A crustal deforming agent and the mechanism of the volcanic activity in the Azores     

A. A. De Mendonça Dias 《Bulletin of Volcanology》1959,21(1):95-102

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One dimensional elastic wave propagation in a non-homogeneous conical rod     

P. R. Sengupta  S. N. De 《Pure and Applied Geophysics》1972,99(1):17-22

Summary A one dimensional problem concerning the wave propagation in a non-homogeneous conical rod having its cross-section directly proportional to the square of the distance from a chosen point is considered in this paper. One end of the rod is subjected to a pressure step while the other end is stress free and the pulse shape is examined when the propagation speed of the wave has a particular continuous distribution over the entire rod.  相似文献   

Forced vibration of a thin non-homogeneous circular plate having a central hole     

Sasadhar De 《Pure and Applied Geophysics》1970,80(1):84-91

Summary This paper deals with the forced vibration produced in a thin non-homogeneous circular plate having a central hole when a periodic force is acting on the internal boundary.  相似文献   

Temperature measurement with a sonic anemometer and its application to heat and moisture fluxes     

Schotanus  P.  Nieuwstadt  F.T.M.  De Bruin  H.A.R. 《Boundary-Layer Meteorology》1983,26(1):81-93

Boundary-Layer Meteorology - The possibility of measuring heat and moisture fluxes using sonic anemometer data is investigated. Theoretical relations for the temperature variance and heat flux are...  相似文献   

Laboratory actinide partitioning: Whitlockite/liquid and influence of actinide concentration levels     

T.M. Benjamin  J.H. Jones  W.R. Heuser  D.S. Burnett 《Geochimica et cosmochimica acta》1983,47(10):1695-1705

Fission and alpha track radiography techniques have been used to measure partition coefficients (D) at trace (ppm) concentration levels for the actinide elements Th, U, and Pu between synthetic whitlockite and coexisting “haplobasaltic” silicate liquid at 1 bar pressure and 1250°C at oxygen fugacities from 10^?8.5 and 10^?0.7 bars. Pu is much more readily incorporated into crystalline phases than is U or Th under reducing conditions (fO₂ = 10^?8.5), because Pu is primarily trivalent, whereas U and Th are tetravalent. Definitive valence state assignments cannot be made, but our best estimates of corrected partition coefficients for Pu⁺³, Pu⁺⁴, Th⁺⁴, U⁺⁴, and U⁺⁶ are, for whitlockite 3.6/<?0.6/1.2/0.5/?0.002. The effect of changing pressure and liquidus temperature is relatively small, which probably reflects a weak temperature dependence for D (whitlockite) but possibly could be due to cancellation of opposing temperature and pressure effects. Comparison of experiments at trace U levels with those containing percent concentrations of UO₂ indicate that Si is involved in the substitution of U in whitlockite with U + 2Si ? Ca + 2P being the most likely mechanism. D_u is lower. 0.3 vs 0.5. at percent levels compared to 20 ppm. This is best explained by the effect of U on melt structure or by a decrease in the fraction of tetravalent U at high U concentrations.  相似文献   

Crystallization trends of pyroxenes from alkaline subvolcanites of Punta delle Pietre Nere (Gargano,Southern Italy)     

Maria De Fino  L. La Volpe  G. Piccarreta 《Mineralogy and Petrology》1982,29(3):177-192

Summary The results of microprobe analyses of clinopyroxenes from alkaline melasyenites and layered melagabbros, produced by intra-plate magmatism of Paleocene age at Punta delle Pietre Nere, are here given and discussed.The analysed pyroxenes range from diopsidic to acmite-rich compositions.The first crystallized pyroxenes (diopside) show Al^VI contents suggesting shallow depths of crystallization. In addition pyroxenes from melasyenite and those from melagabbro display different Cr contents, Al/Ti and Mg/(Mg+Fe²⁺+Fe³⁺) ratios confirming their crystallization from melts produced by different parental liquids.Diopsides and salites show an overall trend towards high Al, Ti and Fe³⁺, suggesting that the crystallization occurred under decreasing SiO₂/Al₂O₃ ratios and under relatively highpH₂O–pO₂ conditions.Pyroxenes from the Pietre Nere melasyenite show a progressive variation towards acmite rich compositions at Mg/(Mg+Fe²⁺+Fe³⁺) lower than 0.5; those from the layered melagabbro, instead, show a continuous enrichment in Ca Fe³⁺ AlSiO₆. This different behaviour is due to the co-crystallization, with the latest pyroxenes, of phases with different K/Na and Si/Al ratios.

