A global isostatic gravity model of the Earth   总被引：3，自引：0，他引：3  

Mikhail K. Kaban  Peter Schwintzer  & Sergey A. Tikhotsky 《Geophysical Journal International》1999,136(3):519-536

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Using the end-member mixing approach to apportion sources of polycyclic aromatic hydrocarbons in various environmental compartments     

Mikhail Yu. Semenov  Irina I. Marinaite 《Environmental Earth Sciences》2016,75(3):207

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Decrease in the clear air transmission at Helwan Observatory site     

J. S. Mikhail  B. B. Baghos  M. Y. Tawadrous  Y. E. Helali  H. Awad  KH. I. Khalil  M. El-Saftawe  M. Ibrahim 《Earth, Moon, and Planets》1995,70(1-3):143-149

Clear air atmospheric transparency of eight nights at Helwan Observatory site during autumn period of 1987 have been determined using the yellow filter GG5. The prevailing atmospheric transmission extends to 58%. A comparison with previous values obtained with the same filter and site during autumn period of 1963 shows a considerable decrease at the present years in the clear air transmission of the site of Helwan. This can be attributed to the aerosol pollution of the site caused mainly by the increase of the industrial centers at Helwan Zone. Clear air atmospheric transparency values at the beginning of winter season and at spring season are also given.  相似文献   

Light pollution and night sky brightness at the site of Kottamia Observatory     

S. Nawar  A. B. Morcos  J. S. Mikhail 《Earth, Moon, and Planets》1995,70(1-3):133-141

Photoelectric measurements of the night sky brightness and the light pollution of Kottamia Observatory have been carried out and the deduced results are expressed in mag/sec². The maximum brightness of the sky in the direction of Cairo city at zenith distance 45° and azimuth 70° when the sun is almost 60° below the horizon are 22.68; 21.54 and 19.82 mag/sec² for blue, yellow and red colours respectively. The corresponding values of night sky background are 22.94; 21.85 and 20.14 mag/sec² respectively.The isophotes of the sky brightness at Kottamia Observatory have been drawn for blue, yellow and red colours. The variations of the night sky brightness and the (B-V) colour index with altitude of the observed point have been studied.The light pollution and the night sky brightness at the site of Kottamia Observatory is compared with that deduced by different investigators at other sites. It has been shown that the sky brightness at zenith distance 45° at Kottamia Observatory site is similar to Kitt Peak and Palomar Observatory sites. Kottamia Observatory site is slightly brighter than Junipero Serra while it is darker than Mount Hamilton and San Jose sites. The comparative results have been carried out at blue and yellow colours. No comparison is obtained at red as there is no data published for the red colour.  相似文献   

Mineralogy and petrography of amoeboid olivine aggregates from the reduced CV3 chondrites Efremovka,Leoville and Vigarano: Products of nebular condensation,accretion and annealing     

Mutsumi KOMATSU  Alexander N. KROT  Mikhail I. PETAEV  Alexander A. ULYANOV  Klaus KEIL  Masamichi MIYAMOTO 《Meteoritics & planetary science》2001,36(5):629-641

Abstract— Amoeboid olivine aggregates (AOAs) from the reduced CV chondrites Efremovka, Leoville and Vigarano are irregularly‐shaped objects, up to 5 mm in size, composed of forsteritic olivine (Fa_<10) and a refractory, Ca, Al‐rich component. The AOAs are depleted in moderately volatile elements (Mn, Cr, Na, K), Fe, Ni‐metal and sulfides and contain no low‐Ca pyroxene. The refractory component consists of fine‐grained calcium‐aluminum‐rich inclusions (CAIs) composed of Al‐diopside, anorthite (An₁₀₀), and magnesium‐rich spinel (～1 wt% FeO) or fine‐grained intergrowths of these minerals; secondary nepheline and sodalite are very minor. This indicates that AOAs from the reduced CV chondrites are more pristine than those from the oxidized CV chondrites Allende and Mokoia. Although AOAs from the reduced CV chondrites show evidence for high‐temperature nebular annealing (e.g., forsterite grain boundaries form 120° triple junctions) and possibly a minor degree of melting of Al‐diopside‐anorthite materials, none of the AOAs studied appear to have experienced extensive (>50%) melting. We infer that AOAs are aggregates of high‐temperature nebular condensates, which formed in CAI‐forming regions, and that they were absent from chondrule‐forming regions at the time of chondrule formation. The absence of low‐Ca pyroxene and depletion in moderately volatile elements (Mn, Cr, Na, K) suggest that AOAs were either removed from CAI‐forming regions prior to condensation of these elements and low‐Ca pyroxene or gas‐solid condensation of low‐Ca‐pyroxene was kinetically inhibited.  相似文献   

