Fabrication of Nanoparticle-Doped Polyvinyl Alcohol-Cellulose Acetate Membrane and Characterization of the Surface Enhancement     

Sathish Raam Ravichandran  Chitra Devi Venkatachalam  Mothil Sengottian  Sarath Sekar  Bhavya Shri Subramaniam Ramasamy  Sakthivel Elangovan  Siddharth Thorali Sivakumar  Shanmuga Sundaram Subramanian 《洁净——土壤、空气、水》2023,51(3):2100305

In the present study, nanocomposite polymeric membranes are fabricated using polyvinyl alcohol (PVA), cellulose acetate (CA) as polymers, and dimethyl sulfoxide (DMSO) as the solvent. To enhance the performance of the membrane, nanoparticles like TiO₂, CaO, CdO, and ZrO are added to the polymeric solution and the doped polymeric solution is cast on a glass plate. Nine combinations of membranes are fabricated with two different concentrations (0.1% and 0.2%) of nanoparticles. The basic properties of the membranes such as density, porosity, viscosity, permeability, pure water flux, and water content are studied for the samples. Membrane pore structure and surface properties are identified and it is found that doping nanoparticles on the surface of membranes improve mechanical strength, stability, pore size, etc., allowing the membranes to perform better in extreme industrial-level effluent treatment applications. High-resolution scanning electron microscopy (SEM) shows the homogeneous dispersion of ZrO, TiO₂, CaO, and CdO nanoparticles on the surface of the PVA-CA membrane. The doping of nanoparticles on the PVA-CA membrane results in improved mechanical strength and good chemical oxidation stability. In comparison, the PCD-TiO₂ sample shows high thermal stability and oxidation stability at high temperatures until 200°C, which has a high potential for treating industrial effluents.  相似文献   

Deterministic simulation of highly intermittent hydrologic time series     

Mahesh?L.?Maskey  Carlos?E.?PuenteEmail author  Bellie?Sivakumar 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(10):2719-2732

Application of a deterministic geometric approach for the simulation of highly intermittent hydrologic data is presented. Specifically, adaptations of the fractal-multifractal (FM) method and a Cantorian extension are advanced in order to simulate rainfall records measured at the daily scale and encompassing a water year. It is shown, using as case studies 2 years of rainfall sets gathered in Laikakota, Bolivia and Tinkham, Washington, USA, that the FM approach, relying on only at most 8 parameters, is capable of closely preserving either the whole record’s histogram (therefore including moments), the whole data’s Rényi entropy function and/or the maximum number of consecutive zero values present in the sets, resulting in suitable rainfall simulations, whose overall features and textures are similar to those of the observed sets. The study hence establishes the possibility of simulating highly intermittent sets in time in a deterministic and holistic way as a novel parsimonious methodology to supplement available stochastic frameworks.  相似文献   

Coherent modes in multi‐scale variability of precipitation over the headwater catchments in the Pearl River basin,South China          下载免费PDF全文

Jun Niu  Ji Chen  Keyi Wang  Bellie Sivakumar 《水文研究》2017,31(4):948-955

This paper studies the coherent modes of multi‐scale variability of precipitation over the headwater catchments in the Pearl River basin in South China. Long‐term (1952–2000) daily precipitation data spatially averaged for 16 catchments in the basin are studied. Wavelet transform analysis is performed to capture the fluctuation embedded in the time series at different temporal timescales ranging from 6 days to 8.4 years. The catchment clusters of the coherent modes are delineated using the principal component analysis on the wavelet spectra of precipitation. The results suggest that as much as 98% of the precipitation variability is explained by only two coherent modes: high small‐scale mode and high seasonal mode. The results also indicate that a large majority of the catchments (i.e., 15 out of 16) exhibit consistent mode feature on multi‐scale variability throughout three sub‐periods studied (1952–1968, 1969–1984, and 1985–2000). The underlying effects of the coherent modes on the regional flood and drought tendency are also discussed.  相似文献   

