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841.
A. N. Kuznetsov I. P. Sokolova I. P. Moroz V. M. Kobzova O. V. Sheremeta 《Izvestiya Physics of the Solid Earth》2007,43(4):309-313
The seismoelectric effects of the first and second kinds of oil and gas reservoir rocks are studied in three geological regions. Rock samples were taken from deep borehole cores of terrigenous and carbonate composition. Measurements were made in the ultrasound range (100–200 kHz) and at a frequency of 300 Hz. It is shown that the relationship between the porosity coefficient and the intensity of the second-kind seismoelectric effect is the same for terrigenous reservoir rocks in the Saratov Zavolzh’e region, an area of Western Siberia, and the Dnieper-Donets basin. An anomalously strong seismoelectric effect of the first kind (a vibration-induced change in the electrical resistance) is discovered for carbonate reservoir rocks of the Zavolzh’e region. 相似文献
842.
The device described in this paper, known as the traversing erosion beam, is believed to be the first to be designed specifically for measuring rates of downwearing of cohesive foreshores, such as clay shore platforms, under high‐energy wave conditions. It is primarily constructed of Flexlink Aluminium Structural System components and consists of a horizontal beam with a main leg and two further support legs. A sliding ‘dolly’ module is moved along the beam at precise intervals using a longitudinal scale as a reference. The topographic profile of the measurement surface is transferred to the dolly by a vertical sliding steel alloy rod, from which the relative height differences are measured by a separate engineer's digital height gauge placed on the dolly. The main leg of the device fits into a marine grade stainless steel box, which is deeply embedded into the foreshore or shore platform to act a permanent datum. The box is robust and can be expected to have a lifetime of at least a year, and possibly even five years or more. Sample data are provided from a clay shore platform at Warden Point in the Isle of Sheppey, Kent (UK), which demonstrate that the TEB can provide information on seasonal as well as annual rates of downwearing. The device has also been tested successfully on a peat and clay foreshore at Pett Level in Sussex and on a shore platform cut in glacial till at Easington, Yorkshire. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
843.
A seismic design procedure that does not take into account the maximum and cumulative plastic deformation demands that a structure is likely to undergo during severe ground motion could lead to unsatisfactory performance. In spite of this, current design procedures do not take into account explicitly the effect of low‐cycle fatigue. Based on the high correlation that exists between the strength reduction factor and the energy demand in earthquake‐resistant structures, simple procedures can be formulated to estimate the cumulative plastic deformation demands for design purposes. Several issues should be addressed during the use of plastic energy within a practical performance‐based seismic design methodology. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
844.
C. Vigny J. Chéry T. Duquesnoy F. Jouanne J. Ammann M. Anzidei J.-P. Avouac F. Barlier R. Bayer P. Briole E. Calais F. Cotton F. Duquenne K. L. Feigl G. Ferhat M. Flouzat J.-F. Gamond A. Geiger A. Harmel M. Kasser M. Laplanche M. Le Pape J. Martinod G. Ménard B. Meyer J.-C. Ruegg J.-M. Scheubel O. Scotti G. Vidal 《Journal of Geodesy》2002,76(2):63-76
The Western Alps are among the best studied collisional belts with both detailed structural mapping and also crustal geophysical
investigations such as the ECORS and EGT seismic profile. By contrast, the present-day kinematics of the belt is still largely
unknown due to small relative motions and the insufficient accuracy of the triangulation data. As a consequence, several tectonic
problems still remain to be solved, such as the amount of N–S convergence in the Occidental Alps, the repartition of the deformation
between the Alpine tectonic units, and the relation between deformation and rotation across the Alpine arc. In order to address
these problems, the GPS ALPES group, made up of French, Swiss and Italian research organizations, has achieved the first large-scale
GPS surveys of the Western Alps. More than 60 sites were surveyed in 1993 and 1998 with a minimum observation of 3 days at
each site. GPS data processing has been done by three independent teams using different software. The different solutions
have horizontal repeatabilities (N–E) of 4–7 mm in 1993 and 2–3 mm in 1998 and compare at the 3–5-mm level in position and
2-mm/yr level in velocity. A comparison of 1993 and 1998 coordinates shows that residual velocities of the GPS marks are generally
smaller than 2 mm/yr, precluding a detailed tectonic interpretation of the differential motions. However, these data seem
to suggest that the N–S compression of the Western Alps is quite mild (less than 2 mm/yr) compared to the global convergence
between the African and Eurasian plate (6 mm/yr). This implies that the shortening must be accomodated elsewhere by the deformation
of the Maghrebids and/or by rotations of Mediterranean microplates. Also, E–W velocity components analysis supports the idea
that E–W extension exists, as already suggested by recent structural and seismotectonic data interpretation.
Received: 27 November 2000 / Accepted: 17 September 2001 相似文献
845.
846.
Progress in Carrier Phase Time Transfer 总被引:1,自引:0,他引:1
Jim Ray Felicitas Arias Gérard Petit Tim Springer Thomas Schildknecht Jon Clarke Jan Johansson 《GPS Solutions》2001,4(4):47-54
The progress of the joint Pilot Project for time transfer, formed by the International GPS Service (IGS) and the Bureal International
des Poids et Mesures (BIPM), was recently reviewed. Three notable milestones were set. (1) The IGS will implement, at least
in a test mode, an internally realized time scale based on an integration of combined frequency standards within the IGS network.
