排序方式： 共有13条查询结果，搜索用时 78 毫秒
1.
Mahmoud Behnia Ahmad Rahmani Shahraki Zabihallah Moradian 《Geotechnical and Geological Engineering》2018,36(4):1975-1989
Many surface and underground structures are constructed in heterogeneous rock formations. These formations have a combination of weak and strong rock layers. Due to the alternation of the weak and strong layers, selecting the equivalent and appropriate geomechanical parameters for these formations is challenging. One of these problems is choosing the equivalent strength (i.e., uniaxial compressive strength) of intact rock for a group of rocks. Based on the volume of weak and strong parts and their strength, the equivalent strength of heterogeneous rocks changes. Marinos and Hoek (Bull Eng Geol Environ 60(2):85–92, 2001) presented the “weighted average method” for defining the uniaxial compressive strength (UCS) of heterogeneous rock masses based on the volume of weak and strong parts. Laubscher (1977) used the volume ratio of the strength of a weak part to a strong part (UCS weak/UCS strong) to determine the equivalent strength. In this study, the two methods are compared and their validity is evaluated by experimental data and numerical analyses. The geomechanical parameters of two heterogeneous formations (Aghajari and Lahbari) in the west of Iran were estimated using these methods. The results of the present study obtained through numerical analyses using particle flow code are compared with those of previous studies and discussed. Laboratory and numerical results show UCS decrease and approach to weak strength with an increasing in volume of weak part. When strength ratio of strong to weak rock increase, equivalent strength decrease more severely. The findings show that Laubscher’s method gives more appropriate results than the weighted average method. 相似文献
2.
Isabelle McMartin Pierre-Marc Godbout Janet E. Campbell Tommy Tremblay Pouran Behnia 《Boreas: An International Journal of Quaternary Research》2021,50(1):51-75
A new digital map of glacial geomorphic features and interpreted glacial landsystems was produced for an area covering ~415 000 km2 in the Keewatin Sector of the Laurentide Ice Sheet (LIS) in Nunavut. The map integrates information from previous surficial geology maps and >14 000 field stations, and is significantly improved by the detailed inventory of ~152 000 glacigenic features using high-resolution ArcticDEM data and Landsat 8 imagery. From this, we identify and map coherent patterns of landform development (landsystems) between the Manitoba border and the Arctic coast, many of which are entirely new and others that are significantly modified or updated. In particular, we recognize six separate ice streams, including one probable remnant ice stream, and we delineate numerous palimpsest streamlined landscapes with associated ice-flow trends and relative ages. A continuum of relict terrains with varying basal ice thermal conditions is mapped for the first time in the ice divide migration zone between Baker Lake and Wager Bay. In addition, deglacial cold-based retreat terrains and preserved warm-based landscapes unaffected by younger glacial events have been identified. These new georeferenced, multi-scale data sets and interpreted glacial landsystems provide a comprehensive framework to strengthen reconstructions of the glacial history and dynamics of one of the largest ice domes of the LIS, identify distinct glacial sediment transport paths for applications to mineral exploration, and test numerical modelling of the LIS in support of climate change studies and long-term evolution of modern ice sheets. 相似文献
3.
Pouran Behnia 《地球空间信息科学学报》2013,16(2):98-103
Four data fusion methods, principle component transform (PCT), brovey transform (BT), smoothing filter-based intensity modulation (SFIM), and hue, saturation, intensity (HSI), are used to merge Landsat—7 ETM+ multispectral bands with ETM+ panchromatic band. Each of them improves the spatial resolution effectively but distorts the original spectral signatures to some extent. SFIM model can produce optimal fusion data with respect to preservation of spectral integrity. However, it results the most blurred and noisy image if the coregistration between the multispectral and pan images is not accurate enough. The spectral integrity for all methods is preserved better if the original multispectral images are within the spectral range of ETM+ pan image. 相似文献
4.
Comparison Between Four Methods for Data Fusion of ETM＋ Multispectral and Pan Images 总被引：2，自引：0，他引：2
PouranBehnia 《地球空间信息科学学报》2005,8(2):98-103
Four data fusion methods, principle component transform (PCT), brovey transform (BT), smoothing filter-based intensity modulation(SFIM), and hue, saturation, intensity (HSI), are used to merge Landsat--7 ETMq- multispectral bands with ETM panchromatic band. Each of them improves the spatial resolution effectively but distorts the original spectral signatures to some extent. SFIM model can produce optimal fusion data with respect to preservation of spectral integrity. However, it results the most blurred and noisy image if the coregistration between the multispectral and pan images is not accurate enough. The spectral integrity for all methods is preserved better if the original multispectral images are within the spectral range of ETM pan image. 相似文献
5.
Natural Resources Research - The uniaxial compressive strength and static Young’s modulus are among the key design parameters typically used in geotechnical engineering projects. In this... 相似文献
6.
Regional analysis of wind climatic erosivity factor: a case study in fars province, southwest Iran 总被引：1，自引：0，他引：1
Wind erosion climatic erosivity is a measure of the climatic tendency to produce conditions conducive to wind erosion. This research develops a method to determine the regional climate’s tendency to cause wind erosion on the basis of a physically based climatic factor (CE) and linear moment analysis (L-moments) in Fars province, southwest Iran. CE is calculable from wind speed quantiles and other available meteorological data. The wind quantiles can be estimated by a frequency analysis of the available wind data. Wind speed data are often either not available or are of short record length, and thus, CE estimates from such data have large standard errors. In such a situation, data from several sites can be used to estimate wind speed quantiles at each site based on a regional frequency analysis. Monthly averages of maximum daily wind speed of 19 meteorological stations in Fars province were used for regional analysis. Based on L-moment analysis, two homogeneous regions were determined. Regional wind speed quantiles were calculated, and the results were used to calculate CE values for two 6-month wet and dry periods for each homogeneous region. Furthermore, CE values were estimated for each station in the study area using a Weibull distribution, and the results were compared with the regional-based CE values. It showed that CE values estimated using the regional-based approach have smaller sampling variance compared to those obtained from the Weibull method. The proposed method can be used to evaluate the regional risk of wind erosion in arid and semi-arid environments. 相似文献
7.
