A Study of Non-Gravitational Effects of Comet C/1995 O1 HALE–BOPP

The role of non-gravitational forces in the evolution of orbitalmotion of C/1995 O1 (Hale–Bopp) has been investigated. Inorbital calculations the observational material covering theperiod from April 1993 up to August 2001 was used. To model thenon-gravitational acceleration, observed and theoretical profilesof the H₂O production rates were employed. A set of forcedprecession models of a rotating cometary nucleus consistent withthe observed spin axis orientation was fitted to positionalobservations. The non-gravitational models allowed us to constrainthe mass and radius of the comet. The orbitalevolution of Comet Hale–Bopp was investigated over ±400 k yusing two sets of randomly varied orbital elements wellrepresenting all positional observations in the pure gravitationalcase, as well as in the non-gravitational case. The calculationsshowed that the comet's motion is predictable only over an interval ofa few orbital periods. The statistical conclusions changesignificantly when non-gravitational effects are included in the analysis.     

Effect of partial mining of shaft protection pillar in terms of reliability index

ABSTRACT

The work presents calculations of shaft support reliability index during partial extraction of protection pillar deposit and the related seismic phenomena. It has been assumed that the probability of failure caused by seismic phenomena depends on the velocity random variable of the shaft support vibrations. The random vibration velocity is a function of random variables of energy, shock distance and vibration frequency. Estimations of probability distributions for energy and frequency have been based on the actual measurement data from a mine. Failure probability has been estimated by means of methods based on so-called Hasofer-Lind reliability index β.     

Deep Electrical Resistivity Structure of the European Lithosphere in Poland Derived from 3-D Inversion of Magnetotelluric Data

Surveys in Geophysics - This paper presents a three-dimensional (3-D) model of the resistivity distribution in the European lithosphere at the junction between the East European Craton, the...     

Effectiveness of Random Field Approach in Serviceability Limit State Analysis of Strip Foundation

Geotechnical and Geological Engineering - This work conducts a probabilistic inquiry on how the variability of the parameter defining soil deformability affects the settlement of the foundation...     

Snow Accumulation on a Small High‐Arctic Glacier Svenbreen: Variability and Topographic Controls

One of the main controls on the net mass change of land‐terminating Arctic glaciers is the magnitude and distribution of snow accumulation. In Dickson Land, region of Svalbard with the greatest distance to the sea, the issue has not been receiving much scientific attention for decades. In this paper, new snow accumulation data are presented from Svenbreen in Dickson Land from end‐of‐winter surveys. The measured winter balance was 0.42 ± 0.15 m w.e. in 2010, 0.50 ± 0.10 m w.e. in 2011 and 0.62 ± 0.10 cm w.e. in 2012. Snow depth and water equivalent have been analysed in the background of altitude, slope and aspect extracted from the digital elevation model of the glacier. On steep northern slopes (>15°) accumulation was the highest, whereas it was decreased on southern slopes with moderate inclination (9–12°). Elevation, which on many glaciers proved to be highly correlated with snow depth, explained only 17–34% of snow depth variability due to complex interplay between local climate and geometry of a small valley.