The design of a drainage system for a roofing slate quarry was implemented by the enhancement of discharge peak estimation, and the uncertainty inevitably associated with the engineering model was reduced.
The development of a topographical, geological, and vegetation cover database developed from a Geographical Information System (GIS) allowed for the definition of the drainage network for a hydraulic system, along with the calculation of the runoff coefficient. This is applied to the digital model of accumulated flow (DMF) as a weight correction coefficient, using a matrix-based model at 5×5 m resolution. The new digital model of corrected accumulated flow (DMCF) is the result of combining the thematic maps with the map of slope <3%, which was previously created from the slope model. It is demonstrated that this new model allows to apply the “Rational Method” on cartographic units defined by the GIS.
The DMCF is compared with other traditional applications of the Rational Method based on the calculation of the discharge peak considering: (1) the drainage basin as a single watershed or (2) defining an average runoff coefficient in each sub-watershed. Both approaches have bigger discharge peaks than those obtained by the DMCF since the slope, lithology, and vegetation cover have average values, and the runoff coefficient is poorly defined, increasing the uncertainty in the discharge peak. 相似文献
A geometrical structure is imposed on compositional data by physical and chemical laws, principally mass conservation. Therefore, statistical or mathematical investigation of possible relations between data values and such laws must be consistent with this structure. This demands that geometrical concepts, such as points that specify both mass and composition in linear space, and lines in projective space that specify composition only, be clearly defined and consistent with mass conservation. Mass thus becomes the norm in composition space in place of the Euclidean norm of ordinary space. Coordinate transformations inconsistent with this geometry are accordingly unnatural and misleading. They are also unnecessary because correlation arising from the constant mass presents no unusual difficulty in the analysis of the underlying quadratic form. 相似文献
An 11 million year long record of the Oligocene geomagnetic field has been obtained from pelagic sediments of DSDP Hole 522 An average sample spacing of 4 cm yielded approximately one specimen per 4 to 8 kyr. The rock magnetics are remarkabh consistent across the entire interval. Previous work demonstrated a magnetic mineralogy dominated by magnetically stable magnetite. The natural remanent magnetism (NRM) carries an Oligocene polarity timescale that is in excellent agreement with the Oligocene reversal record as determined from marine magnetic anomalies (MMAs), including many of the so-called 'crypto-chrons'. Normalized NRM intensities from the undisturbed portions of the record yield a time series of variations with features consistent with a number of other palaeointensity time series derived from both sedimentary and lava sequences. These features include consistent, major decreases in palaeointensity (DIPs) at reversal boundaries, and occasional DIPs between reversal boundaries that could correspond to lineated 'tiny wiggles' in the MMA records. The data set suggests that the overall field strength was 40 per cent higher in the first half of the Oligocene when the average reversal frequency was 1.6 Myr-1 than in the second half when the reversal frequency was 4 Myr-1. There is also a weak dependence of average field strength on length of polarity interval. Finally, in the three cores suited to spectral analysis (of coherent polarity and relative intensity independent of lithological contamination), there is a persistent ca. 30–50ka periodicity in the variations of the relative intensity, suggesting that the geomagnetic field 'pulses' at about this frequency, not only during the Brunhes (as demonstrated by Tauxe & Shackleton 1994), but in the Oligocene as well. 相似文献
The geomagnetic field intensity during Archaean times is evaluated from a palaeomagnetic and chronological study of a dolerite dyke intruded into the 3000 Ma Nuuk Gneisses at Nuuk (64.2°N, 51.7°W), west Greenland. Plagioclase from the dolerite dyke yields a mean K-Ar age of 2752 Ma. Palaeomagnetic directions after thermal demagnetization of the dyke and the gneiss reveal a positive baked-contact test, indicating that the high-temperature-component magnetization of the dyke is primary. Thellier experiments on 12 dyke specimens yield a palaeointensity value of 13.5±4.4 μT. The virtual dipole moment at ca. 2.8 Ga is 1.9±0.6 × 1022 Am2, which is about one-quarter of the present value. The present study and other available data imply that the Earth's magnetic field at 2.7 ∼ 2.8 Ga was characterized by a weak dipole moment and that a fairly strong geomagnetic field similar to the present intensity followed the weak field after ca. 2.6 Ga. 相似文献
We studied the existence of dynamical stochastic relations in the evolution of the am index. A first analysis of the autocorrelation functions showed evidence of several seasonalities. We first used linear (ARMA) models, and it was found that these do not account for the whole internal dynamics of the data series. We then used various non-linear models to provide a better fit to reality. The forecast performances of the non-linear models are not significantly different from those of the linear model. We give a tentative explanation for the failure of the non-linear predictions. Finally, ARCH models were used in order to take into account the fact that the confidence interval for the predicted value depends on past observations. 相似文献