Predicting the time of rock bursts in the INGEO system is based on the analysis of seismic emission registered in a seismic-acoustic system. Emission signals are generated by rock mass fracturing due to mining exploitation. Such emission is characterized by huge activity of different phenomena which enables to carry out a correct statistical analysis with the use of the hazard method, achieving suitably high resolution of interpretation results. The hazard method is based on the analysis of maximal phenomena, i.e. phenomena of maximal energy. The use of this method allows to eliminate disturbances to a large extent and, at the same time, enables to assess the probability of high-energy phenomena (rock bursts). The hazard analysis is conducted on the basis of two essential qualities of seismic emission, such as energy of phenomena and intervals between successive phenomena. These qualities are random variables of statistical distribution described by the Weibull model. Using this model one can estimate the parameters of statistical distribution of those qualities which are the basis to determine hazard parameters. The analysis is conducted based on measurement data collected from the T window, i.e. time interval measured by hours. The window is moved with the d step and the calculations are repeated. The hazard parameters were used to define the risk function FWt(QE,T) which is the measure of rock bursts hazard. This function depends on real time t which is determined as the time of the T window right edge. It is also the basis to work out rock burst hazard criteria. It is important to note that the moment a rock burst occurs is a random variable and can be determined with the accuracy of its confidence interval, with certain probability.
In the article the authors investigated a field-oriented control system with a slip-ring shaded-pole motor. Additive disturbing signals were introduced into input signals of the control system controllers. The rotational speed waveform was observed as an output of the system. Disturbing signals were sine-wave signals with known frequency. The field-oriented control system was parametrically optimized with the use of an evolutionary algorithm. The testing was carried out with the use of the MATLAB/Simulink software.
The article features deliberations concerning the analysis of the following in the homomorphism of processes: deformations corresponding to the medium (rock mass) vibrations which generate physical threats in the subarea of topological transformations. Here, the basic issue is deformation mapping applied to model the dislocation processes related to the paraseismic process. Time dependencies are characterized by structure and dynamics of the processes. The damage of the part of the rock mass near the exploited deposit causes deformations and, most frequently, topological transformation of successive layers. Quite often rock bursts are generated, which is related mainly to the exceeded boundary states of the medium. Here it is very important to have measuring information about the medium transformations. In addition, it is necessary to define parameters and measures that characterize the anisotropy of the rock mass structures. The research within the INGEO project was focused on solutions based on the adaptation of the parabolic differential description supported by monitoring a concrete physical dislocation process. The mapping state of the process trajectory was distinguished in the deformation space by means of mathematical algorithms. Numerical modelling of deformation fields was supported by GPS sensors (innovative direct monitoring), on-line GNSS technology, and compaction sensors with a view to measuring complex dislocation fields. This solution is a new technology. A parametrically optimized model adequately illustrates a standard (measurement results) layout of vertical dislocations.
Experience acquired for a number of years proves that the fluidity of production processes in longwalls depends on proper support of the excavation roof. A properly matched power support unit is not enough to guarantee good support of the excavation roof, particularly in its face part. Irregularities in the maintenance of the longwall roof may be related to some errors in the control of the power support unit, mainly in setting the unit with too low initial pressure. With respect to the above issues, the article features an analysis of the setting load impact on the bearing capacity of props in a power support unit.
Insulation systems and electric contacts of electric power switches are components that are damaged most often. The electric strength to the breakdown of the electric switch contact gap is measured by the electric field intensity and the corresponding voltage at which the breakdown of the system occurs. The breakdown of the contact gap is fostered by the heterogeneity of voltage gradient. Electric contact systems in the process of currents conduction or switching are the most loaded heat elements of the current paths. They should be designed, constructed and operated in such a way that during the conduction of operating currents the prescribed value of the temperature rise limit should not be exceeded and that the contacts should not weld or deform permanently during the conduction of fault currents. The paper presents examples how to use analytical and numerical methods to evaluate the heterogeneity degree of the electric field in the contact gap. In addition, appropriate mathematical relations were given to estimate the value of the contact gap breakdown voltage. Finally, the paper discusses the factors influencing the ampacity of the contacts during the conduction of operating and short-circuit currents.
The article features the results of research in the field of welding high-strength rails. The scope of the research combined not only monitoring of the welding process as such but also the assessment of the achieved results. The recommendations how to carry out welding operations are part of the results too.