Seismicity accompanying mining exploitation results from changes in the stress field in the rock mass near the mining excavations caused by human activity. Many studies of the temporal and spatial ...distribution of mining induced seismicity have provided evidence for interrelations among events. Although a variety of techniques have been applied to quantify the interdependences of mining induced seismic events, the physical mechanism of interactions has not been unequivocally identified. Based on the premise that one possible cause of interactions among seismic events can be static stress transfer, we have verified statistically the role of Coulomb stress transfer in the generation process of mining induced seismicity using a series of seismic events that occurred in the Rudna mine in the Legnica-Głogów Copper District in Poland. We quantify the triggering and inhibiting effect by the proportion of events in the series, whose locations are consistent with the stress increased and stress decreased zones, respectively. We have found that more than 60 per cent of the analysed seismic events occurred in areas where stress was enhanced due to the occurrence of previous events. The statistical significance of these results is tested by comparing them with the same proportions obtained for 2000 random permutations of the original series of events. The test has indicated that the locations in positive stress changes areas are preferred statistically significantly when the stress changes exceed 0.05 bar. This result turns out to be robust to the errors of the nodal planes determination.
We use a high‐quality data set from the NW part of The Geysers geothermal field to determine statistical significance of temporal static stress drop variations and their relation to injection rate ...changes. We use a group of 322 seismic events which occurred in the proximity of Prati‐9 and Prati‐29 injection wells to examine the influence of parameters such as moment magnitude, focal mechanism, hypocentral depth, and normalized hypocentral distances from open‐hole sections of injection wells on static stress drop changes. Our results indicate that (1) static stress drop variations in time are statistically significant, (2) statistically significant static stress drop changes are inversely related to injection rate fluctuations. Therefore, it is highly expected that static stress drop of seismic events is influenced by pore pressure in underground fluid injection conditions and depends on the effective normal stress and strength of the medium.
Key Points
We examined significance of temporal static stress drop changes in relation to injection rate variations at The Geysers geothermal field
Variations of static stress drop in time are statistically significant
Changes of static stress drop are inversely related to injection rate fluctuations
•Design, modelling and prototype of the novel Axial Active Magnetic Bearing.•Validated analytical model is convergent with experiments and numerical simulation.•Schwarz-Christoffel transformation is ...utilized in study of the actuator end effect.•Three-dimensional complex permeance function represents the stator pole pieces.•Computational time of analytical model is significantly shorter then numerical one.
The article presents a novel design of the axial active magnetic bearing with six poles. An analytical magnetic bearing model was developed to provide the axial magnetic induction distribution in 3D. The model utilizes magnetic vector potential formulation and Schwarz-Christoffel mapping. The paper covers in-depth deliberations on the end effect influence and the conjugate complex permeance function. Numerical model and simulations were provided in 3D mode with support of COMSOL Multiphysics software. The six pole axial active magnetic bearing was manufactured and investigated experimentally. Identification of the magnetic field distribution was carried out with a single axis magnetic induction sensor using custom automatic field scanner. High convergence of the modeling results and experimental research was demonstrated. The main advantage of the proposed analytical method is significantly shorter computation time compared to the numerical one that is useful from the modeling and controller study point of view. The configuration, modeling, simulation and experimental investigation results are well illustrated for the better overview.
Spatial and temporal evolution of the stress field in the seismically active and well-monitored area of the western Gulf of Corinth, Greece, is investigated. The highly accurate and vast regional ...catalogues were used for inverting seismicity rate changes into stress variation using a rate/state-dependent friction model. After explicitly determining the physical quantities incorporated in the model (characteristic relaxation time, fault constitutive parameters, and reference seismicity rates), we looked for stress changes across space and over time and their possible association with earthquake clustering and fault interactions. We focused our attention on the Efpalio doublet of January 2010 (
M
= 5.5 and
M
= 5.4), with a high aftershock productivity, and attempted to reproduce and interpret stress changes prior to and after the initiation of this seismicity burst. The spatial distribution of stress changes was evaluated after smoothing the seismological data by means of a probability density function (PDF). The inverted stress calculations were compared with the calculations derived from an independent approach (elastic dislocation model) and this comparison was quantified. The results of the two methods are in good agreement (up to 80 %) in the far field, with the inversion technique providing more robust results in the near field, where they are more sensitive to the uncertainties of coseismic slip distribution. It is worth mentioning that the stress inversion model proved to be a very sensitive stress meter, able to detect even small stress changes correlated with spatio–temporal earthquake clustering. Data analysis was attempted from 1975 onwards to simulate the stress changes associated with stronger earthquakes over a longer time span. This approach revealed that only
M
> 5.5 events induce considerable stress variations, although in some cases there was no evidence for such stress changes even after an
M
> 5.5 earthquake.
Quill mites are obligatory parasites of birds, widely distributed among their hosts. For the first time, we examined birds from two small, phylogenetically closely related piciform families, ...Megalaimidae (New World Barbets) and Capitonidae (Asian Barbets), for infestation by parasitic mites of the subfamily Picobiinae (Acariformes: Syringophilidae). Birds of the family Megalaimidae were infested by two new species of the genus Picobia: Picobia insolita Skoracki, Sikora & Unsoeld n. sp. collected from Caloramphus hayii in Indonesia, and Picobia paraheeri Skoracki, Sikora & Unsoeld n. sp. found on nine bird species of the genus Psilopogon, including P. zeylanicus in Sri Lanka, P. asiaticus in India, P. virens in China, P. franklini and P. lineatus both in Nepal, and P. corvinus, P. rafflesii, P. chrysopogon, P. pyrolophus, all in Indonesia. Within the Capitonidae family, a single quill mite species, Rafapicobia olszanowskii Skoracki et al. 2020, was found infesting two species of the genus Capito, i.e. C. maculicoronatus in Panama and C. niger in Surinam and Guyana, and these two Asian Barbet species are new hosts for this quill mite species. Our further analysis of picobiine mite records associated with the entire order of Piciformes revealed a correlation between the mites’ distribution patterns and the phylogeny of piciform birds. This significant congruence suggests a close evolutionary relationship between picobiine mites and their avian hosts.http://zoobank.org/urn:lsid:zoobank.org:pub:F9DEB980-6481-4229-A071-52AC9FF69879http://zoobank.org/urn:lsid:zoobank.org:act:6B4F98EB-D166-4DBF-B26F-49F4B22903A8http://zoobank.org/urn:lsid:zoobank.org:act:98140DAC-5C53-438B-85A6-1FBA52D178D0
A theoretical description of the g factor of a muon bound in a nuclear potential is presented. One-loop self-energy and multiloop vacuum polarization corrections are calculated, taking into account ...the interaction with the binding potential exactly. Nuclear effects on the bound-muon g factor are also evaluated. We put forward the measurement of the bound-muon g factor via the continuous Stern-Gerlach effect as an independent means to determine the muon’s magnetic moment anomaly and mass. The scheme presented enables the increase of the accuracy of the mass by more than an order of magnitude.
The g factor of highly charged ions Harman, Z; Sikora, B; Yerokhin, V A ...
Journal of physics. Conference series,
11/2018, Volume:
1138, Issue:
1
Journal Article
Peer reviewed
Open access
Recent years have witnessed a remarkable improvement in the theoretical description of bound-electron g factors, paralleled with a quantum jump in the experimental accuracy in the investigation of ...these quantities. In the present article we give a brief summary of the latest developments, with emphasis on the influence of quantum electrodynamic and nuclear effects on the g factor of few-electron highly charged ions, and on the possible determination of fundamental constants.
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