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991.
Ali Haydar Kayhan Kasım Armagan Korkmaz Ayhan Irfanoglu 《Soil Dynamics and Earthquake Engineering》2011
In this study, a solution model is proposed to obtain input ground motion datasets compatible with given design spectra based on meta-heuristic harmony search algorithm. The utility of the solution model is demonstrated by generating ground motion datasets matching the Eurocode-8 design spectra for different soil types out of an extensive database of recorded motions. A total of 352 records are selected from the Pacific Earthquake Engineering Center (PEER) Strong Motion Database based on magnitude, distance, and site conditions to form the original ground motion domain. Then, the proposed harmony search based solution algorithm is applied on the pre-selected 352 time-series to obtain the ground motion record sets compatible with design spectra. The results demonstrate that the proposed HS based solution model provides an efficient way to develop input ground motion record sets that are consistent with code-based design spectra. 相似文献
992.
Pb isotopic variability in the modern-Pleistocene Indus River system measured by ion microprobe in detrital K-feldspar grains 总被引:1,自引:0,他引:1
Anwar Alizai Peter D. Clift Sam VanLaningham Ali R. Tabrez The Edinburgh Ion Microprobe Facility 《Geochimica et cosmochimica acta》2011,75(17):4771-4795
The western Himalaya, Karakoram and Tibet are known to be heterogeneous with regard to Pb isotope compositions in K-feldspars, which allows this system to be used as a sediment provenance tool. We used secondary ion mass spectrometry to measure the isotopic character of silt and sand-sized grains from the modern Sutlej and Chenab Rivers, together with Thar Desert sands, in order to constrain their origin. The rivers show a clear Himalayan provenance, contrasting with grains from the Indus Suture Zone, but with overlap to known Karakoram compositions. The desert dunes commonly show 207Pb/204Pb and 206Pb/204Pb values that are much higher than those seen in the rivers, most consistent with erosion from Nanga Parbat. This implies at least some origin from the trunk Indus, probably reworked by summer monsoon winds from the SW, a hypothesis supported by bulk Nd and U-Pb zircon dating. Further data collected from Holocene and Pleistocene sands shows that filled and abandoned channels on the western edge of the Thar Desert were sourced from Himalayan rivers before and at 6-8 ka, but that after that time the proportion of high isotopic ratio grains rose, indicating increased contribution from the Thar Desert dunes prior to ∼4.5 ka when flow ceased entirely. This may be linked to climatic drying, northward expansion of the Thar Desert, or changes in drainage style including regional capture, channel abandonment, or active local Thar tributaries. Our data further show a Himalayan river channel east of the present Indus, close to the delta, in the Nara River valley during the middle Holocene. While this cannot be distinguished from the Indus it is not heavily contaminated by reworking from the desert. The Pb system shows some use as a provenance tool, but is not effective at demonstrating whether these Nara sediments represent a Ghaggar-Hakra stream independent from the Indus. Our study highlights an important role for eolian reworking of floodplain sediments in arid rivers such as the Indus. 相似文献
993.
Roohollah Sadeghi Ali Mohebbi Mehdi Baniasadi 《International Journal of Mineral Processing》2011,98(1-2):55-65
In this study, a computational fluid dynamics (CFD) modeling accompanied by experimental field measurements has been applied to study the behavior of aqueous–organic dispersion on the performance of the launder of the settler of the copper solvent extraction plant at the Sarcheshmeh copper complex, Iran. Fluid flow field has been calculated by solving the continuity and Navier Stokes equations along with the standard k-ε turbulence model. The simulation results have been compared with the field measurements data to check the accuracy of the CFD work. The effects of picket fence on the launder performance and pressure drop over the picket fences in the launder have been investigated. The model predicts that by setting the picket fences, flow pattern becomes uniform, and turbulent eddies disappear. The results also show that by installing two picket fences without dam in the launder, the phase separation is improved and the performance of the launder is optimized. 相似文献
994.
