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The electrical resistivity and induced polarization (IP) methods are widely used in geological mapping, prospecting and exploration of mineral deposits, engineering geology, hydrogeology, archaeology, and geotechnical and environmental applications. Historically, these methods have formed the basis of the electrical prospecting technique. In these methods, a DC or low-frequency AC electrical current is introduced into the earth through a grounded transmitter line. The measured quantity is the electric field. However, if the earth’s resistivity or chargeability changes horizontally, this change gives rise to an anomalous magnetic field, which is studied by the magnetometric resistivity (MMR) and magnetic induced polarization (MIP) methods, respectively. Along with advantages, some shortcomings are inherent in the MMR and MIP techniques. Apparently, the main drawback of these methods is that the magnetic fields of both the transmitter line wire and ground electrodes on the surface are several orders of magnitude greater than the anomalous magnetic field response. This introduces a significant “noise” to magnetic-resistivity data. We investigate the potential of using a circular electric dipole (CED) in magnetometric resistivity techniques. It has been found that the application of a CED, instead of a conventional transmitter line, dramatically enhances the signal-to-noise ratio. 相似文献
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Transient electromagnetic (TEM), self-potential (SP) and geoelectrical mapping measurements were carried out at the Chernorud-Mukhor site in the Priolkhonje area on the western shore of the Lake Baikal. All measurements were made along several profiles across the main strike of the regional Primorsky fault. TEM measurements were carried out in a time range from a few tens of microseconds to several tens of milliseconds. The most important result of the 1D modelling of TEM soundings is the discovery of nearly horizontal boundaries that divide high resistive overlying and well conducting underlying rocks. The resistivity of the former is in the range from 100 Ωm to 1000 Ωm, while the resistivity of the latter varies from less than 1 Ωm to several tens of Ωm. This good conductive zone could also be verified by geoelectrical mapping using Schlumberger array (AB/2=100 m). Due to high conductivity of the underlying rocks only the upper boundary of the conductive layer could be determined by TEM soundings. A regional SP anomaly with amplitude of about −450 mV has also been observed above the low resistivity zone indicating the electron nature of its conductance. Geologically, the conductive zone is represented by a graphite-bearing layer within the region of archean rocks. Since that layer extends over a large area, it may be used as a key in studying structures and tectonics of the Priolkhonje area. A 1D TEM geoelectric section shows a wide, gently sloping syncline as a probable base structure of the Chernorud-Mukhor site. Neotectonic faults divide the syncline into vertically displaced blocks that form a wide complicated graben with a total amplitude of about 250 m. 相似文献
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V. P. Kozhevnikov 《Astronomy Letters》2010,36(8):554-568
Recently, it has been shown that the cataclysmic variable EI UMa should be attributed to intermediate polars on the basis
of its X-ray spectrum. However, no short-period oscillations with a high degree of coherence typical of intermediate polars
could be detected in this star. Therefore, it was suggested to call it a “hidden” intermediate polar. Using a multichannel
photometer and a 70-cm telescope, we performed observations of EI UMa for 60 h. Analysis of the observations has clearly revealed
a brightness oscillation with a period of 769.63±0.10 s and a mean semiamplitude of 0·
m
008 completely coherent during one month of our observations that was detectable during each of the 13 observing nights. On
the basis of this detection, EI UMa should be considered a classical intermediate polar rather than a hidden one. In addition,
we have managed to detect the orbital variability of EI UMa for the first time. The orbital light curve is extremely interesting,
showing evidence of partial eclipses of the accretion flow. 相似文献
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V. N. Kozhevnikov S. G. Skublov Yu. B. Marin P. V. Medvedev Yu. Systra V. Valencia 《Doklady Earth Sciences》2010,431(1):318-323
Using local procedures, the new results on the isotope ages and composition of mineral inclusions were obtained for detrital
zircons from Paleoproterozoic Jatulian terrigenous quartzites and polymictic conglomerates in Central and Western Karelia.
For Eastern Laurasia, signs of the existence of Hadean and ancient Eoarchean matter were found for the first time (zircon
grains of 3871 ± 38.6 and 3837 ± 42.1 Ma concordant ages). The multimodal distribution of ages within 3.45−2.61 Ga was revealed.
