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1
Content available remote Ionospheric perturbations: a case study of 2007 five major earthquakes using DEMETER data
Thomas Jewel Emem, Ekanem Aniekan Martin, George Nyakno Jimmy, Akpan Anthony Effiong
Acta Geophysica
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2023
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Vol. 71, no. 4
1607--1618
EN
Using the Plasma analyzer (IAP) and Langmuir Probe (ISL) experiments of the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) lithospheric–atmospheric–ionospheric coupling has been observed before, during and after five major earthquakes with magnitudes greater than 6.5. The aim of this study is to use ionospheric parameters to identify the ionospheric perturbations associated with the five earthquake regions screened. All the three investigated ionospheric parameters of electron density, electron temperature and total ion density recorded perturbations within the investigative period. A total of 36 anomalies were obtained with 18 each for nighttime and daytime readings. The observed anomalies being screened for false alarm using the geomagnetic indices of Kernnifzer digit (kp) and disturbance storm time (Dst.) revealed 27.8% as geomagnetically induced perturbations. Thus, 72.2% of the studied anomalies transpired in quiet geomagnetic conditions, which is linked to seismic events.
2
Perturbations on K-fusion frames
Bhandari Animesh, Mukherjee Saikat
Journal of Applied Analysis
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2021
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Vol. 27, nr 2
175--185
EN
Fusion frames are widely studied for their applications in recovering signals from large data. These are proved to be very useful in many areas, for example, wireless sensor networks. In this paper, we discuss a generalization of fusion frames, K-fusion frames. K-fusion frames provide decompositions of a Hilbert space into atomic subspaces with respect to a bounded linear operator. This article studies various kinds of properties of K-fusion frames. Several perturbation results on K-fusion frames are formulated and analyzed.
3
Content available remote A Study of Early/Slow VLF Perturbations Observed at Agra, India
Pandey U., Singh A. K., Singh O. P., Singh B., Saraswat K.
Acta Geophysica
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2016
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Vol. 64, no. 3
755--771
EN
We present here the results of sub-ionospheric VLF perturbations observed on NWC (19.8 kHz) transmitter signal propagating in the Earth-ionosphere waveguide, monitored at our low latitude station Agra. During the period of observation (June-December 2011), we found 89 cases of VLF perturbation, while only 73 cases showing early character associated with strong lightning discharges. Out of 73 events, 64 (~84%) of the early VLF perturbations are found to be early/slow in nature; the remaining 9 events are early/fast. The onset duration of these early/slow VLF perturbations is up to ~ 5 s. A total of 54 observed early events show amplitude change lying between ± 3.0 dB, and phase change ± 12 degree, respectively, and found to occur mainly during nighttime. One of the interesting results we found is that the events with larger recovery time lie far away from the VLF propagation path, while events with smaller duration of recovery are within the ± 50-100 km of signal path. The World Wide Lightning Location Network (WWLLN) data is analysed to find the location of causative lightning and temporal variation. The lightning discharge and associated processes that lead to early VLF events are discussed.
4
Perturbations of the matrix logarithm
Gil' M.
Journal of Applied Analysis
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2012
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Vol. 18, nr 1
47-68
EN
The paper suggests sharp norm estimates for the matrix logarithm and for the difference of the logarithms of two matrices.
5
Content available remote Perturbation method in the analysis of manipulator inertial vibrations
Szumiński P.
Mechanics and Mechanical Engineering
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2011
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Vol. 15, nr 2
149-160
EN
An analysis of inertial component of mechanical vibrations induced during a motion of the MAR industrial manipulator is presented. The mathematical analysis of vibrations is based on the perturbation method. The presented considerations include an analytical description of inertial vibrations as well as results of the numerical analysis for the RPP-type manipulator.
6
Content available remote GOCE satellite orbit in the aspect of selected gravitational perturbations
Bobojć A., Drożyner A.
Acta Geophysica
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2011
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Vol. 59, no. 2
428-452
EN
In this work, the GOCE satellite orbit is described in the aspect of perturbations in the Keplerian osculating elements. The perturbations come from the Earth and ocean tides, the gravitation of the Moon, the gravitation of the Sun, the gravitation of planets and Pluto, and the relativity effects. These perturbations are computed for the 30-day interval with a sampling of 2 min. To obtain the simulated orbit, the Cowell numerical integration method of 8th order is used. The first part of the work contains the root mean square (RMS) values of aforementioned perturbations due to the specified forces. The perturbations were compared taking into account their RMS characteristics. Perturbations in elements of the GOCE osculating orbit are also presented on the plots for successive epochs of the 30-day interval. Changes of the obtained perturbations were described and their characteristic periodic components were distinguished.
7
Content available remote Multiscaling analysis of a nonlinear boundary value problem in lubrication theory
Aliu E., Shepherd J. J., Connell H. J.
International Journal of Applied Mechanics and Engineering
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2004
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Vol. 9, no 3
455-470
EN
The method of multiple scales, a long standing alternative to the method of matched expansions, is applied to the nonlinear boundary value problem modelling the operation of a one-dimensional gas lubricated slider bearing, at large values of the bearing number. Approximate expansions for the pressure profile, load bearing capacity and the location of the centre of pressure are obtained, and compared with the results of applying matched expansions and numerical techniques.
8
Content available remote Tensor products of one-parametric operator groups: unbounded perturbation
Zima P., Łopuszański O.
Czasopismo Techniczne. Środowisko
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2004
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R. 101, z. 9-Ś
153--158
EN
The formula for decomposition in a series for an unbounded perturbation of tensor products of one-parameter operator groups on Banach spaces is presented.
PL
W pracy został wprowadzony wzór na rozwinięcie nieograniczonych zaburzeń iloczynu tensorowego jednoparametrowych grup operatorów w przestrzeniach Banacha.
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