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181.
182.
Giancarlo Della Ventura G. Diego Gatta Gunter J. Redhammer Fabio Bellatreccia Anja Loose Gian Carlo Parodi 《Physics and Chemistry of Minerals》2009,36(4):193-206
We relate a single-crystal FTIR (Fourier transform infrared) and neutron diffraction study of two natural cancrinites. The structural refinements show that the oxygen site of the H2O molecule lies off the triad axis. The water molecule is almost symmetric and slightly tilted from the (0001) plane. It is involved in bifurcated hydrogen bridges, with Ow···O donor–acceptor distances >2.7 Å. The FTIR spectra show two main absorptions. The first at 3,602 cm?1 is polarized for E ⊥ c and is assigned to the ν3 mode. The second, at 3,531 cm?1, is also polarized for E ⊥ c and is assigned to ν1 mode. A weak component at 4,108 cm?1 could possibly indicate the presence of additional OH groups in the structure of cancrinite. Several overlapping bands in the 1,300–1,500 cm?1 range are strongly polarized for E ⊥ c, and are assigned to the vibrations of the CO3 group. 相似文献
183.
We have conducted detailed rock magnetic experiments on samples from loess unit 8 (L8) and paleosol unit 8 (S8) in Jingbian,
Yichuan and Duanjiapo loess sections along an N-S transect in the Chinese Loess Plateau. Major rock magnetic results are as
follows: (i) An increase of high field susceptibility (χh) in the same level of loess or paleosol from north to south is observed, suggesting an enhancement of pedogenesis. (ii) The
low field susceptibility(χL) in loess unit L8 is almost the same in three sections. In contrast, the χL of paleosol unit S8 in Yichuan is highest, and the χL of Duanjiapo is lower than that in Yichuan section, suggesting that there is not correlation between the χL and the degree of pedogenesis in loess-paleosols. (iii) With the increasing of χL, both the contents of the superparamagnetic (SP) and the ferrimagnetic grains in loess-paleosol increase, however, the enhancement
of magnetic susceptibility is probably dependent more on the increase of the ferrimagnetic concentration than on a change
in the grain size. (iv) The content of the maghemite in loess unit 8 increases from the northern to the southern part of the
Chinese Loess Plateau, and is positively correlated with the pedogenesis of the loess. 相似文献
184.
Mapping of Land-Atmosphere Heat Fluxes and Surface Parameters with Remote Sensing Data 总被引:3,自引:0,他引:3
A variational data assimilation scheme is used to infer two key parameters ofthe surface energy balance that control the partitioning of available energy intolatent, sensible, and ground heat fluxes (LE, H, and G). Remotely sensedland surface temperature (LST) is the principal data source. Maps ofdiurnal energy balance components are presented for a basin with varied landcover (Arno Basin, Italy) for a 18-day period in July 1996.Given available energy, the major unknown (dimensionless) parameters requiredfor partitioning among fluxes are: (1) Landscape effects on near-surfaceturbulence as captured by the bulk heat transfer coefficient CBN underneutral conditions and (2) surface control of the relative magnitudes of LEand H as represented by the evaporative fraction EF. The data assimilationscheme merges 1.1-km resolution remotely sensed LST images (based onoptical, thermal and microwave measurements from two different satelliteplatforms) into a parsimonious model of heat diffusion. Both the measurementsand the model predictions are considered uncertain. Posterior error statisticsthat represent uncertainty of the estimated parameters are also derived.Maps of CBN show spatial patterns consistent with the dominant land useand basin physiography. Daily maps of EF exhibit spatial variationscorresponding to land cover and land use – the day-to-day variations inEF show fluctuations consistent with rain events and drydowns experiencedduring the period. Based on these parameters and available environmentalvariables, maps of diurnal LE and H may be produced (in this paper daytimeLE maps are reported).The application demonstrates that remotely sensed land surface temperaturesequences contain significant amount of information of the partitioning ofavailable energy among the fluxes. The variational data assimilation frameworkis shown to be an efficient and parsimonious approach without reliance onempirical relationships such as those based on vegetation indices. 相似文献
185.
In the valley of Bamiyan, Afghanistan, approximately 1700 years ago, two large standing Buddha statues were carved out of the sedimentary rock of the region. They were 53 and 38 m high and the larger one figured as the tallest representation of a standing Buddha in the world. In March 2001 the Taleban government militia demolished the colossal statues. After the destruction a group from ETH Zürich completed the computer reconstruction of the Great Buddha, which can serve as the basis for a physical reconstruction. This paper reports the results of the image-based 3D reconstruction of the statue, performed on three different data-sets in parallel and using different photogrammetric techniques and algorithms. 相似文献
186.
