排序方式: 共有22条查询结果,搜索用时 15 毫秒
1.
Avanesov G Zhukov B Ziman YA Kostenko V Kuzmin A Murav'ev V Fedotov V Bonev B Mishev D Petkov D Krumov A Simeonov S Boycheva V Uzunov YU Weide GG Halmann D Pössel W Head J Murchie S Schkuratov YuG Berghänel R Danz M Mangoldt T Pihan U Smith B 《Planetary and Space Science》1991,39(1-2):281-295
From February to March 1989 the Phobos 2 spacecraft took 37 TV images of Phobos at a distance of 190-1100 km. These images complement Mariner-9 and Viking data by providing higher-resolution coverage of a large region West of the crater Stickney (40-160 degrees W) and by providing disk-resolved measurements of surface brightness at a greater range of wavelengths and additional phase angles. These images have supported updated mapping and characterization of large craters and grooves, and have provided additional observations of craters' and grooves' bright rims. Variations in surface visible/near-infrared color ratio of almost a factor of 2 have been recognized; these variations appear to be associated with the ejecta of specific large impact craters. Updated determinations of satellite mass and volume allow calculation of a more accurate value of bulk density, 1.90 +/- 0.1 g cm-3. This is significantly lower than the density of meteoritic analogs to Phobos' surface, suggesting a porous interior perhaps containing interstitial ice. 相似文献
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Adam Tomaových Ivo Gallmetzer Alexandra Haselmair Darrell S. Kaufman Borut Mavri
Martin Zuschin 《Sedimentology》2019,66(3):781-807
Carbonate sediments in non‐vegetated habitats on the north‐east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarce; and (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand‐dwelling Gouldia minima and opportunistic Corbula gibba are time‐averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co‐occurring Gouldia minima. This age difference is driven by temporally disjunct production of two species coupled with decimetre‐scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top‐core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft‐bottom vegetated zones and hard‐bottom Arca beds) and present‐day oligophotic communities with organic‐loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats. 相似文献
4.
In this report, we present the situation in Slovenia, Europe with regard to natural hazards, emphasizing land-sliding problems.
Furthermore, we shortly present the University of Ljubljana and the Faculty of Civil and Geodetic Engineering as the new member
of the ICL that was selected to be the World Center of Excellence on Landslide Risk Reduction for the period of 2008–2013
with the project entitled “Mechanisms of landslides in over-consolidated clays and flysch” in the Activity scale and targeted
region as “National.” Some preliminary results of this project are shortly presented at the end. 相似文献
5.
Z. Petkovšek 《Meteorology and Atmospheric Physics》1992,47(2-4):237-245
Summary Problems of turbulent dissipation of a cold air lake (CAL) and the inversion layer bordering CAL on the upper boundary are presented and studied with the compound model. In wintertime such cold air lakes can persist for days even if rather strong winds are blowing above them. The required conditions for CAL dissipation are removed processes of its formation or maintenance, as well as a sufficiently strong invasion of turbulence in the inversion layer from above down-wards. By this, the inversion layer at first becomes stronger and dissipation is stopped, until the increase of turbulent kinetic energy of the upper flow enables further dissipation. Such turbulent dissipation process is shown by the model for typical conditions and for different initial values of the relevent variables.With 6 Figures 相似文献
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Radiative lifetimes for excited states in La ii, Ce ii, Pr ii, Nd ii, Sm ii, Yb i, Yb ii, and Lu ii have been determined by means of the beam-foil technique or the zero-field level-crossing method. The lifetimes for La, Ce, Pr, Nd, Sm, and Yb are shorter than those computed by summing the transition probabilities of Corliss and Bozman by a factor of up to ~5. The large discrepancies between the abundance of La, Ce, Pr, Nd, and Sm in the solar photosphere and in meteorites are eliminated or greatly reduced if the abundance determinations of the solar photosphere are based upon the gf values of Corliss and Bozman, corrected for by the present lifetimes. 相似文献
7.
