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41.
Superstructures in synthetic mullite, Al4+2x Si2?2x O10?x , prepared using the zone melting technique, are studied by high resolution electron microscopy (HREM), electron diffraction, and in situ energy dispersive X-ray spectroscopy. For x=0.40 composition HREM images indicate only short-range order. Near x=0.5 composition mullite has an antiphase domain structure with antiphase boundaries (APB's) oriented parallel to (100). For higher Al-content the APB's run in non-rational orientations which are slightly inclined against the {601}-planes. We propose models for the superstructures in which oxygen vacancies are arranged in channels parallel to the crystal b-axis. The models are supported by a one-to-one match between observed and computer-simulated images. An Al-rich limit of x=2/3 for mullite is deduced on the basis of stereochemical considerations. Different ordering schemes for the tetrahedral cations are believed to result in the orientation change of the APB's near x=0.5 composition. 相似文献
42.
M.A. Gasiński 《Cretaceous Research》1983,4(3):221-249
Eighteen Albian and Cenomanian planktic Foraminiferida from the Pieniny Klippen Belt of Poland are discussed. A local biostratigraphic zonation (six zones) is proposed and certain problems of palaeoecology are reviewed. The lithostratigraphical element is the so-called Trawne Beds, a Cretaceous flysch in the Pieniny Klippen Belt. 相似文献
43.
N. N. Bursov Yu. N. Pariĭskiĭ E. K. Maĭorova M. G. Mingaliev A. B. Berlin N. A. Nizhel’skiĭ I. A. Glushkova T. A. Semenova 《Astronomy Reports》2007,51(3):197-214
A catalog of radio sources detected in a deep RATAN-600 survey is presented. The catalog was obtained in the region 0h ≤ RA2000.0 ≤ 24h, Dec2000.0 = 41°30′42″ ± 2′, at the declination of the bright radio source 3C 84. There were nine sessions of multi-wavelength observations at wavelengths λ = 1–55 cm, and more than 300 daily scans were accumulated at each wavelength. This is the first stage in the reduction of an extensive database accumulated by the Cosmological Gene Project. The RATAN-600 Zenith Field (RZF) catalog was obtained at the central wavelength of 7.6 cm, and contains 437 radio sources, virtually all of which have been identified with NVSS objects. Most of the flux densities for the catalog sources are above the 5σ level. Noise from faint (mainly new) background sources at a level of about 0.8 mJy has been detected. The minimum flux density of the catalog, 2.5 mJy, is comparable to the flux-density linit of the NVSS catalog. The catalog is more than 80% complete for sources with flux densities >3 mJy. 相似文献
44.
We consider the advantages of a formalism based on concept of the asymmetric continuum and we present some equivalence theorems
relating it to the asymmetric elasticity and to micropolar and micromorphic theories as founded by Nowacki, Cosserats and
Eringen.
We consider the basic processes in an asymmetric continuum which could be reduced to the point basic motions/deformations.
The co-action of spin and shear motions is assumed to play the main role in fracturing process, while the constitutive relation
between the antisymmetric stresses and rotations replaces the friction constitutive law. 相似文献
45.
46.
Measurements of topsoil magnetic susceptibility are often used for quick assessment of soil contamination of anthropogenic
origin, with heavy metals or other pollutants. However, because of complicated correlations between low-field magnetic susceptibility
(shortened to magnetic susceptibility) of topsoil and soil pollution, the outcome of a field magnetometry survey can not be
related directly to soil pollution. For each case study, the results should be interpreted on their own taking into account
not only the type of pollution but also pedogenic, biogenic and environmental factors. In practice, it is very difficult to
measure and consider all these factors. Here we illustrate the merit of geostatistical methods, which are focused on the spatial
variability of a phenomenon, in the interpretation of soil magnetometry results.
This article presents the analysis of spatial variability of top soil layers magnetic susceptibility-within the Upper Silesia
Industrial Region (USIR)-using semivariance analysis. It also explains how to adjust the sampling density of field magnetometry
measurements to spatial variability of the soil pollution as well as to the spatial scale of the investigated area. For this
purpose, the values of magnetic susceptibility have been measured by using various sampling densities at areas of different
size located within USIR. This enabled to determine the main scales of magnetic susceptibility spatial variability of soils
within USIR using semivariance. A few distinct scales of variability were found from the site scale to a more regional scale.
Variability ranges of 30 km, 12 km, and 5 km refer to the large regional scale, whereas smaller ranges of few hundreds down
to a few tens of meters, can be attributed to the local (site) scale. In addition, the precision of the measuring campaigns,
performed within USIR with different sampling densities, was compared through the analysis of the spatial variability of the
soil magnetic susceptibility signal by using ordinary kriging.
jarek97@yahoo.com, piotr.fabijanczyk@is.pw.edu.pl 相似文献
47.
48.
Alfred Kepiński 《Aquatic Sciences - Research Across Boundaries》1962,24(2):272-290
Ohne Zusammenfassung 相似文献
49.
50.
Summary Two groups of basaltic rocks with normal and reversed NRM were examined. It was found that in both groups the primary NRM, synchronous with the period of rock formation, is preserved. Relations of the primary NRM to the origin and the degree of oxidation of magnetic minerals were considered in detail. 相似文献