Landslides - Outburst flooding after a landslide dam breach causes global fatalities and devastation. Information on the timing, magnitude, and location of the landslide dam is crucial to hazard... 相似文献
The devastating damage after the 1999 Chi-Chi and 1999 Izmit earthquakes has greatly motivated soil–reverse fault interaction studies. However, most centrifuge modeling studies have employed a single homogeneous soil layer during testing, which does not represent in situ conditions. Indeed, while geological conditions vary spatially, engineering soils are often underlain by soft rocks. Therefore, four centrifuge models were developed to evaluate the effect of soft rock layers on the ground surface and subsurface deformation. Sand–cement mixtures of varying thicknesses with a uniaxial compressive strength of 0.975 MPa, simulating extremely soft rock, were overlain by pluviated sandy soil. The model thickness was 100 mm, corresponding to 8 m in the prototype scale when spun at 80 g. Every model was subjected to a vertical offset of 50 mm/4 m (0.5 H; H: total sedimentary deposit thickness) along a reverse fault with a 60° dip. The results indicate that the presence of a soft rock stratum results in the creation of a horst profile at the ground surface. Additionally, the thinner the soil layer on top of the soft rock stratum is, the longer and higher the horst created at the ground surface. Consequently, the fault deformation zone lengthens proportionally with the increasing thickness ratio of the soft rock. Furthermore, the presence of soft rock as an intermediary stratum between bedrock and soil causes the deformation zone boundary on the hanging wall side to move in the direction of fault movement.
A new pattern-recognition algorithm detects approximately 90% of the mines hidden in the Coastal Systems Station Sonar0, 1, and 3 databases of cluttered acoustic images, with about 10% false alarms. Similar to other approaches, the algorithm presented here includes processing the images with an adaptive Wiener filter (the degree of smoothing depends on the signal strength in a local neighborhood) to remove noise without destroying the structural information in the mine shapes, followed by a two-dimensional FIR filter designed to suppress noise and clutter, while enhancing the target signature. A double peak pattern is produced as the FIR filter passes over mine highlight and shadow regions. Although the location, size, and orientation of this pattern within a region of the image can vary, features derived from higher order spectra (HOS) are invariant to translation, rotation, and scaling, while capturing the spatial correlations of mine-like objects. Classification accuracy is improved by combining features based on geometrical properties of the filter output with features based on HOS. The highest accuracy is obtained by fusing classification based on bispectral features with classification based on trispectral features. 相似文献
Field infiltration tests using portable rainfall infiltrometers were conducted in the Wangjiagou experimental basin in the hilly loess region of north China. Based on data collected at 27 sites, a topographic zonation of infiltration characteristics was observed. The average steady infiltration rate and the average ponding time decreased from the hilltop to the hillslope and further decreased to the gully wall. Such a zonation is closely related to the variations of topography, soil and land use conditions in the study area. A general infiltration model is proposed. Collected field data are used to establish the applicability of the proposed model in the study area. 相似文献
A direct method of parameter identification for a fracture porous medium can be formulated. The coefficient of piezo-conductivity and the virtual fracture transmissivity can be determined using a combination of graphical methods and approximate formulae. Field calculation provides a practical demonstration of the proposed approach. 相似文献
The laboratory characterization of a field-operable surface-enhanced Raman scattering sensor (SERS optode) is presented for the detection of aromatic hydrocarbons in seawater. The sensor has been developed for deployment with a robust underwater spectrograph. To meet the demands of the harsh seawater application, sol-gel derived SERS substrates were used. The calibration curves of six PAHs were determined to be of Langmuir adsorption isotherm type with limits of detection ranging from the microg l(-1) to ng l(-1) level. The experimentally determined adsorption constants varied strongly with the molecular weight of the analytes and correlated with their solubility. A mixture of five PAHs dissolved in seawater was investigated to demonstrate the utility of this method for screening. Emphasis was put on the interference from suspended particulate matter (SPM). The Raman measurement with backscattering configuration was shown to be immune against turbidities up to 1000 NTU. The physico-chemical interference arising from adsorption by the sediment was measured on-line by adding sediment to a PAH-spiked solution. According to the calibration curve, the PAH concentration decrease corresponded to more than 98% of the analyte being scavenged by the sediment. 相似文献
Fine-resolution regional climate simulations of tropical cyclones (TCs) are performed over the eastern Australian region. The horizontal resolution (30 km) is fine enough that a good climatological simulation of observed tropical cyclone formation is obtained using the observed tropical cyclone lower wind speed threshold (17 m s–1). This simulation is performed without the insertion of artificial vortices (bogussing). The simulated occurrence of cyclones, measured in numbers of days of cyclone activity, is slightly greater than observed. While the model-simulated distribution of central pressures resembles that observed, simulated wind speeds are generally rather lower, due to weaker than observed pressure gradients close to the centres of the simulated storms. Simulations of the effect of climate change are performed. Under enhanced greenhouse conditions, simulated numbers of TCs do not change very much compared with those simulated for the current climate, nor do regions of occurrence. There is a 56% increase in the number of simulated storms with maximum winds greater than 30 m s–1 (alternatively, a 26% increase in the number of storms with central pressures less than 970 hPa). In addition, there is an increase in the number of intense storms simulated south of 30°S. This increase in simulated maximum storm intensity is consistent with previous studies of the impact of climate change on tropical cyclone wind speeds. 相似文献
The stability of biomass-derived black carbon (BC) or biochar as a slow cycling pool in the global C cycle is an important property and is likely governed by environmental conditions. This study investigated the effects of water regimes (saturated, unsaturated and alternating saturated–unsaturated conditions) and differences in BC materials, produced by carbonizing corn residues and oak wood at two temperatures (350 °C and 600 °C) on BC degradation at 30 °C over 1 year in a full factorial experiment. Effects of water regime on C loss and potential cation exchange capacity (CECp at pH 7) significantly depended on biomass type. Corn BC was both mineralized (16% C loss for the first year) and was oxidized [1000 mmole(+) kg?1 C] significantly faster under unsaturated conditions than under other water regimes, whereas oak BC mineralized most rapidly (12%) under alternating saturated–unsaturated conditions with similar oxidation, irrespective of water regime. Over 1 year of saturated incubation, the O/C ratio values did not significantly (P > 0.05) increase even though BC was mineralized by 9% and CECp increased by 170 mmole(+) kg?1 C, in contrast to unsaturated and alternating saturated–unsaturated conditions. While mineralization and oxidation significantly decreased at higher charring temperature for corn, no difference was observed for oak (P > 0.05). Unsaturated and alternating conditions increased carboxylic and OH functional groups, while they decreased aliphatic groups. The pH increased by about one unit for corn BC, but decreased by 0.2 units for oak BC, indicating strong mineral dissolution of corn BC. Carbon loss strongly correlated with changes in O/C values of both corn BC and oak BC, indicating that oxidation of BC was most likely the major mechanism controlling its stability. However, under saturated conditions, additional mechanisms may govern BC degradation and require further investigation. 相似文献
Geomagnetism and Aeronomy - Homogeneous series of solar cosmic-ray events for four solar-activity cycles against the background of decreased activity in cycles 23 and 24 are considered. The number... 相似文献