Agriculture in Bulgaria entered a severe crisis in 1989 following the collapse of the central planning system. Since then it has been going through a transition towards market-based system and a structural transformation from large state cooperatives to smaller privately owned and operated farms and cooperatives. Irrigation, a major water use until recently, has been strongly affected by these processss, and has dropped to a point where less than 15% of the areas equipped for irrigation are actually irrigated. Heavy state investments in the irrigation subsector and its vital importance for the economy make it imperative to up-grade and restructure irrigated agriculture to reflect new forms of land ownership and farming, as well as the current and future organizational patterns of the 相似文献
8.
Cosmic rays and the electric field of thunderclouds: Evidence for acceleration of particles (runaway electrons) 总被引:1,自引:0,他引:1
We present the data on correlations of the intensity of the soft component of cosmic rays with the local electric field of the near-earth atmosphere during thunderstorm periods at the Baksan Valley (North Caucasus, 1700 m a.s.l.). The large-area array for studying the extensive air showers of cosmic rays is used as a particle detector. An electric field meter of the ‘electric mill’ type (rain-protected) is mounted on the roof of the building in the center of this array. The data were obtained in the summer seasons of 2000–2002. We observe strong enhancements of the soft component intensity before some lightning strokes. At the same time, the analysis of the regression curve ‘intensity versus field’ discovers a bump at the field sign that is opposite to the field sign corresponding to acceleration of electrons. It is interpreted as a signature of runaway electrons from the region of the strong field (with opposite sign) overhead. 相似文献
9.
The Stogovce landslide in SW Slovenia triggered during the September 2010 extreme rainfall event 总被引:4,自引:4,他引:0
Ana Petkov?ek Rok Fazarinc Marko Ko?evar Matej Ma?ek Bojan Majes Matja? Miko? 《Landslides》2011,8(4):499-506
From September 16 to September 20, 2010, a cold weather front went across Slovenia. A heavy 4-day rainfall totaling between
300 and 520 mm caused large floods and triggered numerous rainfall-induced landslides. The damage due to the floods and landslides
is estimated over 250 million Euros. One of the largest landslides covering the area of approximately 15 ha was triggered
on flysch bedrock, just below a limestone overthrust zone. The sliding material properties, the inclinations of the slope,
and the water catchment area indicate that the landslide may transform into a fast moving debris flow. The necessary protective
measures were taken to protect inhabitants and the infrastructure against the disaster. The Stogovce landslide is one of the
numerous rainfall-induced landslides that have occurred in Slovenia on flysch bedrock in the last 10 years. It proves that
landslide risk on flysch territory is increasing. Special program of monitoring and protective measures will have to be developed
in near future to protect densely populated areas against landslides as a consequence of weather extremes. 相似文献
10.
Routine monitoring of the quality status of water bodies demands the best cost‐benefit relation and sample‐size reduction is therefore welcomed. However, great caution is needed because such reduction affects the accuracy and variation of the results. In the present study we tested the influence of sample size (number of replicate samples) on reference condition values and within‐sample ecological quality ratio (EQR) variability of six commonly used ecological indices (taxa richness, Shannon–Wiener diversity, AMBI, Medocc index, Bentix and M‐AMBI). Analysis of soft‐bottom benthic invertebrate data from Slovenian coastal waters showed that sample size influenced the reference condition values of richness/diversity indices (taxa richness and Shannon–Wiener diversity) but not of the sensitivity/tolerance indices (AMBI, Medocc index, Bentix). Increased sample size decreased the within‐sample EQR variability and, concomitantly, increased the accuracy of site ecological status classification for all indices. The size of EQR variability differed depending on the index used. EQR variability of M‐AMBI, an index composed of metrics with different within‐sample EQR variability, was statistically the same as that of the metric with the lowest within‐sample EQR variability. Whether this is a common principle for multimetric indices remains to be confirmed. Based on these results, the use of at least three replicates is suggested to obtain reliable measures of reference condition and EQR for the assessment of ecological status. This level of replication is particularly necessary in areas with high diversity and environmental patchiness, and when richness/diversity measures and indices that include these measures are used. 相似文献