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121.
Average velocity field of the air flow over the water surface in a laboratory modeling of storm and hurricane conditions in the ocean 总被引:1,自引:0,他引:1
A. A. Kandaurov Yu. I. Troitskaya D. A. Sergeev M. I. Vdovin G. A. Baidakov 《Izvestiya Atmospheric and Oceanic Physics》2014,50(4):399-410
Laboratory experiments on studying the structure of the turbulent air boundary layer over waves were carried out at the Wind-Wave Channel of the Institute of Applied Physics, Russian Academy of Sciences (IAP RAS), in conditions modeling the near-water boundary layer of the atmosphere under strong and hurricane winds and the equivalent wind velocities from 10 to 48 m/s at the standard height of 10 m. A modified technique of Particle Image Velocimetry (PIV) was used to obtain turbulent pulsation averaged velocity fields of the air flow over the water surface curved by a wave and average profiles of the wind velocity. The measurements showed that the logarithmic part of the velocity profile of the air flow in the channel was observed in the immediate vicinity from the water surface (at a distance of 30 mm) and could be detected only using remote methods (PIV). According to the measured velocity profiles, dependences of aerodynamic drag factors of the water surface on the wind velocity at a height of 10 m were retrieved; they were compared with results of contact measurements carried out earlier on the same setup. It is shown that they agree with an accuracy of up to 20%; at moderate and strong wind velocities the coincidence falls within the experimental accuracy. 相似文献
122.
We present new results of our visual (V, R, I) and near-infrared (J,H,K) photometry for the unusual young star V718 Per. They show that, in addition to prolonged eclipses following one another
with a period of 4.7 yr, the star also exhibits low-amplitude brightness oscillations with a period that is approximately
a factor of 8 shorter than the main one. In contrast to the large-scale eclipses accompanied by the star’s reddening, the
low-amplitude oscillations are neutral in character and are produced by large particles. Bimodal oscillations of this type
can arise in a circumstellar disk divided by a large matter-free gap into two zones—an inner, dense region and an outer, less
dense disk. Such configurations emerge in the presence of a fairly massive perturbing body in the disk. In this case, density
waves rotating with different angular velocities can be formed in each of these zones. Therefore, when such systems are observed
nearly edge-on, two oscillation modes with different periods can be present in the extinction variations. We suggest that
such a situation takes place in the case of V718 Per. Since this star exhibits no signatures of spectroscopic binarity, the
perturbing body can be either a giant planet or a brown dwarf. 相似文献
123.
V. T. Doroshenko S. G. Sergeev Yu. S. Efimov S. A. Klimanov S. V. Nazarov 《Astronomy Letters》2009,35(6):361-374
Based on our UBV RI observations and X-ray data from the RXTE satellite, we have investigated the variability of the galaxy 3C 120 over the period 1996–2008. The relative variability amplitude in the U and B bands without any subtraction of the contribution from the underlying galaxy is 23 and 22%, respectively, against 21% in the X-ray band. The autocorrelation function based on the B-band data is considerably wider than that based on the X-ray data. The structure functions on a time scale from 1 to ~100–300 days in the X-ray and optical spectral ranges have the form of a power law (SF ~ τ b ). However, their indices differ significantly: b = 0.42 in the X-ray band and b = 1.36 in the B band. Considering the X-ray and optical variabilities as a superposition of independent flares in a wide range of durations, we may conclude that the amplitudes of short flares in the X-ray band are higher than those in the optical one and, conversely, the relative amplitudes of long flares in the X-ray band are slightly lower than those in the optical one, i.e., short events dominate in the X-ray band. The optical flux variations in the R c and I c bands lag significantly behind those in the B band, by 3.9 ?0.7 +1.0 and 6.2 ?0.6 +1.1 days, respectively, if the lag is estimated from the centroid of the cross-correlation function. The X-ray variability on a time scale of about 1800 days (~5 yr) lags behind the B-band variations by 5.3 ?3.3 +2.7 days, but the confidence level of this estimate is only 87%. A more detailed analysis of the correlation between the X-ray and optical emissions has revealed a fairly complex picture: different degrees of correlation between the optical and X-ray fluxes are observed at different times. 相似文献
124.
A ca. 600 m thick siliciclastic succession in northern Russia contains abundant and diverse microfossils that document early to middle Ediacaran deposition along the northeastern margin of the East European Platform. The Vychegda Formation is poorly exposed but is well documented by a core drilled in the Timan trough region (Kel’tminskaya-1 borehole). Vychegda siliciclastics lie unconformably above Tonian to lower Cryogenian strata and below equivalents of the late Ediacaran Redkino succession that is widely distributed across the platform. The basal 10 m of the formation preserve acritarchs and fragments of problematic macrofossils known elsewhere only from pre-Sturtian successions. In contrast, the upper, nearly 400 m of the succession contains abundant and diverse large acanthomorphic acritarchs attributable to the Ediacaran Complex Acanthomorph Palynoflora (ECAP). This distinctive set of taxa is known elsewhere only from lower, but not lowermost, Ediacaran rocks. In between lies an additional assemblage of relatively simple filaments and stratigraphically long ranging sphaeromorphic acritarchs interpreted as early Ediacaran in age. Bearing in mind that knowledge of late Cryogenian (post-Strurtian/pre-Marinoan) microfossils is sparse, the Vychegda record is consistent with data from Australia and China which suggest that diverse ECAP microfossil assemblages appeared well into the Ediacaran Period. Accumulating paleontological observations underscore both the promise and challenges for the biostratigraphic characterization of the early Ediacaran Period. 相似文献
125.