Richard N. Hiscott Ali E. Aksu Roger D. Flood Vladimir Kostylev Doğan Yaşar 《Sedimentology》2013,60(7):1639-1667
Seaward of the Bosphorus Strait, the south‐west Black Sea shelf is dominated by the world's largest channel network maintained by a quasi‐continuous saline (ca 35 → 31 psu) underflow. Calculations indicate that >85% of the initial discharge of ca 104 m3s?1 spills overbank before the shelf edge. This paper documents interaction of the overspill with sea bed topography using multibeam bathymetry, echo‐sounder images of the water column, conductivity–temperature–depth profiles and sediment cores. Overbank spill is widespread, particularly through crevasse channels and on the middle shelf where confinement by channel banks is negligible. Towards the outer shelf, the wind‐driven Rim Current advects mud along the shelf, contributing to levée successions and deposition on stoss sides of elongate transverse ridges. Echo‐sounder profiles reveal metre‐scale eddies over megaflutes, and breaking lee waves and internal hydraulic jumps over ridges. Megaflutes reach 600 m long and 7 m deep, yet form where the underflow, outside the flute, is no thicker than ca 2 to 5 m. Two types of elongate seaward‐facing ridges are recognized. Type 1 ridges, 2 to 5 m high, consist of bivalve‐rich muddy sand in low‐angle (3·5° to 6°) cross‐sets created by the underflow. Type 2 ridges, ca 5 m high, have crests up to 2 km long and a buried wedge‐shaped foundation (the ‘ridge‐core’) comprised of facies similar to Type 1 ridges. These ridge‐cores are blanketed on the landward side by stratified muds, and are capped by obliquely oriented ribs supporting a diverse benthic community. This facies distribution is interpreted to result from stoss‐side and lee‐side velocity and turbulence fluctuations induced by internal hydraulic jumps and breaking lee waves in overspilling portions of the underflow. Experimental results published by W.H. Snyder and co‐workers effectively explain ridge evolution and flow across the ridges, and therefore can be applied with confidence to less easily studied deep‐marine settings swept by turbidity currents. 相似文献
995.
Saudi Arabia has in recent years experienced frequent disasters, including flooding, epidemics, and dust storms, while many parts of the country are subject to regular earthquake and volcanic activity. The paper examines public perception of the risk of disasters in this interesting socio-cultural and regional environment not already covered by existing literature. A wide national survey conducted between March and May 2012 resulted in 1,164 responses across the 13 regions of Saudi Arabia. The study showed that the majority of the participants have faith that God is in control of the world and that disasters may be a punishment from him. However, this does not hinder their desire to be prepared to cope with disasters. It also highlighted that direct experience with such disasters does not directly influence perception. The research findings lead to the emergence of a number of recommendations regarding raising awareness of hazards and the risk of disasters, including education, training, encouraging voluntary work, and improving public access to vital information resources. A requirement for research into resilience also emerges, to prepare communities to cope with disasters; this is the focus of the authors’ future research. 相似文献
996.
Ali Soleimanbeigi 《Geotechnical and Geological Engineering》2013,31(5):1511-1524
Undrained shear strength (su) of foundation soil of Marquette interchange near Milwaukee, Wisconsin was evaluated from the results of a number of pressuremeter tests conducted on normally consolidated (NC) organic silts and overconsolidated (OC) silty clay. The su-values were interpreted from traditional closed-form methods. The pressuremeter geometry and test sequence as well as response of the soil profiles were also simulated using axisymmetric finite element (FE) method with Cam-Clay soil model. The Cam-Clay model parameters were estimated from laboratory tests on undisturbed soil samples. Results show that the su estimated from the rate of cavity pressure change with volumetric strain (referred to as direct traditional method) is almost twice the su estimated from an indirect traditional method that estimates su from shear modulus, in situ horizontal stress, and ultimate cavity pressure obtained from the cavity pressure curves. The su-values predicted from the FE models are lower than those estimated from the traditional methods and shows that the assumption of infinite pressuremeter length in traditional methods results in overprediction of undrained shear strength by a factor of 1.5 for NC clay and 2.2 for OC clay. The results of finite element analysis considering Cam-Clay soil model and finite length for pressuremeters suggest the undrained shear strength of 63 ± 7 kPa for NC organic silt and 259 ± 68 kPa for OC silty clay. 相似文献
997.
