Transformation of the Ebro River Delta under the Impact of Intense Human-Induced Reduction of Sediment Runoff   总被引：1，自引：0，他引：1  

Mikhailova  M. V. 《Water Resources》2003,30(4):370-378

The regularities of the Ebro River delta formation and the impact of hydraulic construction on the river sediment runoff are discussed. As shown, the drastic reduction of the sediment runoff after the construction of two large reservoirs in the lower river reaches in the 1960s slowed down the delta protrusion and intensified the delta coastline washout.  相似文献   

Fishery Water Releases to the Lower Pool of the Volgograd Hydroelectric Power Plant     

Ratkovich  D. Ya.  Vyruchalkina  T. Yu.  Solomonova  I. V. 《Water Resources》2003,30(4):387-403

Conditions of fish reproduction in the Volga–Caspian Basin depending on the hydrological regime in the Volga lower reaches, transformed by water withdrawals and regulatory impact of reservoirs are considered.  相似文献   

Numerical viscoelastic modelling by the spectral Laguerre method   总被引：1，自引：0，他引：1  

B.G. Mikhailenko  A.A. Mikhailov  G.V. Reshetova 《Geophysical Prospecting》2003,51(1):37-48

Seismic wave propagation in a viscoelastic media can be described by a system of integro-differential equations. The solution of such equations requires special methods when using finite-difference techniques in the time domain. In the frequency domain, the integral terms are represented by complex elastic parameters. This paper presents an efficient algorithm for viscoelastic modelling based on the integral Laguerre transform for the approximation of temporal derivatives and for the calculation of convolution integrals. For the calculation of spatial derivatives, it is possible to use various methods: finite-difference and finite-element techniques, spectral and pseudo-spectral methods. We then obtain a system of algebraic equations with a matrix independent of the parameter m , i.e. the degree of the Laguerre polynomials. In this case, only the right-hand side of the system has recurrent dependence on the parameter m , which is an analogue of the temporal frequency in the frequency domain. The obtained system with a large number of right-hand sides can be solved using fast methods, where the matrix is transformed only once, as opposed to the frequency-domain approach, when the matrix is transformed for each temporal frequency.  相似文献   

3D F–K and finite-difference dip moveout in cross-spreads     

Andrey V. Masjukov 《Geophysical Prospecting》2003,51(4):333-345

A 3D F–K dip-moveout (DMO) is developed, which is applicable to data acquired in an elementary single-fold cross-spread. The key idea is that a 3D log-stretch transform and the inherent regularity of the cross-spread geometry make it possible to transform 3D Fourier DMO. The derived theory generalizes the 2D Fourier shot-gather DMO in the log-stretch domain; 2D turns out to be a special case. Similarly to 2D, the cross-spread DMO becomes convolutional after multidimensional logarithmic stretch. The proposed method works for orthogonal and slanted acquisition geometries; the cross-spread DMO relationships are found to be independent of the intersection angle of the shot and receiver lines. In contrast to integral (Kirchhoff-style) methods, the cross-spread F–K DMO does not degrade from the inevitable irregularity in 3D sampling of offsets in a CMP gather. The newly derived F–K DMO operator can be approximated by finite-difference (FD) schemes; the low-order FD cross-spread DMO equation is shown to be the 3D extension of the Bolondi and Rocca offset continuation. It is shown that F–K and low-order FD operators are effective in a synthetic case.  相似文献   

An Environmentally Friendly Decontamination Protocol for Ground Water Sampling Devices     

Louise V. Parker  Thomas A. Ranney 《Ground Water Monitoring & Remediation》2003,23(2):84-91

Several detergent-washing/air-drying decontamination protocols were tested to determine their ability to remove residual contamination from two types of ground water sampling devices. We tested a relatively simply constructed device, a bailer, and a much more complex, and theoretically more difficult to decontaminate, bladder pump. The devices were decontaminated after sampling ground water that was contaminated with organics that varied in their hydrophobic nature and propensity to be sorbed by the materials in the devices. These studies showed that a hot-detergent wash, hot-water rinse, and hot-air drying protocol was effective.  相似文献   

A quantitative study of the energy release in the aftershocks of the Bhuj earthquake, 2001, India, using Lg phase     

G. Jayachandran  M.M. Abdul RazakA.G.V. Prasad  E. Unnikrishnan 《Physics of the Earth and Planetary Interiors》2003,138(2):131-145

