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21.
Séverine Bernardie Jean-Pascal Gilbert François Lebert Hubert Fabriol 《Pure and Applied Geophysics》2007,164(1):177-197
The monitoring of the stability of old mines constitutes an important research objective for our institution, BRGM. The study
reported here shows the contribution of high-frequency (>30 kHz) acoustic emissions to the detection of the damage within
a rock mass, during an experiment within a pilot site of an old flooded iron mine. The experiment consisted of recording all
the hydroacoustic events in a broad frequency band (between 30 Hz and 180 kHz), during 18 months. The monitoring network has
been calibrated by a triggered block fall that made it possible to highlight a relationship between the occurrence of high-frequency/low-frequency
hydroacoustic emissions and rock falls. The events recorded have been associated with the micro-failure of the rock mass near
the roof, prior to the detachment of the blocks. This monitoring showed important high-frequency hydroacoustic activity, which
may be associated with mechanical instabilities generated by the evolution of water pressure during the experiment. In conclusion,
the high-frequency hydroacoustic activity appears to be a good indicator of instability and, therefore, this new technique
constitutes a promising tool for monitoring abandoned underground cavities. 相似文献
22.
Contribution to the characterization and identification of low molecular weight organic substances in biologically treated effluent. In a review it is shown that by determination of sum parameters only 25% of low molecular weight substances <1000 Dalton in biologically treated effluent can be divided into different classes of compounds. A method is described to separate the low molecular weight compounds (freeze concentration, electrodialysis, vacuum evaporation, freeze drying) in order to identify single compounds. In a first GC-MS analysis 87 compounds, among them a high proportion of substances with hetero atoms, could be identified. Their concentrations lie between 0,1 and 3 μg/1. Only 3% of the low molecular weight fraction related to the DOC value is covered by the identified substances. Therefore it can be assumed, that a broad variety of low molecular weight compounds in very low concentrations is present in the effluent of biological treatment plants. 相似文献
23.
T. Gilbert 《Meteorology and Atmospheric Physics》1955,8(4):397-410
Zusammenfassung Das für die Bodenatmung wesentliche, bewegliche Luftvolumen wird in Abhängigkeit von der Tiefe aus der Absorption von Druckwellen im Boden abgeleitet. Zur Prüfung werden periodische Druckwellen künstlich erzeugt und in verschiedenen Erdbodentiefen gemessen und registriert.
Mit 5 Textabbildungen.
Die Arbeit wurde mit Unterstützung des Bundesministeriums für Ernährung, Landwirtschaft und Forsten und der Karlsruher Hochschulvereinigung durchgeführt. 相似文献
Summary The volume of moving air, which is essential for the respiration of the soil, has been calculated with the dependency on depth from absorption of pressure waves in the soil. The results have been controlled by experiments with artificial periodic pressure waves which are measured and registered at different depths in the soil.
Résumé Le volume d'air mouvant qui est d'importance essentielle pour la respiration du sol, est déduit de l'absorption d'ondes de pression dans le sol et de leur dépendance de la profondeur. Pour vérifier la théorie, l'auteur produit des ondes de pression artificielles et périodiques qui sont ensuite mesurées et enregistrées à diverses profondeurs.
Mit 5 Textabbildungen.
Die Arbeit wurde mit Unterstützung des Bundesministeriums für Ernährung, Landwirtschaft und Forsten und der Karlsruher Hochschulvereinigung durchgeführt. 相似文献
24.
A. D. Gilbert C. Froeschlé U. Frisch 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):263-272
Wavelet analysis is applied to distributions of points generated by iterating the standard map. The initial condition is chosen so that the points fill the largest chaotic region. When the standard map parameterk=1.3, the distribution of points contains many voids corresponding to islands in the chaotic region. The wavelet transform is dominated by contributions from these islands. Fork=10 the chaos fills phase space and no structure is apparent; the wavelet transform reveals statistical fluctuations in the distribution of points. 相似文献
25.
