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31.
Abstract The northern part of the Aravalli mountain belt of northwestern Indian shield is broadly composed of three Proterozoic volcano-sedimentary domains, i.e. the Bayana, the Alwar and the Khetri basins, comprising collectively the north Delhi fold belt. Major, trace and rare earth element concentrations of mafic volcanic rocks of the three basins exhibit considerable diversity. Bayana and Alwar volcanics are typical tholeiites showing close similarity with low Ti–continental flood basalts (CFB) with the difference that the former shows enriched and the latter flat incompatible trace element and rare earth element (REE) patterns. However, the Khetri volcanics exhibit a transitional composition between tholeiite and calc-alkaline basalts. It appears that the melts of Bayana and Alwar tholeiites were generated by partial melting of a common source within the spinel stability field possibly in the presence of mantle plume. During ascent to the surface the Bayana tholeiites suffered crustal contamination but the Alwar tholeiites erupted unaffected. Geochemically, the Khetri volcanics are arc-like basalts which were generated in a segment of mantle overlying a Proterozoic subduction zone. It is suggested that at about 1800 Ma the continental lithosphere in northeastern Rajasthan stretched, attenuated and fractured in response to a rising plume. The produced rifts have undergone variable degrees of crustal extension. The extension and attenuation of the crust facilitated shallowing of the asthenosphere which suffered variable degree of melting to produce tholeiitic melts – different batches of which underwent different degrees of lithospheric contamination depending upon the thickness of the crust in different rifted basins. The occurrence of subduction-related basaltic rocks of Khetri Belt suggests that a basin on the western margin of the craton developed into a mature oceanic basin. 相似文献
32.
ABSTRACTUser-Generated Content (UGC) provides a potential data source which can help us to better describe and understand how places are conceptualized, and in turn better represent the places in Geographic Information Science (GIScience). In this article, we aim at aggregating the shared meanings associated with places and linking these to a conceptual model of place. Our focus is on the metadata of Flickr images, in the form of locations and tags. We use topic modeling to identify regions associated with shared meanings. We choose a grid approach and generate topics associated with one or more cells using Latent Dirichlet Allocation. We analyze the sensitivity of our results to both grid resolution and the chosen number of topics using a range of measures including corpus distance and the coherence value. Using a resolution of 500 m and with 40 topics, we are able to generate meaningful topics which characterize places in London based on 954 unique tags associated with around 300,000 images and more than 7000 individuals. 相似文献
33.
Syed Wajid Ali Shah Mujaddad ur Rehman Samina Anwar Azam Hayat Ghulam Shabir Razia Tahseen Moazur Rahman Ejazul Islam Samina Iqbal Muhammad Afzal 《洁净——土壤、空气、水》2023,51(2):2100435
The presence of trace antibiotics in domestic and industrial effluents poses a risk of toxicity to fauna and flora. The application of floating treatment wetlands (FTWs) is a low-cost and sustainable approach to remediate wastewater. In this study, the performance of different macrophytes vegetated in FTWs for the remediation of ciprofloxacin (CIP)-contaminated water is investigated. Six macrophytes, Brachia mutica, Typha domingensis, Phragmites australis, Canna indica, Cyperus laevigatus, and Leptochloa fusca, are vegetated in FTWs for the removal of CIP (50 mg L−1) from water. The FTWs show the potential to remove 30–43.58 mg L−1 CIP from water in 28 days. They also reduce the chemical oxygen demand (118–138 mg L−1) and biochemical oxygen demand (35–45 mg L−1) of water. Among the macrophytes, C. indica removes maximum (43.58 mg L−1) and T. domingensis minimum (30 mg L−1) CIP. Canna indica and T. domingensis exhibit the maximum and minimum increase (30% and 12% of dry biomass) in growth, respectively. This study reveals that the FTWs vegetated with different plant species exhibit varying performances in removing CIP from water. This investigation is a step forward toward sustainable bioremediation of water contaminated with antibiotics. 相似文献
34.
