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51.
Patricia Bernárdez Ricardo Prego Santiago Giralt Jaume Esteve Miguel Caetano Santiago Parra Guillermo Francés 《Marine Geology》2012
A multidisciplinary study of the elemental geochemistry and mineralogical characteristics of the marine surficial sediment in the Northern Rias (NW Iberian Peninsula) has been carried out. The linkages between the marine sediment composition and their potential sources were examined.The influence of the river-borne sediments is only detected in the innermost part of the three Rias. Regional variations of the mineral assemblages are governed by the source-rock composition of the different geological complexes and the relative source-rock contribution controlled by the continental hydrology. Mineralogical composition of the Ortigueira Ria and adjacent shelf surficial sediments are mainly made up of mafic and ultramafic rocks of the Cape Ortegal complex indicated by the high content of Mg, Mn and chrysotile and riebeckite minerals. In areas nearby Ortegal complex the imprint of heavy minerals present in the surrounding rocks has also been recorded. Barqueiro and Viveiro Rias bed-sediments are influenced by granitic and metamorphic rocks from the Ollo de Sapo complex as revealed by the high contribution of muscovite and quartz.Mining activities in the continental domain left strong imprints on marine surficial sediments. Pyrite content is high in the innermost areas of the Ortigueira Ria since this mineral is exploited in the Mera River basin, whereas high muscovite percentages characterize the Viveiro Ria owing to the abundance of granitic rocks and its exploitation in the Landro River basin. Quartz content is high nearby Cape Estaca de Bares, induced by the presence of an important excavation of this material. 相似文献
52.
We study planar central configurations of the five-body problem where three of the bodies are collinear, forming an Euler
central configuration of the three-body problem, and the two other bodies together with the collinear configuration are in
the same plane. The problem considered here assumes certain symmetries. From the three bodies in the collinear configuration,
the two bodies at the extremities have equal masses and the third one is at the middle point between the two. The fourth and
fifth bodies are placed in a symmetric way: either with respect to the line containing the three bodies, or with respect to
the middle body in the collinear configuration, or with respect to the perpendicular bisector of the segment containing the
three bodies. The possible stacked five-body central configurations satisfying these types of symmetries are: a rhombus with
four masses at the vertices and a fifth mass in the center, and a trapezoid with four masses at the vertices and a fifth mass
at the midpoint of one of the parallel sides. 相似文献
53.
We prove the following weakened version of Poincaré's conjecture on the density of periodic orbits of the restricted three-body problem: The measure of Lebesgue of the set of bounded orbits which are not contained in the closure of the set of periodic orbits goes to zero when the mass parameter does. 相似文献
54.
55.
Line-transect data from sighting surveys conducted in the western Mediterranean (in 1991) and the Alboran Sea (in 1992) were analysed to estimate densities and numbers of striped and common dolphins in various areas of the western Mediterranean. Density of striped dolphins in the northwestern Mediterranean was estimated as 0.20 dolphins km−2 (CV = 0.24; 95% CI = 0.12 and 0.32) and was 41% higher than in the southwestern Mediterranean, where it was estimated as 0.12 dolphins km−2 (CV = 0.38; 95% CI = 0.05 and 0.25). The highest densities were observed in the Liguro–Provençal basin, with 0.24 dolphins km−2 (CV = 0.26; 95% CI = 0.14 and 0.40), and the Alboran Sea, with 0.20 dolphins km−2 (CV = 0.33; 95% CI = 0.10 and 0.36). These areas, and especially the Ligurian Sea, appear to be the most productive in terms of the food consumed by striped dolphins. Common dolphins were abundant only in the Alboran Sea with an estimated density of 0.16 dolphins km−2 (CV = 0.40; 95% CI = 0.08 and 0.35), scarce in the south Balearic area and almost absent in the northwestern Mediterranean. The magnitude of the dolphin by-catch in fishing operations in the Alboran Sea and other areas stresses the need for further assessment of densities and numbers, notably in the Alboran Sea and the North African Mediterranean waters. 相似文献
56.
GNSS data management and processing with the GPSTk 总被引:2,自引:0,他引:2
Dagoberto Salazar Manuel Hernandez-Pajares Jose M. Juan Jaume Sanz 《GPS Solutions》2010,14(3):293-299
We organize complex problems in simple ways using a GNSS data management strategy based on “GNSS Data Structures” (GDS), coupled
with the open source “GPS Toolkit” (GPSTk) suite. The code resulting from using the GDS and their associated “processing paradigm”
is remarkably compact and easy to follow, yielding better code maintainability. Furthermore, the data abstraction allows flexible
handling of concepts beyond mere data encapsulation, including programmable general solvers. An existing GPSTk class can be
modified to achieve the goal. We briefly describe the “GDS paradigm” and show how the different GNSS data processing “objects”
may be combined in a flexible way to develop data processing strategies such as Precise Point Positioning (PPP) and network-based
PPP that computes satellite clock offsets on-the-fly. 相似文献
57.
A method for obtaining the galvanic distortion matrix is presented so that the regional impedance tensor (free of distortion) is recovered. The method is a constrained stochastic heuristic method, which consists in randomly exploring the space of the distortion parameters. Constraints are imposed on the shortest periods of the regional impedance tensor that, at these short periods, tends to be two dimensional (or one dimensional). Depending on the constraints used, two different methods to recover the regional impedance tensor in this 2D/3D case are presented. Method 1 needs to find the strike of the short periods and Method 2 applies to the measurement directions. Twist, shear and anisotropy parameters are obtained. Thus, the regional impedance tensor is recovered with the only exception being the vertical shift due to the gain, which is equal for all the components of the tensor. Examples with synthetic impedance tensors from 2D/3D models perturbed with galvanic distortion are presented to illustrate how the algorithm works. The presence of noise in data is considered and rules for proceeding are provided. The same examples perturbed by Gaussian noise together with experimental data illustrate the capabilities of the algorithm. 相似文献
58.
We study a symmetric collinear restricted 3-body problem, where the equal mass primaries perform elliptic collisions, while
a third massless body moves in the line between the primaries, during the time between two consecutive elliptic collisions.
After desingularizing binary and triple collisions, we prove the existence of a transversal heteroclinic orbit beginning and
ending in triple collision. This orbit is the unique homothetic orbit that the problem possess. Finally, we describe the topology
of the compact extended phase space.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
59.
Jaume Bech Magali Suarez Ferran Reverter Pedro Tume Pedro Sánchez Joan Bech Alejandro Lansac 《Journal of Geochemical Exploration》2010
Selenium is an essential trace element in regard to human and other animals' health, but it presents a narrow range of dietary deficiency and toxic excess. Some phosphate rocks are rich in selenium. Furthermore it is necessary to control selenium's and other trace elements’ compositions in the phosphate rocks, because phosphorite ores of different geographical sites are varied, and even ores from the same outcrop can vary substantially in trace element levels. 相似文献
60.
In this paper we show the existence of three new families of planar central configurations for the 5-body problem with the
following properties: three bodies are on the vertices of an equilateral triangle and the other two bodies are on a perpendicular
bisector. 相似文献