Generalized Ray Theory for a Layered Sphere 总被引:1,自引:0,他引:1
26.
Gilbert V. Levin 《Icarus》2002,159(1):266-267
Tsapin et al. (2000, Icarus147, 68-78) propose the strong oxidant ferrate(VI) to explain the Viking Labeled Release Mars life detection results. However, their data do not support that theory. Further, sensitive IR searches for oxidants on Mars found none, and Viking produced physical evidence against an oxidizing surface. Finally, Tsapin et al. (2000, Icarus147, 68-78) report no precautions to prevent microbial contamination from confounding their results. 相似文献
27.
J. Zlotnicki G. Boudon J. P. Viod J. F. Delarue A. Mille F. Brure 《Journal of Volcanology and Geothermal Research》1998,84(1-2)
Self-potential (SP) surveys were made on Mount Pelée volcano (Martinique Island, French West Indies) in 1991 and 1992 in order to recognize its hydrothermal system, the associated groundwater channeling and the main superficial structures of the massif. Almost 70 km of profiles were carried out with an average sample spacing of 50 m. Measurements essentially reveal negative SP anomalies, down to −1700 mV, with high gradients (−1.83 mV/m) due to the infiltration of meteoric water into the massif. Rims of summit calderas Morne Macouba and Etang-Sec present sharp negative SP anomalies on the western, northern, and eastern flanks. Negative SP anomalies indicate no upward water flow beneath Mount Pelée summit. On the southwestern volcano flank, a 3.5×6 km horseshoe-shaped structure corresponding to a southwest flank collapse event, older than 25,000 years BP, is clearly identified by the SP mapping. High gradients border the inner southern rim from Morne Calebasse to St Pierre town and the Caribbean Sea. Along the northern rim of the horseshoe-shaped structure the negative SP anomalies give place to a positive SP anomaly, up to 200 mV, of SW–NE trend. This zone covers the area of two active hot springs (Sources Chaudes and Puits Chaud: 40–65°C). Marine magnetic surveys and bathymetry show that the horseshoe-shaped structure spreads into the Caribbean Sea up to about 10 km from the coast. Buried structural discontinuities are evidenced inside the flank collapse structure. The upper one deviates the groundwater flow coming from the summit toward the south flank where the flow finds an indentation to expand again downwards. This discontinuity is either an old hypothetical caldera rim partly destroyed by the collapse of the south–southwestern flank and covered by recent pyroclastic deposits, or more probably the trace of a bulge landslide. A circulation model of the hydrothermal waters is proposed. Rainfall (5–6 m/year) is partly drained inside the summital calderas and the flank collapse zone through pyroclastic flows down to an impermeable basement. There the groundwater constitutes perched aquifers at the contact of the bulge landslide, or of the hypothetical old caldera rim. Along the inner northern border of the flank collapse structure the phreatic water is reheated. Warm groundwater flows along the northern avalanche structure rim and discharges near the coast in ground and marine outcrops, of medium temperature. Finally, the main part of the meteoric water is channeled along the old caldera rim, or along the bulge landslide towards the south flank of Mount Pelée, where some gaps in the rim exist. There the groundwater finds again a subhorizontal gravitational circulation along Mount Pelée slopes into the Caribbean Sea. 相似文献
28.