A start‐up study for biohydrogen production from palm oil mill effluent (POME) is carried out in a pilot‐scale up‐flow anaerobic sludge blanket fixed‐film reactor (UASFF). A substrate with a chemical oxygen demand (COD) of 30 g L?1 is used, starting with molasses solution for 30 days and followed by a 10% v/v increment of POME/molasses ratio. At 100% POME, a hydrogen content of 80%, hydrogen production rate of 36 L H2 per day, and maximum COD removal of 48.7% are achieved. Bio‐kinetic coefficients of Monod, first‐order, Grau second‐order, and Stover‐Kincannon kinetic models are calculated to describe the performance of the system. The steady‐state data with 100% POME shows that Monod and Stover‐Kincannon models with bio‐kinetic coefficients of half‐velocity constant (Ks) of 6000 mg COD L?1, microbial decay rate (Kd) of 0.0015 per day, growth yield constant (Y) of 0.786 mg volatile suspended solids (VSS)/mg COD, specific biomass growth rate (μmax) of 0.568 per day, and substrate consumption rate of (Umax) 3.98 g/L day could be considered as superior models with correlation coefficients (R2) of 0.918 and 0.989, respectively, compared to first‐order and Grau's second‐order models with coefficients of K1 1.08 per day, R2 0.739, and K2s 1.69 per day, a = 7.0 per day, b = 0.847. 相似文献
35.
Expansive soils exhibit large volume changes when their water content changes. Alternate heave and settlement due to seasonal
climatic variations result in distress and damage in civil infrastructure systems. This research focuses on the understanding
of swelling and shrinkage phenomenon in the surface layer of expansive soils. Undisturbed field samples were used to capture
the effect of in situ conditions (geologically induced fissuring and environmentally caused saturation) on volume change properties of Regina clay.
Based on laboratory investigations, the swelling potential and swelling pressure of the native clay at S = 82% were found to be 1.5% and 3.5 kPa, respectively. The swell-shrink path during progressive soil drying followed an S-shaped curve comprising of an initial low structural shrinkage followed by a sharp decline during normal shrinkage and then
by a low decrease during residual shrinkage. The soil microstructure correlated well with the observed volume change behaviour
as well as with the consistency limits. The presence of fissures in field samples at various degrees of saturation confirmed
that the investigated deposit is at an equilibrium condition with respect to the swell-shrink phenomenon. The swelling properties
at any initial saturation state were estimated using the free swelling test and the swell-shrink test data in conjunction.
The swelling potential increased 12 times (from 2 to 24%) and the swelling pressure increased by two orders of magnitude (from
27 to 2500 kPa) with a change in the degree of saturation from 80% (at the plastic limit) to 60% (at the shrinkage limit). 相似文献
36.
K M Azam Chowdhury Wensheng Jiang Changwei Bian Guimei Liu Md Kawser Ahmed Shaila Akhter 《海洋学报(英文版)》2022,41(9):19-37
Variations in incoming shortwave radiation influence the net surface heat flux, contributing to the formation of a temperature inversion. The effects of shortwave radiation on the temperature inversions in the Bay of Bengal and eastern equatorial Indian Ocean have never been investigated. Thus, a high-resolution (horizontal resolution of 0.07°×0.07° with 50 vertical layers) Regional Ocean Modeling System (ROMS) model is utilized to quantify the contributions of shortwave radiation to the temperature inversions in the study domain. Analyses of the mixed layer heat and salt budgets are performed, and different model simulations are compared. The model results suggest that a 30% change in shortwave radiation can change approximately 3% of the temperature inversion area in the Bay of Bengal. Low shortwave radiation reduces the net surface heat flux and cools the mixed layer substantially; it also reduces the evaporation rate, causing less evaporative water vapor losses from the ocean than the typical situation, and ultimately enhances haline stratification. Thus, the rudimentary outcome of this research is that a decrease in shortwave radiation produces more temperature inversion in the study region, which is primarily driven by the net surface cooling and supported by the intensive haline stratification. Moreover, low shortwave radiation eventually intensifies the temperature inversion layer by thickening the barrier layer. This study could be an important reference for predicting how the Indian Ocean climate will respond to future changes in shortwave radiation. 相似文献
37.
Ameer A. Jebur William Atherton Rafid M. Al Khaddar Ed Loffill 《Geotechnical and Geological Engineering》2018,36(5):2893-2906
This investigation aimed to examine the load carrying capacity of model piles embedded in sandy soil and to develop a predictive model to simulate pile settlement using a new artificial neural network (ANN) approach. A series of experimental pile load tests were carried out on model concrete piles, comprised of three piles with slenderness ratios of 12, 17 and 25. This was to provide an initial dataset to establish the ANN model, in attempt at making current, in situ pile-load test methods unnecessary. Evolutionary Levenberg–Marquardt (LM) MATLAB algorithms, enhanced by T-tests and F-tests, were developed and applied in this process. The model piles were embedded in a calibration chamber in three densities of sand; loose, medium and dense. According to the statistical analysis and the relative importance study, pile lengths, applied load, pile flexural rigidity, pile aspects ratio, and sand-pile friction angle were found to play a key role in pile settlement at different contribution levels, following the order: P?>?δ?>?lc/d?>?lc?>?EA. The results revealed that the optimum model of the LM training algorithm can be used to characterize pile settlement with good degree of accuracy. There was also close agreement between the experimental and predicted data with a root mean square error, (RMSE) and correlation coefficient (R) of 0.0025192 and 0.988, respectively. 相似文献
38.