Sensitivity of PSHA results to ground motion prediction relations and logic-tree weights 总被引:7,自引:0,他引:7
Fabio Sabetta Antonio Lucantoni Hilmar Bungum Julian J. Bommer 《Soil Dynamics and Earthquake Engineering》2005,25(4):317-329
Epistemic uncertainty in ground motion prediction relations is recognized as an important factor to be considered in probabilistic seismic hazard analysis (PSHA), together with the aleatory variability that is incorporated directly into the hazard calculations through integration across the log-normal scatter in the ground motion relations. The epistemic uncertainty, which is revealed by the differences in median values of ground motion parameters obtained from relations derived for different regions, is accounted for by the inclusion of two or more ground motion prediction relations in a logic-tree formalism. The sensitivity of the hazard results to the relative weights assigned to the branches of the logic-tree, is explored through hazard analyses for two sites in Europe, in areas of high and moderate seismicity, respectively. The analyses reveal a strong influence of the ground motion models on the results of PSHA, particularly for low annual exceedance frequencies (long return periods) and higher confidence levels. The results also show, however, that as soon as four or more relations are included in the logic-tree, the relative weights, unless strongly biased towards one or two relations, do not significantly affect the hazard. The selection of appropriate prediction relations to include in the analysis, therefore, has a greater impact than the expert judgment applied in assigning relative weights to the branches of the logic-tree. 相似文献
187.
188.
Fabio Crosilla 《Journal of Geodesy》1983,57(1-4):226-239
This paper proposes an original method of constructing a criterion matrix for the optimal design of control networks by means
of the contraction of the eigenvalues and the rotation of the eigenvectors of a covariance matrix. The rotation of the eigenvectors
is carried out by two different methods, that is through independent rotations of the pairs of the eigenvector matrix components
and through a procrustean transfomation of the same matrix. The required criterion is that the “essential eigenvector components”
must be as orthogonal as possible to the predicted direction of deformation. A Second Order Design problem is then resolved,
that is the optimization of the precision of the observations of a local free distance network to be constructed for the study
of recent crustal movements in the seismogenetic area of Friuli (Italy). The results obtained show a high degree of correspondence
for the two proposed methods of rotation if limited rotations of the eigenvectors are considered. 相似文献
189.
Giancarlo Della Ventura Fabio Bellatreccia Paolo Rossi 《Physics and Chemistry of Minerals》2007,34(10):727-731
We report here a single-crystal polarized-light study of stoppaniite, ideally (Fe,Al,Mg)4(Be6Si12O36)(H2O)2(Na,□), from Capranica (Viterbo). Polarized-light FTIR spectra were collected on an oriented (hk0) section, doubly polished
to 15 μm. The spectrum shows two main bands at 3,660 and 3,595 cm−1; the former is strongly polarized for E ⊥c, while the latter is polarized for E //c. A sharp and very intense band at 1,620 cm−1, plus minor features at 4,000 and 3,228 cm−1 are also polarized for E //c. On the basis of literature data and considering the pleochroic behavior of the absorptions, the 3,660 cm−1 band is assigned to the ν3 stretching mode and the 1,620 cm−1 (associated with an overtone 2*ν2 at 3,230 cm−1) band to the ν2 bending mode of “type II” water molecules within the structural channels of the studied beryl. The sharp band at 3,595 cm−1 is not associated with a corresponding ν2 bending mode; thus it is assigned to the stretching vibration of O–H groups in the sample. The minor 4,000 cm−1 feature can be assigned to the combination of the O–H bond parallel to c with a low-frequency metal-oxygen mode such as the Na–O stretching mode. The present results suggest that the interpretation
of the FTIR spectrum of Na-rich beryl needs to be carefully reconsidered. 相似文献
190.
José M. Carcione Martin Landrø Anthony F. Gangi Fabio Cavallini 《Geophysical Prospecting》2007,55(6):793-804
Hydrocarbon depletion and fluid injection cause compaction and stretching of the reservoir and overburden layers. 4D prestack seismic data can be used to detect these changes because compaction/stretching causes changes in traveltimes and seismic velocities. We show that, by using two different petro‐elastic models at varying effective pressures, a good approximation is to assume that the fractional changes in layer thickness, ΔL/L, and seismic velocity, Δv/v, are related by a linear function of ΔL/L. The slope of this function (the dilation factor, α= (Δv/v)/(ΔL/L) ) is negative and its absolute value generally decreases (shale, low porosity) or increases (sandstone, high porosity) with increasing layer thickness and decreasing effective pressure. The analysis is mainly performed for isotropic deformations. The dilation factor for uniaxial deformations is smaller in absolute value. The dilation factor, which can be calculated from time‐lapse data, can be used to predict reservoir compaction/stretching as a function of depth and surface subsidence. 相似文献