Development of Methods for Navigational Referencing of Circumlunar Spacecrafts to the Selenocentric Dynamic Coordinate System     

Andreev  A. O.  Nefedyev  Yu. A.  Demina  N. Yu.  Nefediev  L. A.  Petrova  N. K.  Zagidullin  A. A. 《Astronomy Reports》2020,64(9):795-803

Astronomy Reports - The initial form of present-day space optical observations contain considerable geometrical and brightness distortions. This problem can be solved based on geometrical...  相似文献   

Physical Libration of the Moon: An Extended Problem     

Zagidullin  A. A.  Usanin  V. S.  Petrova  N. K.  Nefedyev  Yu. A.  Andreev  A. O.  Gudkova  T. V. 《Astronomy Reports》2020,64(12):1093-1106

Astronomy Reports - The work is devoted to the study of the physical libration of the Moon. Interest in the traditional topic related to the rotation of the Moon is stirred up by the activity of...  相似文献   

Prospects for Estimating the Properties of a Loose Surface from the Phase Profiles of Polarization and Intensity of the Scattered Light     

Petrova  E. V.  Tishkovets  V. P.  Nelson  R. M.  Boryta  M. D. 《Solar System Research》2019,53(3):172-180

It has been shown that the model of a scattering medium composed of clusters located in the far zones of each other allows some properties of regolith-like surfaces to be quantitatively estimated from the phase dependences of intensity and polarization measured in the backscattering domain. From the polarization profiles, the sizes of particles, the structure and porosity of the medium, and a portion of the surface area covered with a disperse material can be determined. At the same time, the intensity profiles of the scattered light weakly depend on the sizes and structure of particles; they are mainly controlled by the concentration of scatterers in the medium and the shadow-hiding contribution at small phase angles. Since the latter effect is beyond the considered model, a good agreement between the model and the measured intensity cannot be achieved. Nevertheless, if a portion of the surface that participates in coherent backscattering has been found from the phase profile of polarization, the present model makes it possible to determine the relative contribution of the shadow-hiding effect to the brightness surge measured at zero phase angle. This, in turn, may allow the roughness of the scattering surface to be estimated. The model contains no free parameters, but there is currently no possibility to verify it comprehensively by the data obtained in laboratory measurements of the samples with thoroughly controlled characteristics, because such measurements are rare for a wide range of the properties of particles in a medium, their packing density, and phase angles.

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Study of the properties of artificial composite materials for permeable geochemical barriers     

N. N. Danchenko  M. L. Kuleshova  Z. P. Malashenko  E. V. Petrova  V. I. Sergeev 《Moscow University Geology Bulletin》2011,66(5):354-360

We study the filtering and sorption parameters of laboratory-produced composite materials, such as sand-gels, sand-gels with an FeS activating additive, peat-gels, and commercial sorbents on the basis of cellulose coated with MnO₂, which can be used for production of permeable geochemical barriers. The carry over and the efficiency of consumption of the active component are estimated for materials with activating additives. It is shown that all the materials under study can be used as fillers for a permeable geochemical barrier, but each of them has its own limitations.  相似文献   

On the adequacy of second-order models to predict abnormal waves     

P. Petrova  Z. Cherneva  C. Guedes Soares   《Ocean Engineering》2007,34(7):956-961

The paper is intended to extend the investigations about the nature of abnormal waves that have been reported in the work of Guedes Soares et al. (Characteristics of abnormal waves in North Sea states. Applied Ocean Research 25, [337–344]). The same dataset gathered at the oil platform North Alwyn in the North Sea during the November storm in 1997 is used along with the time series from the Draupner platform, in which an abnormal wave occurred. The data are reanalyzed from the viewpoint of the applicability of second-order models to fit large waves. The observed results confirm that the second-order approximation is not adequate to describe highly asymmetric and abnormal waves.  相似文献   

Petroleum-related hydrocarbons in deep and subsurface sediments from South-Western Barents Sea     

Boitsov S  Petrova V  Jensen HK  Kursheva A  Litvinenko I  Chen Y  Klungsøyr J 《Marine environmental research》2011,71(5):357-368

Subsurface sediments from a pockmark area in South-Western Barents Sea have been earlier found to contain elevated levels of petroleum-related polycyclic aromatic hydrocarbons. This work describes a comprehensive analysis of various biomarkers, including the highly source-specific hopanes, in a 4.5?m long gravity core from the same area, together with subsurface sediment samples from other areas in the region without pockmarks present ("background samples"). A clear difference between the pockmark gravity core and the background sediment cores was found, both with regard to genesis and the level of transformation of organic matter. A number of indicator parameters, such as methylphenanthrene index (MPI-1), point towards a significantly higher maturity of hydrocarbons in the pockmark core throughout its length as compared to the other sampled locations. Higher contents of microbial hopanoids (hopenes) may indicate the former presence of petroleum. These findings confirm the hypothesis of a natural hydrocarbon source in the deeper strata present in the studied location with pockmarks.  相似文献   

The ionospheric effects in D-layer and solar proton precipitation zones during the 16 February 1984 event     