A. S.?Ameer M. L.?SharmaEmail author H. R.?Wason S. A.?Alsinawi 《Pure and Applied Geophysics》2005,162(5):951-966
Probabilistic seismic hazard analysis (PSHA) has been carried out for Iraq. The earthquake catalogue used in the present study covers an area between latitude 29°–38.5° N and longitude 39°–50° E containing more than a thousand events for the period 1905–2000. The entire Iraq region has been divided into thirteen seismogenic sources based on their seismic characteristics, geological setting and tectonic framework. The completeness of the seismicity catalogue has been checked using the method proposed by Stepp (1972). The analysis of completeness shows that the earthquake catalogue is not complete below Ms=4.8 for all of Iraq and seismic source zones S1, S4, S5, and S8, while it varies for the other seismic zones. A statistical treatment of completeness of the data file was carried out in each of the magnitude classes. The Frequency Magnitude Distributions (FMD) for the study area including all seismic source zones were established and the minimum magnitude of complete reporting (Mc) were then estimated. For the entire Iraq the Mc was estimated to be about Ms=4.0 while S11 shows the lowest Mc to be about Ms=3.5 and the highest Mc of about Ms=4.2 was observed for S4. The earthquake activity parameters (activity rate , b value, maximum regional magnitude mmax) as well as the mean return period (R) with a certain lower magnitude mmin m along with their probability of occurrence have been determined for all thirteen seismic source zones of Iraq. The maximum regional magnitude mmax was estimated as 7.87 ± 0.86 for entire Iraq. The return period for magnitude 6.0 is largest for source zone S3 which is estimated to be 705 years while the smallest value is estimated as 9.9 years for all of Iraq.The large variation of the b parameter and the hazard level from zone to zone reflects crustal heterogeneity and the high seismotectonic complexity. The seismic hazard near the source boundaries is directly and strongly affected by the change in the delineation of these boundaries. The forces, through which the geological structure along the plate boundary in Eastern and Northeastern Iraq are evolved, are still active causing stress-strain accumulation, deformation and in turn producing higher probabilities of earthquake activity. Thus, relatively large destructive earthquakes are expected in this region. The study is intended to serve as a reference for more advanced approaches and to pave the path for the probabilistic assessment of seismic hazard in this region. 相似文献
39.
1 Introduction Theuseofnaturalresources ,includingthosebeingofseeminglymarginalvalue ,isanimportanthumanactivitydesignedtoincreasefoodproductionandin come .Inagriculture ,soilsmaybetoosalinetosup portprofitablecrophusbandry ,yetsuchsoilmaybeusedalternat… 相似文献
40.
Shahid Azam 《Geotechnical and Geological Engineering》2007,25(3):369-381
Soils containing expansive clays undergo swelling that can be both detrimental and beneficial in various applications. In
the Arabian Gulf coastal region, natural heterogeneous soils containing clay and sand (tills, shales, and clayey sands) support
most of the civil infrastructure systems. Likewise, mixes of clay and sand are used for local earthwork construction such
as roads and landfills. A clear understanding of the swelling behaviour of such soils is pivotal at the outset of all construction
projects. The main objective of this paper was to understand the evolution of swelling with increasing clay content in local
soils. A theoretical framework for clay–sand soils was developed using phase relationships. Laboratory investigations comprised
of mineralogical composition and geotechnical index properties of the clay and sand and consistency limits, swelling potential,
and morphology of clay–sand mixes. Results indicated that soil consistency of mixes of a local expansive clay and an engineered
sand depends on the weighted average of the constituents. Mixes with 10% clay through 40% clay capture the transition from
a sand-like behaviour to a clay-like behaviour. Influenced by the initial conditions and soil matrix, the swelling potential
of the investigated mixes correlated well with soil plasticity (SP(%) = 0.16 (I
p)1.188). The parameters sand void ratio and clay–water ratio were found to better explain the behaviour of blended clay–sand soils. 相似文献