126.
M. V. Luchitskaya A. V. Moiseev S. D. Sokolov M. I. Tuchkova S. A. Sergeev P. B. O’Sullivan V. E. Verzhbitskii N. A. Malyshev 《Geotectonics》2017,51(1):17-39
The paper presents new data on the U–Pb zircon age, as well as results of isotopic geochemical analysis, of granites and rhyolites from Wrangel Island. The U–Pb age estimates of granites and rhyolites are grouped into two clusters (~690–730 and 590–610 Ma), which imply that these rocks crystallized in the Late Neoproterozoic. Granitic rocks dated back to 690–730 Ma are characterized by negative εNd(t) values and Paleoproterozoic Sm–Nd model age. The older inherited zircons corroborate the ancient age of their crustal source. The granitic rocks pertain to involved peraluminous granites of type I, which form at a continental margin of the Andean type and can be compared with coeval granites and orthogneisses from the Seward Peninsula in Alaska. Rhyolites and granites ~590–610 Ma in age are distinguished by a moderately positive εNd(t) and Mesoproterozoic model age. It is suggested that they have a heterogeneous magma source comprising crustal and mantle components. The geochemical features of granites and rhyolites correspond to type A granites. Together with coeval OIB-type basalts, they make up a riftogenic bimodal association of igneous rocks, which are comparable with orthogneisses (565 Ma) and gabbroic rocks (540 Ma) of Seward Peninsula in Alaska. 相似文献
127.
V. I. Sergeev M. L. Kuleshova A. Yu. Bychkov N. N. Danchenko T. G. Shimko 《Moscow University Geology Bulletin》2017,72(2):143-152
The soil sorption properties were determined for the base of ash storage at a proposed power station on Sakhalin Island. The analyses of aqueous extracts of the coal ashes that are intended for use at the station resulted in the identification of potential pollutant elements that might be transferred with the infiltrate of atmospheric precipitation. The composition of the infiltrate-modeling solution was selected based on the data. The sorption capacity of the covering soil by identified pollutants was evaluated at static and dynamic conditions, along with the degree of potential desorption of these pollutants. 相似文献
128.
V. L. Andreichev K. V. Kulikova A. N. Larionov S. A. Sergeev 《Doklady Earth Sciences》2017,477(1):1260-1264
The granitic magmatism occurred at the precollisional stage of the continentalization of the mafic basement of the Shchuch’ya island arc system. The first U–Pb (SIMS, SHRIMP II) data on zircons indicate three pulses of transformation of the oceanic crust into a continental crust: in the Silurian and Middle and Late Devonian. The age of the Yanganape granite is 429 ± 4 Ma, which corresponds to the Late Wenlockian; that of the Yurmeneku massif is 385 ± 2 Ma (Givetian); and that of the Canyon Massif is 368 ± 3 Ma (Famennian). The zircons from the Yanganape granite yielded an age of 335 ± 4 Ma, which corresponds to the Early Carboniferous (Visean). Similar ages were noted in uranium-rich zircons from the Canyon Massif granite. They correlate with the collision time of the island arc with the eastern edge of the Eastern European paleocontinent, and it is possible that this event caused disturbance of the U–Pb system of zircons in the islandarc granites of the Shchuch’ya zone. 相似文献
129.
S. B. Lobach-Zhuchenko Sh. K. Baltybaev V. A. Glebovitsky S. A. Sergeev K. O. Lokhov Yu. S. Egorova V. V. Balagansky S. G. Skublov O. L. Galankina L. M. Stepanyuk 《Doklady Earth Sciences》2017,477(2):1391-1395
Complex study of the U–Pb and Lu–Hf systems of zircon from a lhertzolite lens of Archean gneiss enderbites of the Bug complex, Ukrainian Shield, showed that ultramafic magma was contaminated by the material of the country gneiss enderbites. The age of the zircons of 2.81 ± 0.05 Ga corresponds to the period of ultramafic magmatism within the Bug complex. Previously, this peak of endogenic activity was considered the stage of manifestation of metamorphism and magmatism of mafic composition. 相似文献
130.
Lobach-Zhuchenko S. B. Kaulina T. V. Marin Yu. B. Yurchenko A. V. Skublov S. G. Egorova Yu. S. Galankina O. L. Sergeev S. A. 《Doklady Earth Sciences》2019,484(1):101-104
Doklady Earth Sciences - Data on the U–Pb (SIMS SHRIMP-II) age (3628 ± 38 and 2845 ± 65 Ma) of zircon from the inclusion of mafic granulite in gneiss–enderbites of the Bug... 相似文献