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51.
Floating tephra was deposited together with ice core,snow layer,abyssal sediment,lake sediments,and other geological records.It is of great significance to interpret the impact on the climate change of volcanic eruptions from these geological records.It is the first time that volcanic glass was discovered from the peat of Jinchuan(金川)Maar,Jilin(吉林)Province,China.And it is in situ sediments from a near-source explosive eruption according to particle size analysis and identification results.The tephra were neither from Tianchi(天池)volcano eruptions,Changbai(长白)Mountain,nor from Jinlongdingzi(金龙顶子)volcano about 1 600 aBP eruption,but maybe from an unknown eruption of Longgang(龙岗)volcano group according to their geochemistry and distribution.Geochemical characters of the tephra are similar to those of Jingiongdingzi,which are poor in s.Jica,deficient in alkali,Na20 content is more than K20 content,and are similar to distribution patterns of REE and incompatible elements,which helps to speculate that they originated from the same mantle magma with rare condemnation,and from basaltic explosive eruption of Longgang volcano group.The tephra,from peat with age proved that the eruption possibly happened in 15 BC-26 AD,is one of Longgang volcano group eruption that was not recorded and is earlier than that of Jinglongdingzi about 1 600 aBP eruption.And the sedimentary time of tephra is during the period of low temperature alteration.which may be the influence of eruption toward the local climate according to the correlativity of eruption to local temperature curve of peat cellulose oxygen isotope. 相似文献
52.
K. S. Rao Y. S. Rao H. K. Al Jassar 《Journal of the Indian Society of Remote Sensing》2008,36(2):123-136
Spaceborne Imaging Radar (SIR-C) data acquired over Gujarat, India in 1994 were processed and analysed using differnet techniques
applicable to polarimetric SAR data such as polarization signatures, polarization index, decomposition of the signal and polarization
phase difference and limited groundtruth data. It has been observed that multi-frequency polarimetric data enhances the potential
of retrieving geo-physical parameters. The polarization signatures are found to vary with the nature of the target. Target
decomposition of the returned signal will be useful for the classification of various features. Polarization Phase Difference
(PPD) gives good information about the vegetation parameters. 相似文献
53.
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55.
Lars E. Sjöberg 《Journal of Geodesy》2008,82(9):565-567
Through each of two known points on the ellipsoid a geodesic is passing in a known azimuth. We solve the problem of intersection
of the two geodesics. The solution for the latitude is obtained as a closed formula for the sphere plus a small correction,
of the order of the eccentricity of the ellipsoid, which is determined by numerical integration. The solution is iterative.
Once the latitude is obtained, the longitude is determined without iteration. 相似文献
56.
This paper introduces a new method for GPS signal acquisition, which is based on the repeatability of successive code phase
measurements and the M-of-N search algorithm. The performance of the proposed method in terms of probability of signal detection
is similar to that of traditional methods, except that the calculation of the probability of detection does not rely on the
noise distribution or the Carrier-to-Noise ratio (C/N0). The code phase repeatability-based method is presented along with equations for probability of detection and probability
of false detection. If the distribution of the noise is known, it also provides an estimate of the C/N0. The proposed method is illustrated for coherent and non-coherent acquisition and C/N0 estimation. 相似文献
57.
This paper presents a continuous version of the model of distribution dynamics to analyse the transition dynamics and implied
long-run behaviour of the EU-27 NUTS-2 regions over the period 1995–2003. It departs from previous research in two respects:
first, by introducing kernel estimation and three-dimensional stacked conditional density plots as well as highest density regions
plots for the visualisation of the transition function, based on Hyndman et al. (J Comput Graph Stat 5(4):315–336, 1996), and second, by combining Getis’ spatial filtering view with kernel estimation to explicitly account for the spatial dimension of the
growth process. The results of the analysis indicate a very slow catching-up of the poorest regions with the richer ones,
a process of shifting away of a small group of very rich regions, and highlight the importance of geography in understanding
regional income distribution dynamics.
相似文献
Manfred M. FischerEmail: |
58.
59.
Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin 总被引:1,自引:1,他引:0
Hans-Jürgen Gawlick Wolfgang Frisch Lirim Hoxha Paulian Dumitrica Leopold Krystyn Richard Lein Sigrid Missoni Felix Schlagintweit 《International Journal of Earth Sciences》2008,97(4):865-881
The Mirdita Ophiolite Zone in Albania is associated with widespread mélanges containing components of up to nappe-size. We
dated matrix and components of the mélange by radiolarians, conodonts, and other taxa. The components consist of radiolarites,
pelagic limestones and shallow-water limestones, all of Triassic age, as well as ophiolites. Triassic radiolarite as a primary
cover of ophiolite material proves Middle Triassic onset of Mirdita ocean-floor formation. The mélange contains a turbiditic
radiolarite-rich matrix (“radiolaritic flysch”), dated as Late Bajocian to Early Oxfordian. It formed as a synorogenic sediment
during west-directed thrusting of ophiolite and sediment-cover nappes representing ocean floor and underplated fragments of
the western continental margin. The tectonic structures formed during these orogenic events (“Younger Kimmeridian or Eohellenic
Orogeny”) are sealed by Late Jurassic platform carbonates. The geological history conforms with that of the Inner Dinarides
and adjoining areas; we therefore correlate the Mirdita-Pindos Ophiolite Zone with the Vardar Zone and explain its present
position by far-distance west-directed thrusting. 相似文献
60.
We developed light requirements for eelgrass in the Pacific Northwest, USA, to evaluate the effects of short- and long-term
reductions in irradiance reaching eelgrass, especially related to turbidity and overwater structures. Photosynthesis-irradiance
experiments and depth distribution field studies indicated that eelgrass productivity was maximum at a photosynthetic photon
flux density (PPFD) of about 350–550 μmol quanta m−2 s−1. Winter plants had approximately threefold greater net apparent primary productivity rate at the same irradiance as summer
plants. Growth studies using artificial shading as well as field monitoring of light and eelgrass growth indicated that long-term
survival required at least 3 mol quanta m−2 day−1 on average during spring and summer (i.e., May-September), and that growth was saturated above about 7 mol quanta m−2 day−1. We conclude that non-light-limited growth of eelgrass in the Pacific Northwest requires an average of at least 7 mol quanta
m−2 day−1 during spring and summer and that long-term survival requires a minimum average of 3 mol quanta m−2 day−1. 相似文献