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1.
Using observations obtained with the Clark Lake radioheliograph we determined the diameter of the Sun in the decameter wavelength range. Both equatorial and polar diameters increase with decreasing frequency, as D=Af
. The eccentricity of the brightness distribution appears to remain constant in the frequency range (30–74 MHz) in good agreement with the optical results in a corresponding height range. The smaller size of the polar diameter is attributed to coronal holes covering the poles during the period of our observations, while streamers were observed at the equator most of the time. 相似文献
2.
Microstructural observations on natural syntectonic fibrous veins: implications for the growth process 总被引：3，自引：0，他引：3
Syntectonic antitaxial and ataxial fibrous veins were investigated using SEM, microprobe, cathodoluminescence (CL) and optical microscopy. In antitaxial calcite veins, fibres and surrounding selvage grew simultaneously, with similar growth rates of crystallographically differently oriented grains. New material precipitated at the vein margin in antitaxial and bi-mineralic ataxial microstructures. Bridges of country rock material formed during vein growth in an initial en-echelon vein system. In our antitaxial and bi-mineralic ataxial samples, the spacing of solid inclusions does not reflect individual crack-seal openings. 相似文献
3.
Comparison of maps of the Sun obtained over the period June 29 to July 8, 1982 at 169 MHz with the Nançay Radioheliograph and at 73.8, 50, and 30.9 MHz with the Clark Lake Radioheliograph shows that the slowly varying component at meter and decameter wavelengths is not always thermal emission. During the period under study weak noise storm continua were the most frequent sources of slowly varying component at 169 and 73.8 MHz. Most filaments show no radio counterpart on the disk. A streamer has been detected on the disk from 169 to 30.9 MHz with an optimum observability at 50 MHz. The brightest source of the slowly varying component from 73.8 to 30.9 MHz for most of the period was located above an extended coronal hole in a region where a depression was observed at 169 MHz. In favorable cases, electron densities can be derived from the positions of noise storms and radio streamers; these are in agreement with previous K-corona eclipse observations. 相似文献
4.
The new TeePee Tee array of the Clark Lake Radio Observatory has been used to observe the quiet Sun at 121.5, 73.8 and 26.3 MHz. The equatorial brightness distributions at all three frequencies, and the polar brightness distributions at the two higher ones have been measured. From the observed total fluxes and half-power diameters we have derived the peak brightness temperatures of the solar disk as well as of some sources of the slowly varying component.On leave of absence from Instituto Argentino de Radioastronomía, Argentina. 相似文献
5.
General purpose Computational Fluid Dynamics (CFD) solvers are frequently used in small-scale urban pollution dispersion simulations
without a large extent of ver- tical flow. Vertical flow, however, plays an important role in the formation of local breezes,
such as urban heat island induced breezes that have great significance in the ventilation of large cities. The effects of
atmospheric stratification, anelasticity and Coriolis force must be taken into account in such simulations. We introduce a
general method for adapting pressure based CFD solvers to atmospheric flow simulations in order to take advantage of their
high flexibility in geometrical modelling and meshing. Compressibility and thermal stratification effects are taken into account
by utilizing a novel system of transformations of the field variables and by adding consequential source terms to the model
equations of incompressible flow. Phenomena involving mesoscale to microscale coupled effects can be analyzed without model
nesting, applying only local grid refinement of an arbitrary level. Elements of the method are validated against an analytical
solution, results of a reference calculation, and a laboratory scale urban heat island circulation experiment. The new approach
can be applied with benefits to several areas of application. Inclusion of the moisture transport phenomena and the surface
energy balance are important further steps towards the practical application of the method. 相似文献
6.
The aim of this study is to recognize the basic clastic rock types on the basis of Hounsfield Units (HUs) by using statistical methods (hypothesis tests, distribution fitting, and confidence intervals). How does this recognition depend on depositional history of samples tested? Does the numerical pattern of HUs obtained from small-scale analyzing of some particular sedimentary structures coincide to the textural expectations of those sedimentary structures? Are the HU values provided by the CT measurements capable of evidencing micro-cycles belonging to a particular depositional history?For testing the numerical recognition, we analyze macroscopically homogeneous argillaceous marl, siltstone and fine sandstone samples with similar depositional background, age, and degree of diagenesis. The preliminary research shows that the Hounsfield Units can identify different sedimentary rocks considerably well. There are significant differences among the confidence intervals belonging to the different rock types. However, there also have been some slight overlaps among them.For analyzing the effects of the depositional processes in case of a particular rock type, samples from channel sandstone, distributary mouth-bar, massive (structureless) sandstone from a delta-fed turbidity fan, and channel sandstone with traction carpet origin from a delta-fed turbidity fan (all coming from Pannonian basin filling series) are used. The results prove again the significant differences in the terms of both confidence intervals and distribution-types; however, some overlapping also occurs. 相似文献
7.
