A three-dimensional geophysical model of the crust in the Barents Sea region: model construction and basement characterization   总被引：2，自引：0，他引：2  

Oliver Ritzmann  Nils Maercklin  Jan Inge Faleide  Hilmar Bungum  Walter D. Mooney  Shane T. Detweiler 《Geophysical Journal International》2007,170(1):417-435

  相似文献   

Two-dimensional modelling of some CFC replacement compounds     

Oliver Wild  Oliver V. Rattigan  Roderic L. Jones  John A. Pyle  R. Anthony Cox 《Journal of Atmospheric Chemistry》1996,25(2):167-199

The Cambridge 2-D Eulerian model has been used to study the potential atmospheric distributions and lifetimes of a number of CFC replacement compounds and their degradation products. The study has focused on HFC 134a and HCFCs 123, 141b and 142b and the major products formed by their atmospheric degradation. The loss of these compounds and their products by hydroxyl radical attack, photolysis and in-cloud hydrolysis have been investigated. The study has shown that HCFCs 141b and 142b have sufficiently long lifetimes to enter the stratosphere in significant quantities, where degradation leads to an increase in the total stratospheric chlorine concentration. The study has also highlighted areas where further experimental work would be valuable, in particular characterisation of the product channels for the degradation reactions and determination of the removal rates of the products in the aqueous phase.  相似文献   

Stochastic perturbation analysis of groundwater flow. Spatially variable soils,semi-infinite domains and large fluctuations     

G. Christakos  C. T. Miller  D. Oliver 《Stochastic Environmental Research and Risk Assessment (SERRA)》1993,7(3):213-239

As is well known, a complete stochastic solution of the stochastic differential equation governing saturated groundwater flow leads to an infinite hierarchy of equations in terms of higher-order moments. Perturbation techniques are commonly used to close this hierarchy, using power-series expansions. These methods are applied by truncating the series after a finite number of terms, and products of random gradients of conductivity and head potential are neglected. Uncertainty regarding the number or terms required to yield a sufficiently accurate result is a significant drawback with the application of power series-based perturbation methods for such problems. Low-order series truncation may be incapable of representing fundamental characteristics of flow and can lead to physically unreasonable and inaccurate solutions of the stochastic flow equation. To support this argument, one-dimensional, steady-state, saturated groundwater flow is examined, for the case of a spatially distributed hydraulic conductivity field. An ordinary power-series perturbation method is used to approximate the mean head, using second-order statistics to characterize the conductivity field. Then an interactive perturbation approach is introduced, which yields improved results compared to low-order, power-series perturbation methods for situations where strong interactions exist between terms in such approximations. The interactive perturbation concept is further developed using Feynman-type diagrams and graph theory, which reduce the original stochastic flow problem to a closed set of equations for the mean and the covariance functions. Both theoretical and practical advantages of diagrammatic solutions are discussed; these include the study of bounded domains and large fluctuations.  相似文献   

Mean wind-direction shear through a forest canopy     

F. B. Smith  D. J. Carson  H. R. Oliver 《Boundary-Layer Meteorology》1972,3(2):178-190

The equations of motion applying to the wind field in a forest canopy are simplified to a balance between the shearing stress gradient and either the form-drag of the leaves in the upper dense canopy, or the overall horizontal pressure gradient in the more open space beneath. The equations imply that, in descending through the forest, the stress and wind vectors turn through an angle which depends on the forest characteristics and on the stability and the speed of the airflow above the forest. The turning is roughly confirmed by an overall average measured on a very flat site near Thetford, Norfolk, covered by an extensive uniform pine forest.  相似文献   

In-flight performance analysis of the CHAMP BlackJack GPS Receiver   总被引：8，自引：1，他引：7  

Oliver?MontenbruckEmail author  Remco?Kroes 《GPS Solutions》2003,7(2):74-86

JPL's BlackJack receiver currently represents the most widely used geodetic grade GPS receiver for space applications. Using data from the CHAMP science mission, the in-flight performance of the BlackJack receiver has been assessed and the impact of various software updates performed during the 2.5 years since launch is described. Key aspects of the study comprise the channel allocation, anomalous data points, and the noise level of the code and carrier data. In addition, it has been demonstrated that the code measurements collected onboard the CHAMP satellite are notably affected by multipath errors in the aft-looking hemisphere, which can be attributed to cross-talk between the occultation antenna string and the primary precise orbit determination antenna. For carrier smoothed 10 s normal points, the code noise itself varies between a minimum of 5 cm at high elevations and 0.5 m (C/A) to 1.0 m (P₁, P₂) at 10° elevation. Carrier-phase data exhibit representative errors of 0.2 to 2.5 mm. The results of the CHAMP GPS data analysis contribute to a better understanding and possible improvement of the BlackJack receiver and support the design of optimal data editing and weighting strategies in precise orbit determination applications.  相似文献   