Controlled laboratory experiments were performed in a water tank to study energy transfer during cooling and radiant reheating of water from above. Accurate instantaneous temperature measurements were obtained using a Mach-Zehnder interferometer which did not disturb the temperature, radiation, and flow fields. The buoyancy induced flow field was visualized by employing an electro-chemical dye production technique. Cooling of initially uniform layer of water and stratification-cooling-restratification were studied.The experimental observation during cooling of an initially uniform temperature column of water indicated intermittent free convection near the surface. The phenomenon was characterized by randomly descending cooler plumes penetrating 10 to 25 cm into the warmer underlying region. The cooling rate had a decisive influence on the frequency and intensity of the descending parcels of water. For lower cooling rates the colder water usually descended in a form of sheets.Observations during cooling of initially stratified water showed that buoyancy driven convection occurred near the surface. The motion had an initial regular roll pattern, but as the cooling continued the roll pattern in the convective (mixed) layer deteriorated into motion similar to that observed during cooling of an initially uniform temperature layer of water. When the water was restratified by radiant heating, the circulation in the convective layer was suppressed, and the temperature profiles obtained were similar to those observed in a fluid during free convection between two solid parallel walls. 相似文献
8.
Nicholas Williamson Atsuki Komiya Shigenao Maruyama Masud Behnia Steve W. Armfield 《Journal of Oceanography》2009,65(3):349-359
The transport of nutrient-rich, deep sea water from an artificial upwelling pipe has been simulated. A numerical model has
been built within a commercial Computational Fluid Dynamics (CFD) package. The model considers the flow of the deep sea water
after it is ejected from the pipe outlet in a negatively buoyant plume (densimetric Froude number = −2.6), within a stably
stratified ocean environment subject to strong ocean current cross flow. Two cross-flow profiles were tested with momentum
flux ratios equal to 0.92 and 3.7. The standard k-ε turbulence model has been employed and a range of turbulent Schmidt and Prandtl numbers tested. In all cases the results
show that the rapid diffusion of heat and salinity at the pipe outlet causes the plume to attain neutral buoyancy very rapidly,
preventing strong fountain-like behavior. At the higher momentum flux ratio fountain-like behavior is more pronounced close
to the pipe outlet. The strong cross-current makes horizontal advection the dominant transport process downstream. The nutrient
plume trajectory remains largely within one relatively thin stratified layer, making any ocean cross-flow profile less important.
Very little unsteady behavior was observed. The results show that the nutrient is reduced to less than 2% of its inlet concentration
10 meters downstream of the inlet and this result is largely independent of turbulent Prandtl or Schmidt number. Initial results
would suggest that if such an artificial upwelling were to be viable for an ocean farming project, a large number of upwelling
pipes would be necessary. Further work will have to determine the minimum nutrient concentration required to sustain a viable
phytoplankton population and the required spacing between upwelling pipes. 相似文献
9.
Pouran Behnia 《Natural Resources Research》2007,16(2):157-158
The metallogeny of Central Iran is characterized mainly by the presence of several iron, apatite, and uranium deposits of
Proterozoic age. Radial Basis Function Link Networks (RBFLN) were used as a data-driven method for GIS-based predictive mapping
of Proterozoic mineralization in this area. To generate the input data for RBFLN, the evidential maps comprising stratigraphic,
structural, geophysical, and geochemical data were used. Fifty-eight deposits and 58 ‘nondeposits’ were used to train the
network. The operations for the application of neural networks employed in this study involve both multiclass and binary representation
of evidential maps. Running RBFLN on different input data showed that an increase in the number of evidential maps and classes
leads to a larger classification sum of squared error (SSE). As a whole, an increase in the number of iterations resulted
in the improvement of training SSE. The results of applying RBFLN showed that a successful classification depends on the existence
of spatially well distributed deposits and nondeposits throughout the study area.
An erratum to this article can be found at 相似文献
10.
PouranBehnia LorenceGCollins BahrainASamani 《中国地质大学学报(英文版)》2003,14(1):34-41
The Qooshchi area lies to northwest of Orumieh Lake in western Azerbaijan, NW Iran. A basement metamorphic complex, consisting of Precambrian schists and gneisses, has been intruded by gabbres and diorites. Granitolds are grouped into five suites according to their mineralogy, texture and exposed features. The main body, pink Qooshchi granite, and apophyse-like, myrmekite-bearing granit-oids are discussed in this paper. On the basis of field observations and microscopic studies, an intensive metasonmtism has overprinted the country rocks, especially gabbros, transforming them into a more felsic composition. A prior event of intensive deformation and cataclasis preceded the metasonmtism, al-lowing the introduction of hydrothermal fluids. K-metasonmtism converted plagiuclase into K-feldspar (microdme), myrmekite, and sodic plagioclase as Si-metasomatism replaced the ferromagnesian silicates by quartz. Apophyse-like bodies within gabbros, called leucometasomatites, are formed during this process. 相似文献