Effect of soil variability on the bearing capacity of clay and in slope stability problems     

Amit Srivastava  G.L. Sivakumar Babu   《Engineering Geology》2009,108(1-2):142-152

Site-specific geotechnical data are always random and variable in space. In the present study, a procedure for quantifying the variability in geotechnical characterization and design parameters is discussed using the site-specific cone tip resistance data (q_c) obtained from static cone penetration test (SCPT). The parameters for the spatial variability modeling of geotechnical parameters i.e. (i) existing trend function in the in situ q_c data; (ii) second moment statistics i.e. analysis of mean, variance, and auto-correlation structure of the soil strength and stiffness parameters; and (iii) inputs from the spatial correlation analysis, are utilized in the numerical modeling procedures using the finite difference numerical code FLAC 5.0. The influence of consideration of spatially variable soil parameters on the reliability-based geotechnical deign is studied for the two cases i.e. (a) bearing capacity analysis of a shallow foundation resting on a clayey soil, and (b) analysis of stability and deformation pattern of a cohesive-frictional soil slope. The study highlights the procedure for conducting a site-specific study using field test data such as SCPT in geotechnical analysis and demonstrates that a few additional computations involving soil variability provide a better insight into the role of variability in designs.  相似文献   

Intra-Seasonal Oscillations Associated with Indian Ocean Warm Pool and Summer Monsoon Rainfall and Their Inter-Annual Variability     

P. M. Muraleedharan  P. G. Nisha  P. V. Sathe  K. U. Sivakumar 《Journal of the Indian Society of Remote Sensing》2012,40(1):75-83

Sea surface temperature (SST) and wind speed (WS) derived from Multichannel Scanning Microwave Radiometer (MSMR), onboard IRS-P4 (Oceansat-1) satellite were used to generate spatially averaged (80° to 100° E & 0° to 10° S) daily data during June to September from 1999 to 2001 along with collocated outgoing long wave radiation (OLR) data from NCEP/NCAR reanalysis product. Daily rainfall data over the peninsular India during the above period was taken from the weekly weather report published by the Indian Meteorological Department. The data were then subjected to power spectral analysis. Dominant 30 to 60 days oscillations were observed over both ocean and land during all the 3 years investigated. It is quite interesting to note that the intra-seasonal oscillation with 60 days periodicity dominates in both ocean and land during 1999 and then transforms to 30 and 40 days periodicities in 2000 and 2001 respectively with a phase lag of about 25 to 30 days. It was also observed that the time-latitude section of zonally averaged OLR and TMI derived cloud liquid water data clearly depict the propagation of convection and cloud from the equator to the north at the rate of 0.75° to 1° latitude per day which corroborates well with the rate of propagation derived from the phase lag obtained between the processes occurring at the equatorial Indian Ocean and rainfall recorded at the designated land segments. The results are in good agreement with the observations made by earlier investigators.  相似文献   

DEM Generation for Lunar Surface using Chandrayaan-1 TMC Triplet Data   总被引：1，自引：0，他引：1  

V. Sivakumar  Binay Kumar  Sandeep Kumar Srivastava  B. Gopala Krishna  Pradeep Kumar Srivastava  A. S. Kiran Kumar 《Journal of the Indian Society of Remote Sensing》2012,40(4):551-564

Digital Elevation Model (DEM) is an important prerequisite for understanding the lunar surface. However, making accurate DEM is a very challenging task due to (a) lack of support of projection parameters in COTS packages (eg. PCI Geomatica), which are to be used in generation of Lunar DEM and (b) unavailability of Ground Control Points (GCPs). In the present study, DEM generation of lunar surface was attempted without GCPs using Rational Function (RF) model from Chandrayaan-1 TMC triplet images. In the study, a good correlation (of almost same order) is observed between Nadir-Fore (NF), Nadir - Aft (NA), Fore - Aft (FA) and Fore - Nadir - Aft (FNA) image pairs. The results suggest that DEM for lunar surface can be created without GCPs using RF model.  相似文献   