M. I. Beloglazov  G. P. Beloglazova  E. V. Vashenyuk  G. A. Petrova  O. I. Shumilov  V. A. Shishaev

I. N. Zabavina

V. I. Nesterov 《Planetary and Space Science》1990,38(12):1479-1486

The results of the geophysical and VLF (10–16 kHz) radio propagation measurements on the net of observatories during the solar proton event on 16 February 1984 are analysed. It is shown that the abnormal ionization region caused by solar protons consisted of two parts. One of them was the direct access zone in the middle and morning side of the polar cap, the other was the precipitation region of the quasi-trapped particles in the mid-day and evening sectors of the auroral zone. The probable profiles of the lower ionosphere electron density are determined from the VLF and satellite data of the energetic spectra at the maximum penetration. It is shown that the effective electron concentration at the height 45 km was close to 10³ cm⁻³.  相似文献   

Polarization transfer in a pulsar magnetosphere     

S. A. Petrova 《Monthly notices of the Royal Astronomical Society》2006,366(4):1539-1550

Propagation of radio waves in the ultrarelativistic magnetized electron–positron plasma of a pulsar magnetosphere is considered. The polarization state of the original natural waves is found to vary markedly on account of the wave mode coupling and cyclotron absorption. The change is most pronounced when the regions of mode coupling and cyclotron resonance approximately coincide. In cases when the wave mode coupling occurs above and below the resonance region, the resultant polarization appears essentially distinct. The main result of the paper is that in the former case the polarization modes become non-orthogonal. The analytical treatment of the equations of polarization transfer is accompanied by numerical calculations. The observational consequences of polarization evolution in pulsar plasma are discussed as well.  相似文献   

The intrinsic shapes of galaxy groups     

V.V. Orlov  A.V. Petrova  V.G. Tarantaev 《Monthly notices of the Royal Astronomical Society》2001,325(1):133-137

The intrinsic, three-dimensional shapes of small galaxy groups, containing between three and eight members, are evaluated using three different statistics: (i) the mean sum of square sines of angles in all possible triangles formed by members of the group; (ii) the variance of square paired separations in the group; (iii) the axial ratio of a rectangle containing the group. The mean values of these parameters and their rms deviations are calculated for observed galaxy groups and simulated groups with members that are distributed randomly within prolate or oblate spheroids. Comparison of observational data and simulations shows that the observed galaxy groups have shapes consistent with the projected shapes of prolate or oblate spheroids with axial ratios of 3:1, regardless of their multiplicity, but inconsistent with the projected shapes of spherical objects.  相似文献   

Neoproterozoic Volhynia-Brest magmatic province in the western East European craton: Within-plate magmatism in an ancient suture zone     

A. A. Nosova  O. F. Kuz’menkova  N. V. Veretennikov  L. G. Petrova  L. K. Levsky 《Petrology》2008,16(2):105-135

The reasons for the isotopic and geochemical heterogeneity of magmatism of the Neoproterozoic large Volhynia-Brest igneous province (VBP) are considered. The province was formed at 550 Ma in response to the break up of the Rodinia supercontinent and extends along the western margin of the East European craton, being discordant to the Paleoproterozoic mobile zone that separates Sarmatia and Fennoscandia and the Mesoproterozoic Volhynia-Orsha aulacogen. The basalts of VBP show prominent spatiotemporal geochemical zoning. Based on petrographic, mineralogical, geochemical, and isotopic data, the following types of basalts can be distinguished: olivine-normative subalkaline basalts consisting of low-Ti (sLT, < 1.10–2.0 wt % TiO₂; ε_Nd(550) from ?6.6 to ?2.7) and medium-Ti (sMT, 2.0–3.0 wt % TiO₂, occasionally up to 3.6 wt % TiO₂; ε_Nd(550) from ?3.55 to + 0.6) varieties; normal quartz-normative basalts (tholeiites) including low-Ti (tLT, < 1.75–2.0 wt % TiO₂) and medium-to-high-Ti (tHT1, 2.0–3.6 wt % TiO₂, ε_Nd(550) from ?1.3 to + 1.0) varieties. The hypabyssal bodies are made up of subalkaline low-Ti olivine dolerites (LT, 1.2–1.5 wt % TiO₂; ε_Nd(550) = ?5.8) and subalkaline high-Ti olivine gabbrodolerites (HT2, 3.0–4.5 wt % TiO₂; ε_Nd(550) = ?2.5). Felsic rocks of VBP are classed as volcanic rocks of normal (andesidacites, dacites, and rhyodacites) and subalkaline (trachyrhyodacites) series with TiO₂ 0.72–0.77 wt% and ε_Nd(550) of ?12. The central part of VBP is underlain by a Paleoproterozoic domain formed by continent-arc accretion and contains widespread sills of HT2 dolerites and lavas of LT basalts; the northern part of the province is underlain by the juvenile Paleoproterozoic crust dominated by MT and HT1 basalts. MT and LT basalts underwent significant AFC-style upper crustal contamination. During their long residence in the upper crustal magmatic chambers, the basaltic melts fractionated and caused notable heating of the wall rocks and, correspondingly, nonmodal melting of the upper crustal protolith containing high-Rb phase (biotite), thus producing the most felsic rocks of the province. The basalts of VBP were derived from geochemically different sources: probably, the lithosphere and a deep-seated plume (PREMA type). The HT2 dolerites were generated mainly from a lithospheric source: by 3–4% melting of the geochemically enriched garnet lherzolite mantle. LT dolerites were obtained by partial melting of the modally metasomatized mantle containing volatile-bearing phases. The concepts of VBP formation were summarized in the model of three-stage plume-lithosphere interaction.  相似文献