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1.
This paper presents a second-order work analysis in application to geotechnical problems by using a novel effective multiscale approach. To abandon complicated equations involved in conventional phenomenological models, this multiscale approach employs a micromechanically-based formulation, in which only four parameters are involved. The multiscale approach makes it possible a coupling of the finite element method (FEM) and the micromechanically-based model. The FEM is used to solve the boundary value problem (BVP) while the micromechanically-based model is utilized at the Gauss point of the FEM. Then, the multiscale approach is used to simulate a three-dimensional triaxial test and a plain-strain footing. On the basis of the simulations, material instabilities are analyzed at both mesoscale and global scale. The second-order work criterion is then used to analyze the numerical results. It opens a road to interpret and understand the micromechanisms hiding behind the occurrence of failure in geotechnical issues. 相似文献
2.
We present a computer model calculation for the racemization of a possible excess of amino acids in the icy fraction of comet nuclei bring about by ionizing radiation released during the decay of26Al,40K,235U,238U and232Th. The model takes into account a total of 110 chemical reactions, of which 91 are needed to explain the radiation chemical processing of the major constituents of comet nuclei (Navarro-Gonzálezet al., 1992) and 19 are necessary to simulate the radiolysis of glycine/alanine mixtures in aqueous solutions (Navarro-Gonzálezet al., 1994 and 1996). It is predicted that an enantiomeric excess of alanine would not be destroyed by radioracemization during the decay of embedded radionuclides. Nevertheless, this enantiomeric excess could be attenuated by the formation of racemic amino acids in the interior of comet nuclei as a result of the radiation-induced polymerization of HCN. 相似文献
3.
Yannick Giraud-Héraud Jean Kaplan François De Volnay Martin Charling Tao Sylvaine Turck-Chièze 《Solar physics》1990,128(1):21-33
The Saclay solar evolution code is used to check the effect of WIMPs on solar evolution. In this paper we study the effects of various types of Cosmion-matter interactions, give constraints on the crosssections compatible with the measured neutrino rate of 2 SNU on chlorine, and relate these constraints to ongoing dark matter detection experiments.Unité associée au CNRS UA 280, F-75251 Paris Cedex 05, France.On leave from LPC, Collège de France. 相似文献
4.
Gérard Daigne Patrick Charlot Christine Ducourant Jean-François Lestrade 《Astrophysics and Space Science》2003,286(1-2):255-260
The question of positioning the optical counterparts of the ICRF quasars is outlined in the perspective of future space astrometry
missions, which ultimately will bring a new realization of the ICRS in the optical range. Ground-based interferometry with
a dual-field observing mode (PRIMA/VLTI),together with the missions DIVA and FAME, will have a key role in building an extragalactic
reference frame in the optical/near-IR range with about the same accuracy as that of the present (VLBI) primary frame.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
To emphasize the rotational effects of a simple friction between colliding bodies in a keplerian field we investigate numerically the evolution of the rotational energies in a three dimensional system of spherical particles interacting through inelastic collisions in a deterministic model. All the particles are made of the same material but they possibly have different sizes. Each collision reduces the relative surface velocity and there are exchanges between orbital energy and rotational energy. Our results are compared with some previous papers and our aim is to supply other probabilists models with simple basic references about mean dynamical properties.The rotational energy of the colliding bodies tends to reach an equilibrium state that depends only on the rate of energy loss in the collision process. Internal rotations prevent the complete flattening of the system. With this model, light and small particles spin faster than the massive and big ones. We observe an excess of prograde rotations on counterclockwise orbits. The ratio of rotational and orbital energies is % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaaBa% aaleaacaWGYbaabeaakiaac+cacaWGfbWaaSbaaSqaaiaadUgaaeqa% aOGaeyisISRaaGymaiaaicdadaahaaWcbeqaaiabgkHiTiaaiodaaa% aaaa!3F83!\[E_r /E_k \approx 10^{ - 3} \] while the ratio of corresponding mean angular velocities is % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaaWaaeaacq% aHjpWDaiaawMYicaGLQmcacaGGVaWaaaWaaeaacqGHPoWvaiaawMYi% caGLQmcacqGHijYUcaaIYaaaaa!4008!\[\left\langle \omega \right\rangle /\left\langle \Omega \right\rangle \approx 2\] These values depends strongly on the dimensional scale of the model. 相似文献
6.
There exist a number of landslides along the north Anatolian fault zone (NAFZ) between Tasova and Alparslan in Amasya province
in Turkey. These landslides extending over an area of 2.5 × 6.0 km are triggered by steepening of slopes due to undercutting
by the Yesilirmak River and groundwater fluctuations. The landslides have affected 30 buildings in the western part of Tasova.
In this study, in order to investigate the engineering geological characteristics of the landslides and their environmental
impacts, representative samples from geological units were collected and a total of six boreholes were drilled. Plastic pipes
were installed into the boreholes to measure the groundwater fluctuations and to determine the position of the sliding surface.
For a two-year monitoring period, using a GPS linked to a fixed station system, the magnitude of the movements ranged between
11.7 and 17.6 cm at the toe of landslide. The landslides that occurred in the study area were in the form of retrogressive
circular and multiple circular failures. The factor of safety along a number of cross-sections calculated by the limit-equilibrium
method of analysis is 0.96 in static condition. After further analyses, construction of a toe buttress with surface drainage
may be suggested as a remedial measure to minimize the effects of these landslides. 相似文献
7.
