716 resultados para Oblique.


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The Upper Miocene stratigraphic succession of the Las Minas Basin, located at the external zone of the Betic Chain in SE Spain, preserves several examples of lake carbonate bench deposits. Excellent exposures of the carbonate benches allow detailed observation of the architecture of these sediments and provide new insights for the ‘‘steep-gradient bench margin–low energy’’ model proposed by Platt and Wright (1991). The lake carbonate benches developed in close association with fluvially dominated shallow deltas that exhibit typical Gilbert-type profiles. The delta sequences comprise bottomset prodelta marl facies, distal to proximal foreset facies, deposited mainly in a delta-front environment, and topset facies, the latter reflecting both subaqueous delta-front and subaerial delta-plain environments. The development of the carbonate benches was constrained by the convexupward morphology of the deltaic deposits, which led to the available accommodation space for the growth of the steep-gradient platforms. The benches display a progradational pattern characterized by sigmoid-oblique internal geometries and offlap upper boundary relationships, which suggests that the carbonate benches developed under slow though continuous lake-level rise. Both the dimensions of the benches and the dominant carbonate components (i.e., encrusted charophyte stems and calcified cyanobaterial remains), allow comparisons with the progradational marl benches recognized in modern temperate hardwater lakes. Accordingly, the case study presented here provides a good ancient sedimentary analog for low-energy lake carbonate benches. Moreover, the evolutionary trend inferred from the fossil example offers new insights into the depositional conditions of this type of sediment and allows recognition of the transitional pattern from bench to ramp carbonate lake margins.

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We analyzed surface-wave propagation that takes place at the boundary between a semi-infinite dielectric and a multilayered metamaterial, the latter with indefinite permittivity and cut normally to the layers. Known hyperbolization of the dispersion curve is discussed within distinct spectral regimes, including the role of the surrounding material. Hybridization of surface waves enable tighter confinement near the interface in comparison with pure-TM surface-plasmon polaritons. We demonstrate that the effective-medium approach deviates severely in practical implementations. By using the finite-element method, we predict the existence of long-range oblique surface waves.

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This sewn volume contains Noyes’ mathematical exercises in geometry; trigonometry; surveying; measurement of heights and distances; plain, oblique, parallel, middle latitude, and mercator sailing; and dialing. Many of the exercises are illustrated by carefully hand-drawn diagrams, including a mariners’ compass and moon dials.

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Leather hardcover notebook with unruled pages containing the handwritten mathematical exercises of William Emerson Faulkner, begun in 1795 while he was an undergraduate at Harvard College. The volume contains rules, definitions, problems, drawings, and tables on geometry, trigonometry, surveying, calculating distances, sailing, and dialing. Some of the exercises are illustrated by unrefined hand-drawn diagrams, including some of buildings and trees.

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Notebook containing the handwritten mathematical exercises of William Tudor, kept in 1795 while he was an undergraduate at Harvard College. The volume contains rules, definitions, problems, drawings, and tables on geometry, trigonometry, surveying, calculating distances, sailing, and dialing. Some of the exercises are illustrated with hand-drawn diagrams. The Menusration of Heights and Distances section contains color drawings of buildings and trees, and some have been altered with notes in different hands and with humorous additions. For instance, a drawing of a tower was drawn into a figure titled “Egyptian Mummy.” Some of the images are identified: “A rude sketch of the Middlesex canal,” Genl Warren’s monument on Bunker Hill,” “Noddles Island,” “the fields of Elysium,” and the “Roxbury Canal.” The annotations and additional drawings are unattributed.

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The achievement of deep penetration (562 m) of seafloor basalts at Hole 504B, near the Costa Rica Rift (1°13.63'N, 83°43.81'W), on DSDP Legs 69 and 70 presented a rare opportunity to examine the structure of young (6 m.y.) oceanic crust. In addition to the recovery of samples for laboratory studies, an extensive suite of downhole logs and experiments was carried out at this site, for two main purposes: (1) to allow reliable deductions about the nature of the entire section of penetrated crust, because recovery of samples was far from complete (-25%); (2) to probe the physical state of rock around the drilled hole on a scale of tens of meters to kilometers. Information on the latter large-scale phenomena at Hole 504B were provided mainly by the oblique seismic experiment, utilizing a bore-hole seismometer (Stephen 1983), and by the large-scale-electrical- resistivity experiment described below.