Reliability Based Earthquake Resistant Design for Internal Stability of Reinforced Soil Structures     

B. Munwar Basha  G. L. Sivakumar Babu 《Geotechnical and Geological Engineering》2011,29(5):803-820

This paper presents a method to evaluate reliability for internal stability of reinforced soil structures using reliability based design optimization. Using limit equilibrium method and assuming the failure surface to be logarithmic spiral, analysis is conducted to maintain internal stability against both tensile and pullout failure of the reinforcements. Properties of backfill soil and strength of the geosynthetic reinforcement are considered as random variables. For the seismic conditions, reliability indices of all the geosynthetic layers in relation to tension and pullout failure modes are determined for different magnitudes of seismic accelerations both in the horizontal and vertical directions, surcharge load and design strength of the reinforcement. The efforts have been made to obtain the number of layers, pullout length and total length of the reinforcement at each level for the desired target reliability index values against tension and pullout modes of failure. The influence of horizontal and vertical earthquake acceleration, surcharge load, design strength of the reinforcement, coefficient of variation of soil friction angle and design strength of the reinforcement on number of layers, pullout length and total length of the reinforcement needed for the stability at each level is discussed.  相似文献   

Field and laboratory observations on predation and prey selectivity of the scyphomedusa Chrysaora cf. caliparea in Southeast Indian waters     

André C. Morandini 《中国海洋大学学报(英文版)》2011,10(1):47-54

Chrysaora cf. caliparea, one of the most abundant medusae species in India, seems to be an important predator in the coastal waters of Bay of Bengal. The ability of Chrysaora cf. caliparea to feed at maximum rate in high prey concentrations implies that this jellyfish can efficiently exploit dense prey patches, at least for a short period. This study presents preliminary information regarding digestion and feeding rate upon copepods in a warm water environment. The ingestion rate of the average-sized medusae Chrysaora cf. caliparea is well balanced in nature, which in turn implies that this jellyfish is tuned for optimal utilization of available prey resources. Comparison with earlier research indicates that prey escape speed is one important factor governing which prey will be captured. A full understanding of predation mechanics awaits further investigation of both predator and prey behavior. However, because of the scarcity of long-term quantitative population data most insights have to be made indirectly. Nevertheless, low abundance of Chrysaora cf. caliparea in the water column during summer (May 2007) and the overall annual abundance seem not to considerably affect the zooplankton population, especially copepods. The present work contributes to the knowledge of prey-predator relationship of the forgotten fauna in Indian waters, which is especially crucial for understanding the process of ecological recovery of coastal water environment.  相似文献   

Undermining the science or undermining Nature?     

Bellie Sivakumar 《水文研究》2008,22(6):893-897

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Experimental and analytical model studies on leachate volume computation from solid waste     

D. Sivakumar 《International Journal of Environmental Science and Technology》2013,10(5):903-916

An extensive use of solid-waste landfills for disposal of municipal and industrial wastes have prompted increased attention to groundwater pollution caused by leachate generated in such landfills. The potential for groundwater contamination by leachate has necessitated engineering designs for landfills. The quantity of leachate generated from the solid waste and the movement of water through the solid waste depends on water input and the solid-waste characteristics. This paper dealt with the experimental investigations using the laboratory solid-waste leaching column to estimate the total leachate volume/leachate flow for unsaturated and saturated conditions. The hydraulic properties of the solid waste like initial moisture content, field capacity, permanent wilting point, saturation moisture content, effective void ratio, saturation hydraulic conductivity and saturation suction pressure were determined from the small-scale laboratory experiments, which are the input for analytical model study of leachate flow/total leachate volume for both unsaturated and saturated conditions. The result of analytical model study was compared with the results of experimental investigations. Comparisons of measured and computed total leachate volume/leachate flow using Darcy’s law showed reasonable agreement.  相似文献