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141.
de Jesús Arrieta Baldovino Jair dos Santos Izzo Ronaldo Luis Rose Juliana Lundgren Avanci Mônica Angélica 《Geotechnical and Geological Engineering》2021,39(6):4655-4657
Geotechnical and Geological Engineering - 相似文献
142.
Peixoto Filho Flávio Tito Vargas Junior Euripedes do Amaral Santos Erick Slis Raggio Ferreira Francisco Henriques 《Geotechnical and Geological Engineering》2021,39(6):4127-4142
Geotechnical and Geological Engineering - In coring operations, core jamming is a permanent concern, taking place when the rock core sample becomes stuck within the inner core barrel, thus... 相似文献
143.
Ray-traced slant factors for mitigating the tropospheric delay at the observation level 总被引:3,自引:2,他引:1
Landon?UrquhartEmail author Felipe?G.?Nievinski Marcelo?C.?Santos 《Journal of Geodesy》2012,86(2):149-160
Three-dimensional ray tracing through a numerical weather model has been applied to a global precise point positioning (PPP)
campaign for modeling both the elevation angle- and azimuth-dependence of the tropospheric delay. Rather than applying the
ray-traced slant delays directly, the delay has been parameterized in terms of slant factors, which are applied in a similar
manner to traditional mapping functions, but which can account for the azimuthal asymmetry of the delay. Five strategies are
considered: (1) Vienna Mapping Functions 1 (VMF1) and estimation of a residual zenith delay parameter; (2) VMF1, estimation
of a residual zenith delay and estimation of two tropospheric gradient parameters; (3) three-dimensional ray-traced slant
factors and estimation of a residual zenith delay; (4) using only ray-traced slant factors and no estimation of any tropospheric
parameters and; (5) using both ray-traced slant factors and estimating a residual zenith delay and two tropospheric gradient
parameters. The use of the ray-traced slant factors (solution 3) showed a 3.8% improvement in the repeatability of the up
component when compared to the assumption of a symmetric atmosphere (solution 1), while the estimation of two tropospheric
gradient parameters gave the best results showing an 7.6% improvement over solution 1 in the up component. Solution 4 performed
well in the horizontal domain, allowing for sub-centimeter repeatability but the up component was degraded due to deficiencies
in the modeling of the zenith delay, particularly for stations located at equatorial latitudes. The magnitude of the differences
in the mean coordinates between solution 2 and solution 3, and the strong correlation with the differences between the north
component and the ray-traced gradients (coefficient of correlation of 0.83), as well as the impact of observation geometry
on the gradient solution indicate that the use of the ray-traced slant factors could have an implication on the realization
of reference frames. The estimated tropospheric products from the PPP solutions were compared to those derived from ray tracing.
For the zenith delay, a root mean square (RMS) of 5.4 mm was found, while for the gradient terms, a correlation coefficient
of 0.46 for the N–S and 0.42 for the E–W was found for the north–south and east–west components, suggesting that there are
still important differences in the gradient parameters which could be due to either errors in the NWM or to non-tropospheric
error sources leaking into the PPP-estimated gradients. 相似文献
144.
Juske Horita António M. dos Santos Christopher A. Tulk Bryan C. Chakoumakos Veniamin B. Polyakov 《Physics and Chemistry of Minerals》2010,37(10):741-749
A neutron powder diffraction study of hydrogenated and deuterated brucite was conducted at ambient temperature and at pressures
up to 9 GPa, using a Paris–Edinburgh high-pressure cell at the WAND instrument of the ORNL High Flux Isotope Reactor. The
two materials were synthesized by the same method and companion measurements of neutron diffraction were conducted under the
same conditions. Our refinement results show that the lattice-parameters of the a axis, parallel to the sheets of Mg–O octahedra, decrease only slightly with pressure with no effect of H–D substitution.
However, the c axis of Mg(OD)2 is shorter and may exhibit greater compressibility with pressure than that of Mg(OH)2. Consequently, the unit-cell volume of deuterated brucite is slightly, but systematically smaller than that of hydrogenated
brucite. When fitted to a third-order Birch–Murnaghan equation in terms of the normalized unit-cell volume, values of the
bulk modulus for hydrogenated and deuterated brucite (K
0 = 39.0 ± 2.8 and 40.4 ± 1.3 GPa, respectively) are, however, indistinguishable from each other within the experimental errors.
The measured effect of H–D substitution on the unit-cell volume also demonstrates that brucite (and other hydrous minerals)
preferentially incorporate deuterium over hydrogen under pressure, suggesting that the distribution of hydrogen isotopes in
deep-earth conditions may differ significantly from that in near-surface environments. 相似文献
145.