GIOVE-A initial signal analysis     

Oliver Montenbruck  Christoph Günther  Sebastian Graf  Miquel Garcia-Fernandez  Johann Furthner  Hanspeter Kuhlen 《GPS Solutions》2006,10(2):146-153

In late December 2005 the GIOVE-A test satellite was launched by the European Space Agency (ESA) to secure the frequencies for the Galileo system and to provide a platform for testing the new navigation signals. We performed an initial assessment of these signals using the 30 m deep space antenna of the DLR ground station in Weilheim (Germany). The antenna gain raised the signals above the noise level, thus allowing a detailed analysis even without knowledge of the ranging codes. The present paper covers the analysis of the L1/E1 signals, which includes a discussion of the spectrum, the time domain signal and a decoding of the spreading codes for the Open Service.  相似文献   

Calculation of the Inverse of the Covariance     

Dean S. Oliver 《Mathematical Geology》1998,30(7):911-933

In reservoir characterization, the covariance is often used to describe the spatial correlation and variation in rock properties or the uncertainty in rock properties. The inverse of the covariance, on the other hand, is seldom discussed in geostatistics. In this paper, I show that the inverse is required for simulation and estimation of Gaussian random fields, and that it can be identified with the differential operator in regularized inverse theory. Unfortunately, because the covariance matrix for parameters in reservoir models can be extremely large, calculation of the inverse can be a problem. In this paper, I discuss four methods of calculating the inverse of the covariance, two of which are analytical, and two of which are purely numerical. By taking advantage of the assumed stationarity of the covariance, none of the methods require inversion of the full covariance matrix.  相似文献   

New equipment and processing for magnetotelluric remote reference observations   总被引：2，自引：0，他引：2  

Oliver Ritter  reas Junge  & Graham Dawes 《Geophysical Journal International》1998,132(3):535-548

Robust estimates of magnetotelluric and geomagnetic response functions are determined using the coherency and expected uniformity of the magnetic source field as quality criteria. The method is applied on data sets of three simultaneously recording sites. For the data acquisition we used a new generation of geophysical equipment (S.P.A.M. MkIII), which comprises novel concepts of parallel computing and networked, digital data transmission. The data-processing results show that the amount of noise on the horizontal components of the magnetic field varies considerably in time, between sites and over the frequency range. The removal of such contaminated data beforehand is essential for most data-processing schemes, as the magnetic channels are usually assumed to be free of noise. The standard remote reference method is aimed at reducing bias in response function estimates. However, this does not necessarily improve their precision as our results clearly show. With our method, on the other hand, we can filter out source field irregularities, thereby providing suitable working conditions for the robust algorithm, and eventually obtain considerably improved results. Contrary to previous concepts, we suggest rejecting as much data as feasible in order to concentrate on the remaining parts of high-quality observations.  相似文献   

Garnet growth in a metapelite from the Moinian rocks of Northern Sutherland,Scotland     

Carol A. Finlay  Alan Kerr 《Contributions to Mineralogy and Petrology》1979,71(2):185-191

Compositional profiles of a series of garnets, extracted from a pelitic schist occurring in the Moinian rocks of Northern Sutherland, have been established. The profiles are complex and do not conform to a simple fractionation model. A model to explain them is suggested.  相似文献   

Partial chemical characterization of estuarine dissolved organic matter     

Richard A. Kerr  James G. Quinn   《Organic Geochemistry》1980,2(3-4)

Activated charcoal chromatography was used to isolate dissolved organic matter from a series of water samples collected in Narragansett Bay, Rhode Island, during 1975–1976. The range of dissolved organic carbon values in the samples was 1.46–3.75 mg OC/1. A relatively constant amount of organic carbon was isolated giving overall recoveries of 23 to 63% (mean of 45%). The isolated organic matter was characterized by spectrophotometric measurements, stable carbon isotope determinations, and copper solubilizing capacities. In general, the isolated material displayed considerable constancy in terms of the parameters measured. However, several chemical variations were detected that were probably related to the introduction of organic matter from diatom blooms and terrigenous runoff.  相似文献