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排序方式: 共有274条查询结果,搜索用时 15 毫秒
121.
Ali Kafaei Mohammadnejad Seyyed Mohammad Mousavi Mohammad Torabi Mehdi Mousavi Amir Hossein Alavi 《Environmental Earth Sciences》2012,67(1):53-70
This study presents new attenuation models for the estimation of peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground displacement (PGD) using a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The PGA, PGV, and PGD were formulated in terms of earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms. A worldwide database of strong ground motions released by Pacific Earthquake Engineering Research Center (PEER) was employed to establish the models. A traditional genetic programming analysis was performed to benchmark the proposed models. For more validity verification, the GP/SA models were employed to predict the ground-motion parameters of the Iranian plateau earthquakes. Sensitivity and parametric analyses were carried out and discussed. The results show that the GP/SA attenuation models can offer precise and efficient solutions for the prediction of estimates of the peak time-domain characteristics of strong ground motions. The performance of the proposed models is better than or comparable with the attenuation relationships found in the literature. 相似文献
122.
Consider the problem of estimating the Quasar Luminosity Function (QLF). In a 2007 Ph.D. dissertation, Hugeback considers the QLF as a nonhomogeneous poisson process and estimates the intensity function under SDSS DR3 data (The University of Chicago, AAT 3273021). The present study follows Hugeback’s approach but introduces a mixture component which improves Hugeback’s model in several respects. Namely, the database is partitioned into two groups according to redshift: z < 2.75 and z ? 2.75. Next, a mixture model for the QLF was derived using the concept of pseudolikelihood, the addition of a K function to allow for inter-point interaction, and evaluation of residuals diagnostic plots. This mixture model (i) improves the deviance of Hugeback’s model, and (ii) satisfies residual assumptions that are violated under Hugeback’s model. Moreover, this study confirms Hugeback’s finding of inhomogeneity in the QLF, and provides stronger evidence for the existence of an interaction between redshift and absolute magnitude. 相似文献
123.
Laboratory experiments of tsunami run-up and withdrawal in patchy coastal forest on a steep beach 总被引:1,自引:0,他引:1
Jennifer L. Irish Robert Weiss Yongqian Yang Youn Kyung Song Amir Zainali Roberto Marivela-Colmenarejo 《Natural Hazards》2014,74(3):1933-1949
Laboratory experiments were carried out to study tsunami flow dynamics in the presence of patchy macro-roughness, representing coastal forest, on a 1:10 steep beach. The experimental setup included four cross-shore rows of roughness patches affixed to the dry beach in a staggered array, such that 12 % of the staggered array region had higher roughness. The flow field during run-up and withdrawal was quantified using point measurements of velocity and flow depth at 20 locations, while high-resolution video was used to track bore position during run-up. Data analysis revealed that while inundated area was marginally impacted when patchy roughness was present, flow depths and flow force were, respectively, increased by more than 40 and 30 % in some areas within the patch array; a decrease in flow force was also observed in some areas. Alongshore variation in flow depth, induced by the roughness patches, was most pronounced during withdrawal. These findings suggest that patchy macro-roughness, like that created by coastal forest, will simultaneously lead to increased protection in some areas and decreased protection in others. 相似文献
124.
Amir Barzegari Nasser Madani Esfahani Omid Asghari 《Arabian Journal of Geosciences》2014,7(8):2991-3010
Geostatistical simulations have been recently widely used in the geological and mining investigations. Variogram, the fundamental tools of geostatistics, can identify the spatial distribution of the regionalized variable within the area. One of the important issues of geostatistical simulation in seismotectonics is producing uncertainty maps, which could be applicable to predict earthquake parameters through the site locations especially for civil structures like bridges. It can help engineers to design the structure of interest better. Earthquake parameters as for example seismic fault and surface wave magnitude (Ms) have significant impact on the feasibility study of the civil structures. In this research, a method is presented to produce uncertainty maps for seismic fault and surface wave magnitude, Ms. For this aim, information related to surface wave magnitude and fault trace in Zagros region (SW of Iran) has been collected. Then, the relationships between them through the site location have been investigated and analyzed by conditional geostatistical simulation. In order to quantify the uncertainty of each parameter, the uncertainty formula after generating the E-type maps has been provided and discussed. Finally, in “Talgah Bridge” site, these uncertainty maps were produced to interpret the impact of the surface wave magnitude and fault trace in this specific civil structure. 相似文献
125.