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Kristallisations-Tendenzen der Pyroxene aus Alkali-Subvulkaniten auf Punta delle Pietre Nere (Gargano, Süditalien)

Zusammenfassung Es werden die Ergebnisse der Mikrosonden-Untersuchungen von Klinopyroxenen aus Alkali-Melasyeniten und schichtigen Alkali-Melagabbros, die durch Intra-plate-Magmatismus paläozenen Alters auf Punta delle Pietre Nere entstanden sind, beschrieben und erörtert.Die untersuchten Pyroxene reichen von diopsidischen bis zu Akmit-reichen Zusammensetzungen.Die zuerst kristallisierten Pyroxene (Diopsid) zeigen Al^VI-Gehalte, die auf geringe Tiefe des Kristallisationsvorganges hinweisen. Dazu zeigen die Pyroxene aus dem Melasyenit und aus dem Melagabbro unterschiedliche Cr-Gehalte; die Al/Ti- und Mg/(Mg+Fe²⁺+Fe³⁺)-Verhältnisse bestätigen deren Kristallisation aus Schmelzen, die aus unterschiedlichen Ursprungsmagmen stammen.Die Diopside und Salite zeigen eine einheitliche Tendenz zu hohem Al-, Ti- und Fe³⁺-Gehalt; dies deutet darauf hin, daß die Kristallisation unter abnehmenden SiO₂/Al₂O₃-Verhältnissen und unter relativ hohenpH₂O–pO₂-Bedingungen stattfand.Die Pyroxene aus dem Punta delle Pietre Nere-Melasyenit zeigen eine zunehmende Änderung zu Akmit-reichen Zusammensetzungen bei weniger als 0,5 Mg/(Mg+Fe²⁺+Fe³⁺); die Pyroxene aus dem schichtig differenzierten Melagabbro zeigen dagegen eine allmähliche Zunahme von CaFe³⁺AlSiO₆. Dieses unterschiedliche Verhalten rührt daher, daß Mineralphasen mit unterschiedlichen K/Na- und Si/Al-Verhältnissen zugleich mit den zuletzt gebildeten Pyroxenen kristallisierten.

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With 6 Figures  相似文献   

Tropical systematic and random error energetics based on NCEP (MRF) analysis-forecast system — A barotropic approach     

S. De  D. R. Chakraborty 《Journal of Earth System Science》2004,113(2):167-195

Systematic and random error and their growth rate and different components of growth rate budget in energy/variance form are investigated at wavenumber domain for medium range tropical (30‡S-30‡N) weather forecast using daily horizontal wind field of 850 hPa up to 5-day forecast for the month of June, 2000 of NCEP (MRF) model. Part I of this paper deals with the study at physical domain. The following are the major findings in this paper:

–	•Tropical systematic error is associated with large scale wave of wavenumber 2, unlike the tropical random error, in which case dominant spectra of random error are observed at higher spectral band of wavenumbers 4–7 in comparison to that of systematic error.
–	•Systematic error growth rate peak is observed at wavenumber 2 up to 4-day forecast then the peak is shifted to wavenumber 1 at 5-day forecast. Random error energy shows maximum growth at wavenumber 4 for 2-day forecast, wavenumber 6 for 3–4 day forecasts and at wavenumber 7 for 1-day and 5-day forecasts.
–	•In the error growth rate budget, flux of systematic error shows the net increase of error energy at wavenumber 1 through the triad interactions with the pairs of waves of other wavenumbers. Flux and pure generation of random error energy are found to be accumulated at wavenumber 4. Resolving the possible triads in wavenumber 4 associated with these terms, it is shown that the wave receives more energy from the pairs of waves of different wavenumbers than it loses, leading to the error energy peak at wavenumber 4. However, the significant triad interaction occurs among the wavenumber 2 and higher wavenumbers in systematic error energy flux.