A general mixing equation with applications to Icelandic basalts 总被引:4,自引:0,他引:4
Charles H. Langmuir Robert D. Vocke Gilbert N. Hanson Stanley R. Hart 《Earth and Planetary Science Letters》1978,37(3):380-392
The mixing equation applied by Vollmer [1] to Pb and Sr isotope ratios is shown to be a general equation applicable to consideration of element and isotope ratios. The mixing equation is hyperbolic and has the form:Ax + Bxy + Cy + D = 0where the coefficients are dependent on the type of plot considered: i.e. ratio-ratio, ratio-element, or element-element. Careful use of this equation permits testing whether mixing is a viable process, places constraints on end member compositions, allows distinction between mixing of sources and mixing of magmas, and should allow distinction between recent mixing and long-term evolution of sources.The available chemical data for postglacial basalts from Iceland and along the Reykjanes Ridge are not consistent with either mixing of magmas or simple mixing of an enriched ocean island source with a depleted ocean ridge source. If the available analyses for basalts are representative of the source regions, the data are consistent with at least two models neither of which can be properly tested with the available data.(1) There are two separate mixing trends: one beneath Iceland with the alkali basalt source and a depleted Iceland source as end members; the second along the Reykjanes Ridge with a heterogeneous ocean ridge basalt source and a source similar to that for intermediate basalts on Iceland as end members. The depleted Iceland source and the depleted ocean ridge source are not the same.(2) The chemistry of the basalts is not determined by mixing. Instead the basalts are derived from a multiplicity of sources with a similar history which have been isolated for hundreds of millions of years. 相似文献
29.
Major elements can be modelled in ways similar to the quantitative petrogenetic modelling used for trace elements. In contrast to modelling with trace elements, however, modelling with major elements is constrained by the stoichiometry of the solid phases. Within these constraints, the same equations for partial melting and crystallization which have been used to such advantage for trace elements may be used for major elements.Calculated MgO and FeO abundances in a mantle-melt system are used as an example of the modelling technique. Such modelling yields limited fields of permissible melts and residues for a given parent composition, but does not give the paths of melting. It does allow the temperature and extent of melting which gave rise to a melt to be determined from the MgO and FeO abundances of the melt or residual solid. Applying the results of the modelling to igneous rocks and ultramafic nodules leads to the following conclusions, which are subject to the uncertainties in the available distribution coefficients. Least differentiated basalt glasses from the ocean floor are derived from parent melts with less than 15.5 weight % MgO and 8.2 wt. % FeO. Komatiites may be derived by less than 60% melting of a pyrolite source leaving a residue of olivine and pyroxene. Many nodules from the subcontinental mantle appear to be residues of large fractions of melting (>30%) at high temperature and pressure, whereas ultramafic nodules from oceanic basalts appear to be residues of smaller fractions of melting (<30%) at lower temperatures and pressures. 相似文献
30.
Particulate dispersion from sources within a 10- to 13-m tall pine forest was studied experimentally at Brookhaven National Laboratory using stained ragweed pollen and other tracers ranging from 14 to 58 m in size. Forty-seven continuous point source releases lasting from 22 to 55 min were made at heights from 1.75 to 14.0 m from locations having a long fetch through the forest. In most experiments, differently colored ragweed pollen were emitted simultaneously from three locations. In other tests, several particle types were released from a single point. The sampling network consisted of 119 rotoslide samplers at heights from 0.5 to 21.0 m at 57 positions within and at the edge of the forest. Deposition to the ground was sampled by greased microscope slides at each position. Meteorological measurements were taken in and near the forest.Data were classified by particle characteristics, source height and meteorological parameters. Concentration patterns were illustrated on scale diagrams of the sampling grid. Changes in centerline and crosswind integrated concentrations, plume width and height, mass flux, deposition and deposition velocity were studied as a function of distance, particle size and wind speed. Results were compared to those obtained from similar releases over open terrain.In the forest, vertical predominates over lateral dispersion and considerable interchange occurs through the canopy. Flow is channelled somewhat by vegetation density differences but is generally in the direction of the mean wind above the forest. No systematic turning of the wind with height was observed. Most particles are lost to the foliage rather than to the ground and large particles are lost more rapidly than smaller ones. Rate of change in mass flux is similar to that over open terrain and is greater with light than with stronger wind speeds.This research was carried out under the auspices of the New York State Museum and Science Service and the U.S. Atomic Energy Commission (now Energy Research and Development Administration) and was partially supported by Research Grant No. R-800677 from the Division of Meteorology, U.S. Environmental Protection Agency. 相似文献