146.
Augusto César Coelho Dias da Silva Jaqueline Comin de Castilhos Erik Allan Pinheiro dos Santos Luciana Sonnewend Brondízio Leandro Bugoni 《Ocean & Coastal Management》2010,53(9):570-576
The neritic waters of the state of Sergipe in Northeastern Brazil is adjacent to the main nesting area of the olive ridley sea turtles (Lepidochelys olivacea) in the Western Atlantic Ocean and an important area for shrimp trawl fishery. To address the problem of incidental mortality of sea turtles captured during trawling and reduce the risk of overexploitation of shrimp stocks, Projeto TAMAR/ICMBio, a Brazilian sea turtle conservation program, has adopted two main strategies: (1) the implementation of a marine monitoring program and (2) active participation in local forums. This paper describes the conflicts among stakeholders, the arrangements and established mechanisms of negotiation aimed to protect sea turtles and shrimp grounds, and strategies to reduce conflicts between user groups. The analysis of this co-management process highlights the importance of stakeholder participation in resource management decision-making through a cooperative process, the role assumed by non-governmental organizations as mediators, and the factors that influence this system. The key factors and actions learnt from the current study include clear identification of the conflicts, identification of stakeholders – both local and external, and local leaders, encouragement of actors and leaders to participate, support and strengthening of local groups, legitimization of the discussion forums through involvement with government, formalization of decisions taken through legislation, and monitoring of the management efficacy. 相似文献
147.
148.
This paper discusses some geochemical mapping techniques and their effectiveness in detecting of gold and its pathfinder's geochemical anomalies. The study area (Marrancos area) is situated in Northern Portugal. Gold occurs in a quartz breccia with pyrite and arsenopyrite hosted by metamorphic rocks (hornfels) and it is present in these two sulphide minerals as inclusions or disseminated in the crystal lattice. In this area, the geochemical anomalies obtained by isoconcentration mapping of single elements were difficult to interpret. The use of alternative geochemical mapping such as multielement halos (additive halos) proved to be effective in the definition of Au, As, Bi, Sb, Te and Se secondary geochemical signature. 相似文献
149.
Lieu R Bonamente M Mittaz JP Durret F Dos Santos S Kaastra JS 《The Astrophysical journal》1999,527(2):L77-L80
The EUV excess emission from the clusters A2199 and A1795 remains an unexplained astrophysical phenomenon. There has been many unsuccessful attempts to "trivialize" the findings. In this Letter, we present direct evidence proving that the most recent of such attempts, which attributes the detected signals to a background nonuniformity effect, is likewise excluded. We address the issue by a reobservation of A2199 that features a new filter orientation, usage of a more sensitive part of the detector, and, most crucially, the inclusion of a background pointing at approximately 2 degrees offset-the first in situ measurement of its kind. We first demonstrate quantitatively two facts: (1) the offset pointing provides an accurate background template for the cluster observation, while (2) data from other blank fields do not. We then performed a point-to-point subtraction of the in situ background from the cluster field, with an appropriate propagation of errors. The resulting cluster radial profile is consistent with that obtained by our original method of subtracting a flat asymptotic background. The emission now extends to a radius of 20&arcmin;; it confirms the rising prominence of EUV excess beyond approximately 5&arcmin; as previously reported. 相似文献
150.
Ayan Santos Fleischmann Vinícius Alencar Siqueira Sly Wongchuig-Correa Walter Collischonn Rodrigo Cauduro Dias De Paiva 《水文科学杂志》2020,65(8):1358-1373
ABSTRACT This study provides a spatio-temporal analysis of the great floods that occurred in South America in 1983 using hydrometeorological data and outputs from a continental-scale hydrological-hydrodynamic model. In the extreme year 1983, there were three main flooding periods (February, June and July) in many South American river basins, such as the Araguaia, Tocantins, São Francisco, Uruguay, La Plata and its tributaries, resulting in high discharge of the Paraguay River for many months. Depth–area–duration curves show that 3-day precipitation events in northern regions of South America were among the largest 15 events in the period 1980–2015 but only for specific locations, whereas in southern areas, the most extreme events in the same period were for larger durations (≥7-day precipitation). Modelled total export of water volume to the oceans indicates that rivers draining to the South Atlantic reached an anomaly of 3.7 during 1983, followed by 1998 (1.9) and 1992 (1.1), all of them corresponding to El Niño years. 相似文献