonstrate that the irregular component of the ground motion does not affect the overpressure history in any significant way. Consequently the model ground motion can be used as a good approximation in generating the atmospheric overpressure

[en] The problem of retrieving the time dependence of the neutron energy spectrum from the detector current data in Faraday-cup experiments is studied. The time-dependent energy spectrum can be retrieved only when the neutron source in question meets a certain criterion. A detailed analytic formulation for the folding process is presented. The method that can be used to unfold the data in the retrievable case is explained in detail. 2 figures

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[en] Reliable cable systems are of utmost importance for electricity distribution- and grid networks. Cable terminations are key components of cable systems but also contribute significantly towards unwanted cable failures and power outages. Although well-developed standards exist in the electricity industry, it is not always possible to execute the most effective tests at power frequency due to financial or logistical reasons. Hence, withstand voltage- and Partial Discharge tests at power frequency are only conducted at a low percentage of electricity utilities. This paper presents the evaluation of unconventional partial discharge fault detection techniques and Very Low Frequency Tan Delta measurements on different cable termination defects. Five artificial cable termination defects were created on single core 6.35/11kV cross linked polyethylene cables, with one “defect-free” termination and five defective ones. Power frequency voltage was applied at increased voltage steps to initiate aging acceleration due to partial discharge. This resulted in insulation deterioration and eventual termination failure. Different data sets were obtained from the Very Low Frequency Tan Delta measurements as well as for the unconventional Partial Discharge measurements. The sequence of failures is compared between the two data sets and evaluated against the root cause failures of the terminations as evaluated by an industry expert. High Frequency Current Transformer and capacitive coupling sensors were used together with an advanced partial discharge data acquisition system. Partial discharge analysis was done to relate the specific on-line trending data with termination failure. Good correlation was found between the two data sets which supports the utilization of unconventional partial discharge measurement for cable acceptance testing. It would be beneficial for the electricity industry to consider unconventional Partial Discharge technology as a suitable alternative for on-site acceptance tests for cable terminations. (authors)