Theoretical interpretation of cosmic magnetic fields     

F. I. Mikhail  M. I. Wanas  A. M. Eid 《Astrophysics and Space Science》1995,228(1-2):221-237

The paper discusses the possibilty of interpreting the magnetic fields of astronomical bodies in the framework of a unified field theory.Using one of the solutions of the generalized field theory, a direct relation between the polar magnetic field, the angular velocity and the gravitational potential of the body considered, is obtained. The geometric model used for applications has spherical symmetry and is of the type (FIGI).The predictions of the theoretical formula, obtained from the model, are compared with available observational data, and with the empirical formula of Blackett. The theoretical formula gives a possible interpretation of a seed magnetic field which will develop and produce the large-scale magnetic field observed for celestial objects. The formula shows that the field is generated as a result of rotation of a massive object.  相似文献   

Polarization characteristics of Jensch coelostat     

Mikhail L. Demidov 《Solar physics》1991,135(1):193-197

The polarization characteristics of the Jensch coelostat, used at the Sayan observatory, are presented. Results of calculations of the instrumental polarization (IP) are compared with the observations. It is shown that structural features of the Jensch coelostat lead to a very important dependence of the Stokes's parameters, that characterize the IP, on solar coordinates.  相似文献   

Night Sky Brightness and Colour at Different Zenith Distances at Abu-Simbel Site     

S. Nawar  A.B. Morcos  J.S. Mikhail 《Astrophysics and Space Science》1998,262(4):485-496

Photoelectric observations of night sky brightness at different zenith distances in blue, yellow and red colours have been carried out at Abu-Simbel site. Variations in the night sky brightness and (B-V) colour index with time are detected. These variations have been explained by the change of the galactic latitude of the observed point with time. The deduced results of night sky brightness have been compared with that obtained before at other sites. It has been found for both blue and yellow colours, that Abu-Simbel is the darkest site especially for zenith distances equal or greater than 60°. The present values of night sky brightness and colour have been obtained for the first time at Abu-Simbel site. The average night sky brightness at the galactic plane is 22.58 mag/arc sec² for blue and 21.66 mag/arc sec² for yellow. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

High-Performance Parallel Solver for Integral Equations of Electromagnetics Based on Galerkin Method     

Mikhail Kruglyakov  Lidia Bloshanskaya 《Mathematical Geosciences》2017,49(6):751-776

A new parallel solver for the volumetric integral equations (IE) of electrodynamics is presented. The solver is based on the Galerkin method, which ensures convergent numerical solution. The main features include: (i) memory usage eight times lower compared with analogous IE-based algorithms, without additional restrictions on the background media; (ii) accurate and stable method to compute matrix coefficients corresponding to the IE; and (iii) high degree of parallelism. The solver’s computational efficiency is demonstrated on a problem of magnetotelluric sounding of media with large conductivity contrast, revealing good agreement with results obtained using the second-order finite-element method. Due to the effective approach to parallelization and distributed data storage, the program exhibits perfect scalability on different hardware platforms.  相似文献   

The Arctic Coastal Dynamics Database: A New Classification Scheme and Statistics on Arctic Permafrost Coastlines     

Hugues Lantuit  Pier Paul Overduin  Nicole Couture  Sebastian Wetterich  Felix Aré  David Atkinson  Jerry Brown  Georgy Cherkashov  Dmitry Drozdov  Donald Lawrence Forbes  Allison Graves-Gaylord  Mikhail Grigoriev  Hans-Wolfgang Hubberten  James Jordan  Torre Jorgenson  Rune Strand ?deg?rd  Stanislav Ogorodov  Wayne H. Pollard  Volker Rachold  Sergey Sedenko  Steve Solomon  Frits Steenhuisen  Irina Streletskaya  Alexander Vasiliev 《Estuaries and Coasts》2012,35(2):383-400

Arctic permafrost coasts are sensitive to changing climate. The lengthening open water season and the increasing open water area are likely to induce greater erosion and threaten community and industry infrastructure as well as dramatically change nutrient pathways in the near-shore zone. The shallow, mediterranean Arctic Ocean is likely to be strongly affected by changes in currently poorly observed arctic coastal dynamics. We present a geomorphological classification scheme for the arctic coast, with 101,447?km of coastline in 1,315 segments. The average rate of erosion for the arctic coast is 0.5?m? year^?1 with high local and regional variability. Highest rates are observed in the Laptev, East Siberian, and Beaufort Seas. Strong spatial variability in associated database bluff height, ground carbon and ice content, and coastline movement highlights the need to estimate the relative importance of shifting coastal fluxes to the Arctic Ocean at multiple spatial scales.  相似文献