Amir Houshang Ehsani 《Arabian Journal of Geosciences》2014,7(4):1659-1670
In this paper, we propose a semiautomatic method for landscape analysis of biosphere reserve Eastern Carpathians with both spectral and morphometric constituents. The Shuttle Radar Topography Mission (SRTM) has provided digital elevation models for approximately 80 % of the earth’s land surface. SRTM data are used to calculate first derivatives (slope) and second derivatives of elevation (such as minimum curvature, maximum curvatures, and cross-sectional curvature) by fitting a bivariate quadratic surface with a window size of 9 by 9. Together with multispectral remote sensing data like Landsat 7 ETM+ with 28.5 m raster elements, these data provide comprehensive information for the analysis of the landscape in the study area. Unsupervised neural network algorithm—self-organizing map—divided all input vectors into inclusive and exhaustive classes on the basis of similarity between attribute vectors. An optimal self-organizing map with 21 classes using 1,000 iterations and a final neighborhood radius of 0.05 provided a low average quantization error of 0.3394 and was used for further analysis. Morphometric analysis, spectral signature analysis, and feature space analysis are used to assign semantic meaning to the classes as landscape elements according to form, cover, and slope, e.g., deciduous forest on ridge (convex landform) with steep slopes. The results revealed the efficiency of self-organizing map to integrate SRTM and Landsat data for landscape classification. This makes it possible to develop an alternative method for fast assessment and comparison of landscapes over large areas. This procedure is reproducible for the same applications with consistent results. 相似文献
126.
Ocean Science Journal - Metal concentrations were measured in predominant coastal fauna of the Caspian Sea including six macro-invertebrates (Mnemiposis leidyi, Balanus improvisus, Pontogammarus... 相似文献
127.
Amir Esna-Ashari Jamshid Hassanzadeh Mohammad-Vali Valizadeh 《Mineralogy and Petrology》2011,101(3-4):195-216
Microgranular enclaves are common in the Jurassic Aligoodarz granitoids of western Iran. Enclaves Enclosed in Granodiorite (EEG) and Enclaves Enclosed in Tonalite (EET) are different but they overlap their hosts on variation diagrams. The EEG is compositionally intermediate between tonalite and granodiorite. Mixing between tonalitic and granodioritic magmas and fractional crystallization are two models examined as the origin of the EEG. Field, textural, mineralogical and chemical observations suggest that chemical equilibration, common in magma mixing, was not attained between the EEG and its host. This, together with other observations does not support magma mixing as a mechanism for forming the EEG. Alternatively, excessive nucleation of biotite ± Fe-Ti-oxides ± amphibole by rapid cooling at borders of a shallow magma chamber and later fragmentation and dispersal by dynamic arc plutonism best explains the EEG. However, channeling of a new magma into the nearly solid tonalitic host explains formation of the EET. 相似文献
128.
Causes and extent of environmental impacts of landslide hazard in the Himalayan region: a case study of Murree, Pakistan 总被引:2,自引:2,他引:0
Pakistan is located at the cross-roads of plate boundaries, experiencing multiple hazards of earthquake, flood, drought, water-logging, salinization and recurrent landslides. This paper examines the causes and environmental impacts of frequently occurring landslide hazards in the Murree area of Pakistan??s Himalayan region. These are wide ranging in nature and in terms of the damage that result. The area under research was divided into eight blocks and randomly data collected. It was observed that landslides mostly occur along the road network and disturbed slopes. Immature geology, a wide variation in climate and degradation of the natural resource-base were found to be some of the causal factors responsible for the landslide hazards. During the past three decades, rapid expansion of urban zones contributed to the changing vulnerability of the area. The analysis revealed that a large majority of the households (75%) in the area have been directly or indirectly affected by landslide hazards. Damages to already scarce agricultural land, infrastructure and other properties are each year a regular and escalating phenomenon. Landslide size, frequency and consequent costs of damage have increased considerably. 相似文献
129.
Amir M. Abdolahzadeh Benoit Lacroix Vachon Alexandre R. Cabral 《Geotechnical and Geological Engineering》2011,29(5):783-802
One important step in the design of inclined covers with capillary barrier effect (CCBE) is the determination of the water
diversion length (DL). Numerical simulations can predict the DL more precisely than steady-state analytical solutions. Nevertheless,
as simplified methods have always been part of engineering design, the application of analytical solutions with conservative
boundary conditions, may allow engineers to make reasonable predictions, particularly during the pre-feasibility stage of
a project. In this study, a CCBE was designed, constructed and instrumented at the Saint-Tite-des-Caps landfill, Quebec, Canada.
This CCBE included a seepage control layer superimposing a sand-gravel capillary barrier. The seepage control layer was made
up of deinking by-products (DBP), an industrial by-product that was previously disposed of as waste. The capillary barrier
was designed using an adaptation of the Ross analytical solution and the scenario considered was that of steady-state flow
during constant seepage flow applied uniformly at the top of the sand-gravel capillary barrier. Although these conditions
appear simplistic, they were deemed reasonable because placement of the seepage control layer on the top of the capillary
barrier led to very low suctions at the interface, thereby allowing uniform downward seepage rates, limited by the saturated
hydraulic conductivity of the DBP. In this paper, a discussion about the behaviour of the cover system based on 4 years of
field data from several instruments is presented. The challenge of using DBP, more precisely the settlement of the DBP layer
and its impact on k
sat
, is also assessed. The DL was reassessed considering the new k
sat
. A discussion on the validity of employing analytical solutions to determine DL is also presented. This paper illustrates
how certain variables affect the design of inclined CCBEs that include a highly compressible material as seepage control layer. 相似文献
130.