This will eventually become the reference time scale for all IGS clock products (instead of the current GPS broadcast time).
(2) A new procedure for combined receiver and satellite clock products will be implemented officially in November 2000. Receiver
clocks are an entirely new product of the IGS. (3) The BIPM will coordinate an effort to calibrate all Ashtech Z12-T (and
possibly other) receivers suitable for time transfer applications, either differentially or absolutely. Progress reports will
be presented publicly in the spring 2001. ? 2001 John Wiley & Sons, Inc. 相似文献
847.
Laser-based validation of GLONASS orbits by short-arc technique 总被引:1,自引:0,他引:1
F. Barlier C. Berger P. Bonnefond P. Exertier O. Laurain J. F. Mangin J. M. Torre 《Journal of Geodesy》2001,75(11):600-612
The International GLONASS Experiment (IGEX-98) was carried out between 19 October 1998 and 19 April 1999. Among several objectives
was the precise orbit determination of GPS and GLONASS satellites and its validation by laser ranging observations. Local
laser-based orbit corrections (radial, tangential and normal components in a rotating orbital local reference frame) are computed
using a geometrical short-arc technique. The order of magnitude of these corrections is at the level of few decimeters, depending
on the considered components. The orbit corrections are analyzed as a function of several parameters (date, orbital plane,
geographical area). The mean corrections are at the level of several centimeters. However, when averaging over the entire
campaign and for all the satellites, no mean radial, tangential and normal orbit corrections are found. The origin of the
observed corrections is considered (errors due to the geocentric gravitational constant, the non-gravitational forces, the
thermal equilibrium of on-board equipment, the reference systems, the location and the signature of the retroreflector array,
and the precision of the satellite laser ranges). Some features are also due to errors in the radio-tracking GLONASS orbits.
Further investigations will be needed to better understand the origin of various biases.
Received: 17 February 2000 / Accepted: 31 January 2001 相似文献
848.
We investigated the effect of two different spatial scales of climate change scenarios on crop yields simulated by the EPIC crop model for corn, soybean, and wheat, in the central Great Plains of the United States. The effect of climate change alone was investigated in Part I. In Part II (Easterling et al., 2001) we considered the effects ofCO2 fertilization effects and adaptation in addition to climate change. The scenarios were formed from five years of control and 2 ×CO2 runs of a high resolution regional climate model (RegCM) and the same from an Australian coarse resolution general circulation model (GCM), which provided the initial and lateral boundary conditions for the regional model runs. We also investigated the effect of two different spatial resolutions of soil input parameters to the crop models. We found that for corn and soybean in the eastern part of the study area, significantly different mean yield changes were calculated depending on the scenario used. Changes in simulated dryland wheat yields in the western areas were very similar, regardless of the scale of the scenario. The spatial scale of soils had a strong effect on the spatial variance and pattern of yields across the study area, but less effect on the mean aggregated yields. We investigated what aspects of the differences in the scenarios were most important for explaining the different simulated yield responses. For instance, precipitation changes in June were most important for corn and soybean in the eastern CSIRO grid boxes. We establish the spatial scale of climate changescenarios as an important uncertainty for climate change impacts analysis. 相似文献
849.
O. P. Singh 《Meteorology and Atmospheric Physics》2001,78(1-2):1-9
Summary
El Ni?o/Southern Oscillation (ENSO) is known to cause world-wide weather anomalies. It influences the Indian Monsoon Rainfall
(IMR) also. But due to large spatial and temporal variability of monsoon rains, it becomes difficult to state any single uniform
relationship between the ENSO and IMR that holds good over different subdivisions of India, though the general type of relationship
between all India monsoon rainfall and ENSO is known since long. The selection of the most suitable ENSO index to correlate
with the IMR is another problem. The purpose of the present study is twofold, namely, to examine the relationship between
the ENSO and IMR for entire monsoon season by using an ENSO index which represents the ENSO phenomenon in a comprehensive
way, namely, the Multivariate ENSO Index (MEI) and to establish the relationships between MEI and IMR for every meteorological
subdivision of India for each monsoon month; i.e. June, July, August and September. A comparison of MEI/IMR correlations has
been made with Southern Oscillation Index (SOI)/IMR correlations. The result may find applications in the long range forecasting
of IMR on monthly and subdivisional scales, especially over the high monsoon rainfall variability regions of Northwestern
and the Peninsular India.
Received October 27, 2000 相似文献
850.
Two regional climate models have been applied to the task of generating an ensemble of realizations of the year 1982 with
observed boundary conditions in areas covering parts of the Mediterranean countries. These realizations were generated by
applying boundary conditions from the ECMWF ERA reanalysis project consecutively, carrying over the soil variables from the
regional models from one iteration to the next. Monthly mean fields for six iterations of each model have been used as statistical
ensembles in order to investigate the internal variability of the regional model dynamics. This internal variability is a
necessary consequence of the non-linear physical feedback mechanisms of the RCM being active. A small value of internal variability
will give better statistics for climate sensitivity signals, but will make these results less credible. The internal variability
is important for the quantitative assessment of a climate sensitivity signal. With the present choice of models and integration
domains the internal variabilities of surface fields and precipitation do reach levels that are less than, but in summer of
comparable order of magnitude to, corresponding atmospheric variabilities of an atmospheric general circulation model.
Received: 26 October 1999 / Accepted: 18 December 2000 相似文献