998.
In the vicinity of Konya (Turkey),mafic,micro-porphyritic sub-volcanic rocks intrude into the Mesozoic units,which represents the only example of such a rock type in the region.40Ar/39Ar dating of two whole rock samples from the sub-volcanics gave ages of 13.72±0.13 and 12.40±0.11 Ma,suggesting temporal association to the Late Miocene-Pliocene high-K calc-alkaline volcanism in the region.The mineral chemistry and geochemical data permit us to classify the rocks as "minette" lamprophyres.They include diopside and phlogopite phenocrysts in a microcrystalline groundmass composed of sanidine,phlogopite,diopside and titano-magnetite.Segregation and ocelli-like globular structures occur commonly in the samples.In terms of major elements,the lamprophyres are calcalkaline,and potassic to ultrapotassic rocks.All the lamprophyres display strong enrichments in LILE (Rb,Ba,K,Sr),radiogenic elements (Th,U) and LREE (La,Ce) and prominent negative Nb,Ta,and Ti anomalies on primordial mantle-normalized trace element diagrams.Geochemical data suggest that the lamprophyres and high-K calc-alkaline rocks in the region derived from a subduction-modified lithospheric mantle source affected by different metasomatic events.Lamprophyric magmatism sourced phlogopite-bearing veins generated by sediment-related metasomatism via subduction,but high-K calc-alkaline magmas are possibly derived from a mantle source affected by fluid-rich metasomatism. 相似文献
999.
AbstractA large sinistral intracontinental transcurrent structure, the Central Anatolian Fault Zone (CAFZ), is located between Erzincan in the northeast and offshore of Anamur county in the southwest of Turkey. Northeastern and southwestern segments of the fault zone are linked to each other by an intervening and approximately N-S-trending transtensional structure, the Erciyes pull-apart hasin (EPB). The Krzihrmak-Erkilet and Dökmeta? segments of the CAFZ bend southwards at about 45°-50° near Kayseri and result in a releasing double bend, which has nucleated both the EPB and its main feature, the Erciyes stratovolcano complex (ESVC) since Middle Pliocene time. The EPB is a ~35-km-wide, 120-km-long, 1.2-km-deep, lazy S-shaped and actively-growing depression with the ESVC forming a high-standing central barrier between the northern and southern parts of the basin. Hence, the EPB appears as two separate basins, namely the ‘Sultansazh?i and Kayseri-Sarimsakli depressions’. However, this is not correct, because development of the EPB and ESVC has been coeval with the volcanic activity producing the ESVC continuing into prehistoric times. Development of the EPB is continuing as indicated by faulted, uplifted and terraced Pleistocene-Early Holocene palaeolake beach deposits, and historical to recent earthquakes. Accumulative throws on the eastern and western margin-bounding faults of the EPB are 1225 m and 720 m respectively and show that basin development has been asymmetrical. © 2001 Éditions scientifiques et médicales Elsevier SAS 相似文献
1000.
Hydrogeochemistry and arsenic contamination of groundwater in the Rayen area, southeastern Iran 总被引:1,自引:1,他引:0
High As contents in groundwater were found in Rayen area and chosen for a detailed hydrogeochemical study. A total of 121 groundwater samples were collected from existing tube wells in the study areas in January 2012 and analyzed. Hydrogeochemical data of samples suggested that the groundwater is mostly Na–Cl type; also nearly 25.62 % of samples have arsenic concentrations above WHO permissible value (10 μg/l) for drinking waters with maximum concentration of aqueous arsenic up to 25,000 μg/l. The reducing conditions prevailing in the area and high arsenic concentration correlated with high bicarbonate and pH. Results show that arsenic is released into groundwater by two major phenomena: (1) through reduction of arsenic-bearing iron oxides/oxyhydroxides and Fe may be precipitated as iron sulfide when anoxic conditions prevail in the aquifer sediments and (2) transferring of As into the water system during water–acidic volcanic rock interactions. 相似文献