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941.
Lunar gravity field determination using SELENE same-beam differential VLBI tracking data 总被引:2,自引:0,他引:2
S. Goossens K. Matsumoto Q. Liu F. Kikuchi K. Sato H. Hanada Y. Ishihara H. Noda N. Kawano N. Namiki T. Iwata F. G. Lemoine D. D. Rowlands Y. Harada M. Chen 《Journal of Geodesy》2011,85(4):205-228
A lunar gravity field model up to degree and order 100 in spherical harmonics, named SGM100i, has been determined from SELENE and historical tracking data, with an emphasis on using same-beam S-band differential VLBI data obtained in the SELENE mission between January 2008 and February 2009. Orbit consistency throughout the entire mission period of SELENE as determined from orbit overlaps for the two sub-satellites of SELENE involved in the VLBI tracking improved consistently from several hundreds of metres to several tens of metres by including differential VLBI data. Through orbits that are better determined, the gravity field model is also improved by including these data. Orbit determination performance for the new model shows improvements over earlier 100th degree and order models, especially for edge-on orbits over the deep far side. Lunar Prospector orbit determination shows an improvement of orbit consistency from 1-day predictions for 2-day arcs of 6 m in a total sense, with most improvement in the along and cross-track directions. Data fit for the types and satellites involved is also improved. Formal errors for the lower degrees are smaller, and the new model also shows increased correlations with topography over the far side. The estimated value for the lunar GM for this model equals 4902.80080±0.0009 km3/s2 (10 sigma). The lunar degree 2 potential Love number k 2 was also estimated, and has a value of 0.0255 ± 0.0016 (10 sigma as well). 相似文献
942.
The day-to-day variations in ozone content at Uccle (51oN) during some stratospheric warming events are ex-amined. In particular, the attention is focused on the timing of commencement of ozone enhancement prior to peak day of warming and on the relationship in the ozone content between the upper and lower stratosphere. These two features are compared with the predictions of ozone transport models. There seems to be an agreement between mod-el predictions and observed features in some cases. 相似文献
943.
944.
Metamorphic history of the South Tibetan Detachment System,Mt. Everest region,revealed by RSCM thermometry and phase equilibria modelling 总被引:2,自引:0,他引:2
J. M. COTTLE D. J. WATERS O. BEYSSAC M. J. JESSUP 《Journal of Metamorphic Geology》2011,29(5):561-582
This study combines microstructural observations with Raman spectroscopy on carbonaceous material (RSCM), phase equilibria modelling and U–Pb dating of titanite to delineate the metamorphic history of a well‐exposed section through the South Tibetan Detachment System (STDS) in the Dzakaa Chu valley of Southern Tibet. In the hanging wall of the STDS, undeformed Tibetan Sedimentary Series rocks consistently record peak metamorphic temperatures of ~340 °C. Temperatures increase down‐section, reaching ~650 °C at the base of the shear zone, defining an apparent metamorphic field gradient of ~310 °C km?1 across the entire structure. U–Th–Pb geochronological data indicate that metamorphism and deformation at high temperatures occurred over a protracted period from at least 20 to 13 Ma. Deformation within this 1‐km‐thick zone of distributed top‐down‐to‐the‐northeast ductile shear included a strong component of vertical shortening and was responsible for significant condensing of palaeo‐isotherms along the upper margin of the Greater Himalayan Series (GHS). We interpret the preservation of such a high metamorphic gradient to be the result of a progressive up‐section migration in the locus of deformation within the zone. This segment of the STDS provides a detailed thermal and kinematic record of the exhumation of footwall GHS rocks from beneath the southern margin of the Tibetan plateau. 相似文献
945.
Sai S.W. Latt 《Singapore journal of tropical geography》2013,34(1):40-56
One major aim of the Greater Mekong Subregion (GMS) integration programme, supported by the Asian Development Bank (ADB), is to foster regional ‘community’ for sharing resources, people and financial flows. This ‘community’ is the target of both economic growth and poverty reduction. The emphasis on ‘community’ in the ADB's mushrooming quantity of documents raises important questions about what kinds of people are included, in what roles and with what kinds of support and protection. This paper explores these questions in relation to the political economy of regulating ethnic migrants from Myanmar working in Thailand. This paper argues that extra‐legal relations between migrants and state/para‐state agents constitute a crucial part of regulation. In transferring the regulation of migration to the national scale, the ADB inadvertently reinforces national differences between Thais and cross‐border people. Additionally, the complicated and fluctuating implementation of national regulations in both countries leaves migrants subject to violence and extortion from state and quasi‐state agents in Thailand. This paper shows that the dynamics of global capitalism require ‘deportable labour’ supplied by ethnic migrants who are included in the GMS community as the most invisible, vulnerable and exploited members. 相似文献
946.
Intensive experimental as well as numerical investigations have been carried out in order to develop empirical relationships to predict wetting front travel time and infiltration rate in deep arid region alluvium due to the effect of variable rainfall intensity and ponding head, respectively. A rainfall simulator that is capable of producing variable rainfall intensity up to 160 mm/h and a large diameter infiltrometer were constructed in the study area and then used to test the effect of rainfall and ponding head up to a depth of 3 m. Results of these experiments were utilized to calibrate an unsaturated zone model which was then used to test different scenarios for wetting front movement at depths beyond the scope of these experiments. Empirical infiltration relationships for rainfall and ponding head, respectively, were derived for shallow and deep soil columns from these experiments. 相似文献
947.
948.
Iodine contents of soils developed over the major rock formations of the northern zone of the Eastern Pontide Tectonic Belt
(Northeastern Turkey) have been investigated with respect to soil-parent rock relationship, effect of topography, elevation,
and climate to construe its effect on the health of the local population. Samples were collected from the A and B horizons
of the soils developed over the major stratigraphic units constituting the eastern Pontides, including the Lower Basic Complex
of Jurassic-Lower Cretaceous age, the Berdiga limestone (Jurassic-lower Cretaceous), the Dagbasi granitoid (Upper Cretaceous),
volcano-sedimentary sequence of Upper Cretaceous age, ore-bearing and barren dacites of Upper Cretaceous age, and Neogene
alkaline basalts. Chemical analyses of soil samples indicate significantly lower iodine abundances for all the soils studied
(5–28 ppm) in comparison to the average abundance of iodine in analogous soils of other parts of the world (22–93 ppm). The
concentration of iodine in soils developed over the same geologic formation decrease with increasing elevation. In certain
cases, this decrease may reach up to 70%. Goiter is highly common throughout this region in Turkey. The results of this study
suggest that the iodine deficiency of region’s soils may be a principal underlying cause for this area of Turkey being an
endemic goiter region. 相似文献
949.
950.