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941.
任基 《成都信息工程学院学报》1990,(1)
本文介绍了一种新的标定流气式正比计数管的方法。此方法的特点是把正比管作为吸收体,利用He气对光子较为透明的原理,标定正比管的探测效率。方法简便实用,并对P-10(90%Ar+10%CH_4)为工作气体的正比管进行了标定。 相似文献
942.
943.
Lies Loncke Virginie Gaullier Laurence Droz Emmanuelle Ducassou Sébastien Migeon Jean Mascle 《Marine and Petroleum Geology》2009,26(5):633-646
The Nile deep-sea fan (NDSF), turbiditic system reaching a size of about 90,000 km2, has been investigated since 1998 by several geophysical methods (multibeam bathymetry, backscatter imagery, seismic data, 3–5 kHz echo-sounding). The analysis of this important data set evidenced that the NDSF is the locus of numerous multi-scale slope instabilities. Three main types of instabilities have been defined, mainly on the basis of their size or origin. (1) First type of instabilities related to the generalized gravity spreading of the Plio-Quaternary deep-sea fan on Messinian salt layers. This global spreading is accommodated by numerous localized slides. (2) Second type of instabilities correspond to giant mass movements probably triggered either by earthquakes, fluids, or climate and eustatic oscillations. Finally, (3) third type of instabilities correspond either to localized levee liquefactions or to thin-skinned slides on the steep slopes of the Eratosthenes seamount. The deposits generated by these slope movements greatly participate in the building of the NDSF. The characterization of these different instabilities, in a petroleum province as the NDSF, has important implications in terms of risk assessments when considering drilling operations. 相似文献
944.
Artificial neural networks are used to predict the micro‐properties of particle flow code in three dimensions (PFC3D) models needed to reproduce macro‐properties of cylindrical rock samples in uniaxial compression tests. Data for the training and verification of the networks were obtained by running a large number of PFC3D models and observing the resulting macro‐properties. Four artificial networks based on two different architectures were used. The networks used different numbers of input parameters to predict the micro‐properties. Multi‐layer perceptron networks using Young's modulus, Poisson's ratio, uniaxial compressive strength, model particle resolution and the maximum‐to‐minimum particle ratio showed excellent performance in both training and verification. Adding one more variable—namely, minimum particle radius—showed degrading performance. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
945.
Félix Darve Stein Sture René de Borst Andrew J. Whittle Ian M. Smith 《国际地质力学数值与分析法杂志》2009,33(3):n\a-n\a
946.
Joaquín Tintoré Raúl Medina Lluís Gómez-Pujol Alejandro Orfila Guillermo Vizoso 《Ocean & Coastal Management》2009,52(10):493-505
Coastal zones and beach management practices, regulatory decisions, and land use planning activities along coastal zones have historically been made with insufficient information concerning the dynamic coastal environment. In this study we address and integrate an interdisciplinary scientific approach to Coastal Management in a scenario where lack of this information has resulted in the alteration of the natural dune system of the beach of Cala Millor (Mallorca, Balearic Islands, Spain), and also in the perception of the beach retreat and in a parallel way, a risk for the tourism resources. In this work the detailed studies on beach morphodynamics have been developed as a basis for integrating proper beach management, beach natural dynamics and local users and economic agent interests. From this point of view a set of solutions are considered as the basis for a management policy that links beach science and beach use as a tourism resort resource. 相似文献
947.
948.
This modelling study deals with the time‐dependent behaviour of rockfill media, which is of particular interest during the life of rockfill dams. Breakage of rock blocks and crack propagation are the main processes responsible for rockfill creep and collapse. The modelling procedure presented here is performed on two scales: on the rock block scale, where the grain is taken to be an assembly of rigid particles initially endowed with cohesive bonds, and on the rockfill scale, which is taken to involve a set of breakable grains interacting via contact and friction processes. The grain breakage process is described in term of a thermodynamically consistent damage interface model, where the damage is a gradual delayed process. This model was implemented in a non‐smooth contact dynamics code. The effects of the main parameters involved were analysed by performing numerical studies. The ability of the model to predict the creep behaviour of rockfill media is confirmed by presenting several simulations. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
949.
P. Schmidt-Thomé 《International Journal of Earth Sciences》1943,33(4-6):446-473
Ohne Zusammenfassung 相似文献
950.