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A comparison of a Hi/Lo GPS constellation with a populated conventional GPS constellation in support of RTK: A covariance analysis     

Benjamin?W.?RemondiEmail author  R.?Grover Brown 《GPS Solutions》2004,8(2):82-92

This study makes an initial comparison of three GPS-like constellations. Starting with a simplified constellation of 25 GPS satellites as a reference, GPS(25), we determine what kinematic positioning improvements would result from a constellation comprising a Hi component of 16 GPS satellites (at roughly 16.8 earth radii) coupled with a Lo component of 49 GPS satellites (at roughly 2.1 earth radii). We also include a GPS constellation of 49 GPS satellites, GPS(49), which comprises orbits like the GPS(25) constellation. The GPS(49) and the Hi(16)/Lo(49) constellations have semi-major axes selected so that they have exactly the same average number of satellites above 7.5 degrees elevation (averaged over 24 hours). What motivated this study was a need to measure the benefits, to precision differential kinematic positioning methods (i.e., RTK), which result from the higher Doppler shifts (hence speedier integrated Doppler) generated by the Lo component. Quicker initial convergence was anticipated, of course.  相似文献   

3-D Modelling of Campi Flegrei Ground Deformations: Role of Caldera Boundary Discontinuities     

Fran?ois?Beauducel  Giuseppe De?Natale  Franco?Obrizzo  Folco?PingueEmail author 《Pure and Applied Geophysics》2004,161(7):1329-1344

Campi Flegrei is a caldera complex located west of Naples, Italy. The last eruption occurred in 1538, although the volcano has produced unrest episodes since then, involving rapid and large ground movements (up to 2 m vertical in two years), accompanied by intense seismic activity. Surface ground displacements detected by various techniques (mainly InSAR and levelling) for the 1970 to 1996 period can be modelled by a shallow point source in an elastic half-space, however the source depth is not compatible with seismic and drill hole observations, which suggest a magma chamber just below 4 km depth. This apparent paradox has been explained by the presence of boundary fractures marking the caldera collapse. We present here the first full 3-D modelling for the unrest of 1982–1985 including the effect of caldera bordering fractures and the topography. To model the presence of topography and of the complex caldera rim discontinuities, we used a mixed boundary elements method. The a priori caldera geometry is determined initially from gravimetric modelling results and refined by inversion. The presence of the caldera discontinuities allows a fit to the 1982–1985 levelling data as good as, or better than, in the continuous half-space case, with quite a different source depth which fits the actual magma chamber position as seen from seismic waves. These results show the importance of volcanic structures, and mainly of caldera collapses, in ground deformation episodes.  相似文献   

Application of a Bayesian approach to stochastic delineation of capture zones   总被引：1，自引：0，他引：1  

Feyen L  Dessalegn AM  De Smedt F  Gebremeskel S  Batelaan O 《Ground water》2004,42(4):542-551

This paper presents a Bayesian Monte Carlo method for evaluating the uncertainty in the delineation of well capture zones and its application to a wellfield in a heterogeneous, multiaquifer system. In the method presented, Bayes' rule is used to update prior distributions for the unknown parameters of the stochastic model for the hydraulic conductivity, and to calculate probability-based weights for parameter realizations using head residuals. These weights are then assigned to the corresponding capture zones obtained using forward particle tracking. Statistical analysis of the set of weighted protection zones results in a probability distribution for the capture zones. The suitability of the Bayesian stochastic method for a multilayered system is investigated, using the wellfield Het Rot at Nieuwrode, Belgium, located in a three-layered aquifer system, as an example. The hydraulic conductivity of the production aquifer is modeled as a spatially correlated random function with uncertain parameters. The aquitard and overlying unconfined aquifer are assigned random, homogeneous conductivities. The stochastic results are compared with deterministic capture zones obtained with a calibrated model for the area. The predictions of the stochastic approach are more conservative and indicate that parameter uncertainty should be taken into account in the delineation of well capture zones.  相似文献