The discovery of the oldest zircon grains provides the conditions for valid global correlations of geological events that
determined the deposition and formation of the continental crust of the North Atlantic supercraton. 相似文献
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V. P. Kozhevnikov 《Astrophysics and Space Science》2014,349(1):361-371
We report results of photometry of the suspected V Sge star IPHAS J025827.88+635234.9. The observations were obtained over 25 nights in 2011 and 2012. The total duration of the observations was 153 h. We discovered eclipses typical of cataclysmic variables and flickering, which is also a hallmark of cataclysmic variables. These discoveries characterise this star as a normal cataclysmic variable but not as a star of the V Sge type, as was previously supposed. The eclipse period is equal to 5.882274±0.000008 h. Its depth is equal to 0.3 mag. The full eclipse width is quite large and equal to $(0.160\pm0.011)P_{\rm orb}$ . We obtained an eclipse ephemerid with a formal shelf life of about 500 yr (a 1σ confidence level). This ephemerid is good for investigations of long-term period changes. The eclipse has a complicated two-component V-shaped profile. This profile suggests that the accretion disc is very structured and can consist of an extended disc halo and a quite distinct central part. The off-eclipse light curve is also complicated. It shows two orbital humps at the orbital phases 0.4 and 0.9 and a deep depression at the orbital phase 0.14. By using the period-luminosity-colours relation found by Ak et al., we estimate the distance of this star in the range 660–730 pc. The corresponding absolute visual magnitude is roughly by 1 mag brighter than that for an average cataclysmic variable with the same orbital period. The noted unusual properties of the eclipse profile and off-eclipse light curve can be related with this enlarged luminosity. 相似文献
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V.P. Kozhevnikov 《New Astronomy》2012,17(1):38-42
The cataclysmic variable V378 Peg is known since 15 years. Although V378 Peg is a rather bright star (14 mag), it underwent no detailed study. We performed photometric observations of V378 Peg during 75 h with the goal to detect periodic brightness variations. The obtained light-curves clearly showed changes with a period of about 3 h. The Fourier analysis reveals that this oscillation occurs with a period of 3.238 h and a semiamplitude of 0.07 mag. Although the detected oscillation possesses certain coherence, it appears to have a slightly unstable period or phase. Therefore, the detected period cannot be the orbital period of the V378 Peg system. Because such instability is typical of superhumps, we must consider the detected oscillation as superhumps. Furthermore, V378 Peg shows no outbursts and has to be a nova-like variable rather than a dwarf nova. Hence, the detected superhumps have to be regarded as permanent superhumps. Because superhump periods in cataclysmic variables are close to orbital periods, we can find the place of V378 Peg in the orbital period distribution of cataclysmic variables. V378 Peg is a permanent superhump system above the upper edge of the 2-3 h period gap in the orbital period distribution. 相似文献
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Doklady Earth Sciences - Wavy spatial variations in the contents of trace gases are identified using plane measurements of O3 concentrations in the medium troposphere and the total content (TC) of... 相似文献
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A. V. Kozhevnikova V. P. Kozhevnikov I. Yu. Alekseev I. A. Yushkov A. A. Dorogov 《Astronomy Reports》2012,56(4):281-289
We present the results of new multicolor photometry of the chromospherically active binary CG Cyg acquired in 2005–2009 (136
hours of observations). The light curves for each season reveal rotational brightness modulation due to spots that varies
in amplitude and phase from season to season. We have determined the longitudes of spotted areas: for each season, they were
located on the primary, close to the line joining the centers of the components. The longitude distribution of spots was analyzed
for 44 years of observations of CG Cyg using all data available in the literature. The active longitudes of CG Cyg are not
fixed at the quadratures, as was believed earlier: most of the time (1965–2003), the spots were concentrated at two active
longitudes at the quadratures, at orbital phases 0.28±0.06 and 0.70±0.08, but, during a shorter time after 2004, they were
located along the line joining the component centers, at orbital phases 0.50 ± 0.04 and 0.93 ± 0.03. We detected a switch
of the active longitude by 180° during 1.5 months in 2008, accompanied by an increase in the amplitude of the rotational brightness
modulation and only a slight increase in the star’s spotted area (by 5%). Our analysis of archive data reveals that switches
of the active longitude during time intervals of 1–1.5 months were observed three times during the entire observational history
of CG Cyg (in 1991, as well as in our observations of 2003 and 2008). All these switches were accompanied by similar phenomena:
an increase in the amplitude of the rotational brightness modulation (by 0.06
m
, 0.02
m
, and 0.04
m
) and an increase in the spotted area (by 79%, 11%, and 5%). We used a zonal spot model to reconstruct the parameters of the
spotted regions on CG Cyg. At all our observing epochs, the spots were located at low latitudes, in a region that was symmetric
about the equator, 10° to 14° wide on either side. The spots are cooler than the surrounding photosphere by 2000 K. The spotted
area varied only slightly from season to season, comprising 13%–15% of the surface area of the star, close to the historic
spottedness maximum for the CG Cyg system. 相似文献