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Big data comprises voluminous and heterogeneous data that has a limited level of trustworthiness. This data is used to generate valuable information that can be used for decision making. However, decision making queries on Big data consume a lot of time for processing resulting in higher response times. For effective and efficient decision making, this response time needs to be reduced. View materialization has been used successfully to reduce the query response time in the context of a data warehouse. Selection of such views is a complex problem vis-à-vis Big data and is the focus of this paper. In this paper, the Big data view selection problem is formulated as a bi-objective optimization problem with the two objectives being the minimization of the query evaluation cost and the minimization of the update processing cost. Accordingly, a Big data view selection algorithm that selects Big data views for a given query workload, using the vector evaluated genetic algorithm, is proposed. The proposed algorithm aims to generate views that are able to reduce the response time of decision-making queries.

Surfactants for enhanced oil recovery are important to study due to their special characteristics like foam generation, lowering interfacial tension between oleic and aqueous phases, and wettability alteration of reservoir rock surfaces. Foam is a good mobility control agent in enhanced oil recovery for improving the mobility ratio. In the present work, the foaming behavior of three nonionic ethoxylated surfactants, namely Tergitol 15-S-7, Tergitol 15-S-9, and Tergitol 15-S-12, was studied experimentally. Among the surfactants, Tergitol 15-S-12 shows the highest foamability. The effect of NaCl concentration and synthetic seawater on foaming behavior of the surfactants was investigated by the test-tube shaking method. The critical micelle concentrations of aqueous solutions of the different nonionic surfactants were measured at 300 K. It was found that the critical micelle concentrations of all surfactants also increased with increasing ethylene oxide number. Dynamic light scattering experiments were performed to investigate the micelle sizes of the surfactants at their respective critical micelle concentrations. Core flooding experiments were carried out in sand packs using the surfactant solutions. It was found that 22% additional oil was recovered in the case of all the surfactants over secondary water flooding. Tergitol 15-S-12 exhibited the maximum additional oil recovery which is more than 26% after water injection.

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Fatty acid mono‐ and diesters of diglycerol constitute the major portion of commercial polyglycerol esters; hence, their composition influences the performance of the latter as emulsifiers. The correlation of structure of the fatty acids in the mono‐ and diesters with surfactant properties is of interest. Linear diglycerol was isolated from polymerized glycerol by acetonation, fractional distillation and regeneration. Diglycerol mono‐ and diesters of undecenoic, lauric, stearic, oleic and ricinoleic acids were prepared by reacting diglycerol and fatty acids in a refluxing mixture of acetonitrile‐tetrahydrofuran (75:25) in the presence of p‐toluenesulfonic acid and molecular sieves. Mono‐ and diesters were separated by silica gel column chromatography, and their purities were ascertained by thin layer chromatography and determination of saponification value. The structures were confirmed by periodic acid oxidation, chemical‐ionization mass spectrometry and 13 C‐NMR spectroscopy. Surfactant properties of the esters were determined. Monoesters showed higher ability in surface tension reduction, emulsification and foaming than the diesters. Short‐chain fatty acid esters showed better surfactant properties than the long‐chain fatty acid esters. The presence of a central double bond in the lipophilic part of the monoesters reduced emulsion stability. The presence of a hydroxy group in acyl chain retarded foaming and surface tension reducing power.