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New Delhi, India

Maiti S.,Indian Institute of Technology Roorkee | Maiti S.,CSIR - Central Electrochemical Research Institute | Mishra I.M.,Indian Institute of Technology Roorkee | Bhattacharya S.D.,Indian Institute of Technology Roorkee | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

The present study reports the removal of oil from oil-in-water (o/w) emulsion using a commercial resin which is a co-polymer of styrene and di-vinyl benzene. The stability of the 0.05% (w/w) o/w emulsion was investigated for different surfactant concentrations (0.25-4%), mixing time (5-60min) and stirring rate (500-2500rpm). The emulsion stability was estimated by measuring the relative volume of emulsion after 24h of the preparation of emulsion and the zeta potential. 1% of surfactant, 18min of mixing time and 2000rpm stirring were found to be the optimum conditions for the most stable emulsions. A series of experiments were performed to investigate the effect of such parameters as influent oil concentration (30-500mg/dm3), bed height (30-100mm) and flow rate (10-20dm3/h) on the oil removal efficiency of the resin. More than 89% of emulsified oil was removed under optimal operating conditions: 10dm3/h flow velocity, 75mm bed height, and 500mg/dm3 influent concentration of oil in the o/w emulsion. SEM and FTIR results indicate that the hydrogen bonding and hydrophilic interaction were the principal driving forces for the adhesion of oil onto the polymeric resin surfaces. The results indicated that the resin is very effective in removing oil from o/w emulsion. © 2011 Elsevier B.V. Source

Most of the past theoretical works with the rotating ring disk electrode (RRDE) system have been restricted to situations where supporting electrolyte concentration is large enough so that the effects of migration of ionic species in the solution becomes negligible. In this work, effects of ionic migration have been investigated for a RRDE system by solving the differential equations describing mass transfer in presence of ionic migration using numerical technique. Two cases were considered for simulation, presence and absence of migration of ionic species. Results indicate that in presence of migration, collection efficiency of a RRDE system increases for all electrode geometries and concentration boundary layer thickness reduces. Results also indicate that collection efficiency is dependent on electrode geometries. The system chosen for simulation is copper sulfate solution of 0.1 (M) concentration with little supporting electrolyte. It is also noticed that migration effect remains important for supporting electrolyte concentration as high as 0.1 (M). Limiting current condition was assumed. © 2012 American Institute of Chemical Engineers (AIChE). Source

Jain S.K.,Jaypee University of Information Technology | Nanda A.,Engineers India Ltd
Mechanics of Advanced Materials and Structures | Year: 2010

The paper presents a viscoplastic formulation including damage for creep and creep rupture. The model incorporates a damage evolution law which includes both the viscoplastic strain rate as well as stress rate. Primary, secondary and tertiary creep are incorporated in this formulation. Model parameters are obtained for polycarbonate using both creep test and the constant strain rate test data. It is found that the model can give a reasonable predictions for creep and creep rupture. However the model will need to be modified for the constant strain rate case. The paper also presents a multi-axial formulation for the model. The formulation is general enough so we will be able to apply it to a complex problem of landslides in soil masses which is stated in the paper as our plan for future research. Copyright © Taylor & Francis Group, LLC. Source

Usmani A.,Engineers India Ltd | Ramana G.V.,Indian Institute of Technology Delhi | Sharma K.G.,Indian Institute of Technology Delhi
International Journal of Geomechanics | Year: 2012

This study investigates the drained stress-strain-volume change behavior of Delhi silt under triaxial compression and extension loading conditions using two different existing constitutive models, the hardening soil (HS) model and a hierarchical single surface (HISS) model. The HISS model is shown to be able to capture the stress-strain-volumetric response in both compression and extension loadings with higher accuracy as compared with the HS model. © 2012 American Society of Civil Engineers. Source

Usmani A.,Engineers India Ltd
Electronic Journal of Geotechnical Engineering | Year: 2013

Buffer storage of crude oil in large underground unlined rock caverns is one of the economical alternatives to ensure energy security of import dependent countries. Principle of storage essentially employs ground water pressure for containing the product within an unlined rock cavern. Initial site investigation campaign carried out involving geological, geophysical, geo-technical and hydro-geological investigations, establishes competency of rock formations in conjunction with ground water conditions for construction of unlined rock caverns. In such projects, engineering geology forms an important aspect not only during the initial feasibility stage of the project, but also in subsequent execution phase, wherein unlined rock caverns are built by conventional drill and blast technique. Design of underground structures exhibit lot of uncertainties in their basic approach and require an active and dynamic design intervention during construction progress. In this context predictive geological model is developed based on initial investigation results, which is continuously updated as the excavation progresses through stages of heading and benches. As part of this modeling exercise, critical segments of the caverns are identified as geological hotspot which undergoes additional stability analysis before excavation in order to take necessary counteractive steps. This approach based on pro-active construction methodology, helps to ensure preparedness to address the rock mechanical aspects of the identified segments, thus results in a reduced risk exposure. The study outlines, the process of identification and approach adopted to treat geological hotspots encountered during excavation for large underground rock caverns. © 2013, EJGE. Source

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