Robyn Pickering Jan D. Kramers Tim Partridge Janos Kodolanyi Thomas Pettke 《Quaternary Geochronology》2010,5(5):544-558
Speleothems are found in association with hominin fossil-bearing cave deposits in South Africa and can be used to provide valuable chronological constraints. Such material is generally too old for U–Th dating and, although U–Pb geochronology presents a suitable alternative, bulk U concentrations are typically too low (<0.05 μg/g) to provide useful ages. For this reason, we used a simple non-invasive beta-scanner imaging screening step to identify U-rich (≥1 μg/g) domains that could be analyzed with MC-ICP-MS techniques to provide U–Pb ages. We demonstrate the technique using samples from Sterkfontein cave that exhibit infrequent <1 cm-thick layers with U concentrations ≥1 μg/g. Relict aragonite needles are found exclusively in these U-rich layers. We analyzed material from the same flowstone suite as Walker et al. (2006) and obtained a U–Pb age of ～2.3 Ma that agrees well with their estimate of 2.24 ± 0.09 Ma. We also obtained similar U–Pb (0.164 ± 0.026 to 0.200 ± 0.052 Ma) and U–Th (0.148 ± 0.003 Ma) ages for another sample exhibiting U-rich layers. We recognize that open-system behaviour during the partial transformation of aragonite to calcite is a potential problem and argue, on the basis of geochemistry and age consistencies, that recrystallization took place rapidly after speleothem formation and did not significantly affect the U–Pb ages. 相似文献
8.
Matyasovszky István Makra László Tusnády Gábor Csépe Zoltán Nyúl László G. Chapman Daniel S. Sümeghy Zoltán Szűcs Gábor Páldy Anna Magyar Donát Mányoki Gergely Erostyák János Bodnár Károly Bergmann Karl-Christian Deák Áron József Thibaudon Michel Albertini Roberto Bonini Maira Šikoparija Branko Radišić Predrag Gehrig Regula Rybníček Ondřej Severova Elena Rodinkova Victoria Prikhodko Alexander Maleeva Anna Stjepanović Barbara Ianovici Nicoleta Berger Uwe Seliger Andreja Kofol Weryszko-Chmielewska Elżbieta Šaulienė Ingrida Shalaboda Valentina Yankova Raina Peternel Renata Ščevková Jana Bullock James M. 《Theoretical and Applied Climatology》2018,133(1-2):277-295
Theoretical and Applied Climatology - The drivers of spatial variation in ragweed pollen concentrations, contributing to severe allergic rhinitis and asthma, are poorly quantified. We analysed the... 相似文献
9.
Joyce Schmatz Marc Holland Steffen Giese Wouter van der Zee Janos. L. Urai 《Journal of the Geological Society of India》2010,75(1):74-88
The aim of this study is to improve our knowledge of the processes that lead to clay smear during faulting of a layered sand-clay
sequence in an analogue sandbox model. We carefully characterized mechanical properties of the materials used by a series
of geotechnical tests. Displacement field was quantified using PIV (Particle Image Velocimetry). The model is water-saturated
to allow the deformation of wet clay and sand in one experiment comprising a sand package with a horizontal layer of clay
above a predefined rigid basement fault. The thickness and rigidity of the clay layer are the parameters varied in this study.
The model shows a range of structures that are related to competence contrast between sand and different clay types. Results
show ductile shearing of soft clay with a transition to brittle fracturing of stiff clay accompanied by the formation of rotating
clay blocks in the fault zone. Localized deformation is observed through time showing (i) the propagation of one active fault
migrating laterally through the sediment package, and (ii) the formation of a stable prism between two or more active faults
that gets progressively smaller with minor rotation of the hanging wall fault. Continuous clay smear is observed resulting
from the lateral injection of clay as well as from a reworked mixture of sand and clay. 相似文献
10.
Observations of a coronal disturbance on 1973 January 11 commencing at 18h01m UT are described. The event is homologous with an earlier disturbance from the same region of the corona. The observations suggest that a cloud of coronal gas containing 4 × 1039 electrons propagated outwards to 5 R
behind a piston-driven shock wave travelling at a velocity of 800 to 1200 km s–1.On leave from Division of Radiophysics, CSIRO, Sydney, Australia. 相似文献