Marie-Françoise André Samuel Etienne Denis Mercier Franck Vautier Olivier Voldoire 《Environmental Geology》2008,56(3-4):677-688
A first application of geomorphological methods to the assessment of sandstone deterioration at Angkor is presented. Damage diagnosis was carried out on the first eastern tier of the central pyramid of the 1,000 year-old Ta Keo temple. Methods combine field observations and measurements at 230 sampling points, high-resolution lasergrammetry and stereophotogrammetry on a 2-m2 test zone, and SEM observations. The first results indicate that decay operates through a synergistic combination of weathering phenomena dominated by scaling and solution, and exhibits a high spatial variability. Percentages of deteriorated surfaces vary from 17.6 to 93.8%, and average stone recession values from 0.00 to 2.71 cm (minimum) and 0.34 to 5.49 cm (maximum). On the test-zone, stereophotogrammetry and 3D-mapping of the present and reconstructed initial states using lasergrammetry indicate that erosion scars up to 6 cm deep have formed since 1963. On the whole, the amount of deteriorated surfaces more than tripled between 1963 and 2008. The degree of implication of salts in stone decay remains unclear for most efflorescences are composed of calcite (CaCO3), with secondary importance of barite (BaSO4) and gypsum (CaSO4·2H2O). Future prospects aim to evaluate the impact on stone decay of the clearing out of the temple from the forest in the 1920s. 相似文献
8.
Oleg Zaytsev Rafael Cervantes-Duarte Orzo Montante Artemio Gallegos-Garcia 《Journal of Oceanography》2003,59(4):489-502
High primary productivity on the Pacific coast of the Baja California Peninsula is usually related to coastal upwelling activity
that injects nutrients into the euphotic zone in response to prevailing longshore winds (from the northwest to north). The
upwelling process has maximum intensity from April to June, with the coastal upwelling index varying from 50 to 300 m3/s per 100 m of coastline. Along the entire coast of the peninsula, the upwelling intensity changes in accordance with local
wind conditions and bottom topography. Spatial variability can also be modulated by the influence of mesoscale meanders of
the California Current. We have identified the seasonal and synoptic variability of upwelling signatures on the Baja California
shelf, using averaged monthly and weekly sea surface temperature (SST) distributions obtained from remote sensing imagery
from the Advanced Very High Resolution Radiometer in the period from 1996 to 2001. Analysis of SST distribution and direct
experimental data on temperature and nutrient concentration shows that the areas with the coldest SST anomalies were closely
related to the bottom slope, shelf width, and coastline orientation relating to wind direction. We also assume that the nutrient
transport into the coastal lagoons may be forced by the coupling of coastal upwelling and tidal pumping of surface waters
into the lagoon system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Rita Borges Radhouan Ben-Hamadou M. Alexandra Chícharo Pedro R Emanuel J. Gonalves 《Estuarine, Coastal and Shelf Science》2007,71(3-4):412-428
There have been no previous studies of the composition of nearshore larval fish assemblages along the coast of Portugal. We aimed to describe the composition and horizontal distribution patterns of larval fish assemblages and their temporal dynamics near a rocky reef at depths shallower than 13 m (inshore) and at two miles (3.70 km) from shore (offshore), as well as along transects perpendicular to the shoreline, from the reef to 10 miles offshore (18.52 km). Samples were taken using 5 min sub-surface trawls at the rocky shore of the Arrábida Marine Park (W Portugal). A total of 1021 larvae were collected, belonging to 61 taxa inshore and to 29 taxa offshore. Along transects, 626 larvae of 52 taxa were collected. Most larvae belonged to coastal species associated with rocky reefs. Total larval abundance and diversity were higher from May to July, which is consistent with the spawning activity of adults. Diversity and total larval abundance decreased significantly with increasing distance from shore, both in the inshore/offshore comparison and in the transects, where this decrease was evident at a very small spatial scale (within the first mile from the reef). Species assemblages differed in the pattern of distribution, with most species clearly associated to the extreme nearshore. The distribution patterns obtained were independent of the spawning mode of species. Results are discussed in the light of the possible physical mechanisms that can potentially act at the Arrábida Marine Park to facilitate larvae retention and the role of larval behaviour. 相似文献
10.
Abstract. Rhodoliths provide a stable and three-dimensional habitat to which other seaweeds and invertebrates can attach. Although ecological factors affecting rhodolith beds have been studied, little is known about the effect of rhodolith species and growth-form on associated fauna. Experiments were conducted at three rhodolith beds in the central-west Gulf of California. Faunal abundance differed significantly in relation to rhodolith-forming species, but no significant differences were observed between different growth-forms. Rhodolith structure differs between the species Lithophyllum margaritae and Neogoniolithon trichotomum , and the combination of structure differences and rhodolith abundances may be responsible of the significant differences in faunal abundance and richness. Crustaceans, polychaetes and molluscs were the most important taxa in all three rhodolith beds. The amphipod species Pontogeneia nasa and the cnidarian Aiptasia sp. were dominant in both rhodolith beds, El Requesón and Isla Coyote, in Bahía Concepción. The Isla Coronados rhodolith bed was dominated by an unidentified harpacticoid copepod (Copepoda sp.1). Rhodolith species is more important than growth-form in determining abundance and richness of the associated fauna. Nevertheless, factors such as wave motion, depth, bioturbation and others should be considered when studying organisms associated with rhodolith beds. 相似文献