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In order to reconstruct past variations in the aeolian dust (Kosa) contribution to the Japan Sea, and to establish a direct link between terrestrial and marine climatic records, we have applied statistical procedures to distinguish and quantify detrital subcomponents within the detrital fraction of the late Quaternary hemipelagic sediments in the Japan Sea. Q-mode factor analysis with varimax and oblique rotation of the factors followed by multiple-regression analysis between mineral composition and factor loadings was conducted using six ''detrital'' elements. Four detrital subcomponents were defined, which are attributed to Kosa derived from ''typical'' loess, Kosa from ''weathered'' loess, and fine and coarse arc-derived detritus, respectively, based on comparisons with the chemical and mineral compositions of probable source materials. Using these detrital subcomponents, the variation in Kosa fraction was reconstructed for the last 200 ky. The results reveal millennial-scale as well as glacial-interglacial scale variations in Kosa contribution. Especially, millennial-scale variability of Kosa contribution suggests the presence of high frequency variation in summer monsoon precipitation in the central to east Asia during the last 200 ky.

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Drill core recovered at Ocean Drilling Program Site 808 (Leg 131) proves that the wedge of trench sediment within the central region of the Nankai Trough comprises approximately 600 m of hemipelagic mud, sandy turbidites, and silty turbidites. The stratigraphic succession thickens and coarsens upward, with hemipelagic muds and volcanic-ash layers of the Shikoku Basin overlain by silty and sandy trench-wedge deposits. Past investigations of clay mineralogy and sand petrography within this region have led to the hypothesis that most of the detritus in the Nankai Trough was derived from the Izu-Honshu collision zone and transported southwestward via axial turbidity currents. Shipboard analyses of paleocurrent indicators, on the other hand, show that most of the ripple cross-laminae within silty turbidites of the outer marginal trench-wedge facies are inclined to the north and northwest; thus, many of the turbidity currents reflected off the seaward slope of the trench rather than moving straight down the trench axis. Shore-based analyses of detrital clay minerals demonstrate that the hemipelagic muds and matrix materials within sandy and silty turbidites are all enriched in illite; chlorite is the second-most abundant clay mineral, followed by smectite. In general, the relative mineral percentages change relatively little as a function of depth, and the hemipelagic clay-mineral population is virtually identical to the turbidite-matrix population. Comparisons between different size fractions (<2 µm and 2-6 µm) show modest amounts of mineral partitioning, with chlorite content increasing in the coarser fraction and smectite increasing in the finer fraction. Values of illite crystallinity index are consistent with conditions of advanced anchimetamorphism and epimetamorphism within the source region. Of the three mica polytypes detected, the 2M1 variety dominates over the 1M and 1Md polytypes; these data are consistent with values of illite crystallinity. Measurements of mica bo lattice spacing show that the detrital illite particles were eroded from a zone of intermediate-pressure metamorphism. Collectively, these data provide an excellent match with the lithologic and metamorphic character of the Izu-Honshu collision zone. Data from Leg 131, therefore, confirm the earlier interpretations of detrital provenance. The regional pattern of sediment dispersal is dominated by a combination of southwest-directed axial turbidity currents, radial expansion of the axial flows, oblique movement of suspended clouds onto and beyond the seaward slope of the Nankai Trough, and flow reflection back toward the trench axis.

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National Highway Traffic Safety Administration, Washington, D.C.

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Federal Highway Administration, Washington, D.C.

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National Highway Traffic Safety Administration, Washington, D.C.

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National Highway Traffic Safety Administration, Washington, D.C.

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National Highway Traffic Safety Administration, Washington, D.C.