The devastating earthquake on 26 January 2001 at Bhuj, India, resulted in large-scale death and destruction of properties of several million US dollars. The moment magnitude of the earthquake was 7.7 and its maximum focal intensity exceeded X in MM scale. The rate of aftershocks of this earthquake, recorded at Gauribidanur seismic array station (GBA), shows a monotonic decay with time superposed with oscillations. For the Indian continent the Lg phase is a prominent arrival at regional distances. The estimate of Lg amplitude is obtained by optimally fitting the Lg wave train to a exponential decay curve. The logarithm of these amplitudes and logarithm of root mean square (rms) value of actual amplitudes of the Lg are calibrated with USGS m_b to create a local m_bLg magnitude scale. The energy released from these aftershocks is calculated from the rms value of Lg phase. The plot of cumulative energy release with time follows the power law of the form t^p, superposed with oscillations. The exponent of the power law, p, is estimated both by a time-window scanning method and by an interpolation method. The value of p is 0.434 for time-window scanning method and 0.432 for the interpolation method. The predominant periods found in the oscillatory part of the cumulative energy, obtained by differencing the observed from the power law fit, are 10.6, 7.9, 5.4, 4.6 and 3.5 h for time-window scanning method. The corresponding periods for interpolation method are 13.4, 11.5, 7.4, 4.2, 3.5, 2.6 and 2.4 h.  相似文献   

Weathering control over geomorphology of supermature Proterozoic Delhi quartzites of India     

Jayant K. Tripathi  V. Rajamani 《地球表面变化过程与地形》2003,28(13):1379-1387

Quartz and quartzite are thought to be resistant as a mineral and a rock respectively; however, we have shown that the presence of small amounts of pyrite in the quartzites makes them vulnerable to weathering. We observe that weathering of Proterozoic quartzite in the semi‐arid conditions around Delhi proceeded from fractures towards the inside and produced weathering rinds. The chemical index of alteration (CIA), which is actually a measure of weathering of aluminosilicate minerals, increases from the core outwards, through the rinds. Although aluminosilicate minerals occur only as minor phases (<2 per cent), their weathering indicates a movement of the weathering front from the periphery towards the core. We have suggested a coupled mechanism in which the dissolution of pyrites by moving water produced a sulphate‐bearing acidic solution and ferrous iron, which reacted with aluminosilicate minerals and quartz, respectively. This initially makes the Delhi quartzite porous and subsequently friable. The total disintegration of grain to grain contacts imparted friability to this quartzite to produce silica sand. Subsequent physical erosion of loose sand, produced during rind development in the outermost zones, has given rise to features like tors, spheroids, gullies, cavities and small‐scale caves on these quartzites. Thus, the terrain has acquired ruggedness in semi‐arid conditions. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Model Tests and Field Experiments for Fragmentation Assessment During Ringhole Blasting in BG Panels     

C. Sawmliana  P. Pal Roy  V. M. S. R. Murthy 《Fragblast: International Journal for Blasting and Fragmentation》2003,7(4):257-268

Experimental blasts were conducted in concrete blocks of known strengths to correlate field results in Blasting Gallery (BG) panels of GDK-10 Incline for improving fragmentation of coal to an optimum level so that blasted coal could easily be lifted totally by remote controlled LHDs and thereby mitigating the possibility of occurrence of spontaneous heating in BG districts before exhaustion of the panel. Various charge loading parameters and consequent breakage results were critically analyzed to arrive at a constructive conclusion, which could satisfactory improve the blast results.  相似文献   

Local site effects in Latur, India: an empirical study based on the aftershocks of the Killari earthquake of September 29, 1993     

V. Midzi  D. D. Singh  K. Atakan  J. Havskov 《Engineering Geology》2003,68(3-4):251-258

The site amplification is estimated at five seismic stations of the Latur region using the horizontal to vertical spectral ratios of 33 aftershocks of the main Killari earthquake of September 29, 1993 (UTC). Spectral amplifications, ranging from a factor of 2–6 are found to vary with frequency at different places. Significant amplification is found at four sites within the Latur region, at Basavakalyan, Kasgi, Killari, and Mudgad Eakoji villages. Our results show a positive correlation between the site amplification and the damage pattern in area. The pattern and the nature of the site amplification estimated in the present study corroborates also with the analytical models and the borehole data indicating alternating layers of unconsolidated sediments and basaltic rocks.  相似文献   

Influence of accretion-disk models on the structure of the Iron Κ<Subscript>α</Subscript> line     

A. F. Zakharov  S. V. Repin 《Astronomy Reports》2003,47(9):733-739

Broad iron Κ_α emission with a characteristic two-peaked profile is observed in most Seyfert galaxies in the X-ray. We have calculated the profiles of such lines emitted by an accretion disk in a Schwartzschild metric. The dependence of the temperature distribution in the disk on the line shape is demonstrated. All the calculations include general relativistic effects. The disk material is assumed to move in circular geodesics in the equatorial plane. The line profile is extremely complex, even in a traditional model for the radial temperature distribution, complicating interpretation of the observational data.  相似文献