Parametric analysis of surfactant-aided imbibition in fractured carbonates

Many carbonate oil reservoirs are oil-wet and fractured; waterflood recovery is very low. Dilute surfactant solution injection into the fractures can improve oil production from the matrix by altering the wettability of the rock to a water-wetting state. A 2D, two-phase, multicomponent, finite-volume, fully-implicit numerical simulator calibrated with our laboratory results is used to assess the sensitivity of the process to wettability alteration, IFT reduction, oil viscosity, surfactant diffusivity, matrix block dimensions, and permeability heterogeneity. Capillarity drives the oil production at the early stage, but gravity is the major driving force afterwards. Surfactants which alter the wettability to a water-wet regime give higher recovery rates for higher IFT systems. Surfactants which cannot alter wettability give higher recovery for lower IFT systems. As the wettability alteration increases the rate of oil recovery increases. Recovery rate decreases with permeability significantly for a low tension system, but only mildly for high tension systems. Increasing the block dimensions and increasing oil viscosity decreases the rate of oil recovery and is in accordance with the scaling group for a gravity driven process. Heterogeneous layers in a porous medium can increase or decrease the rate of oil recovery depending on the permeability and the aspect ratio of the matrix block.     

Facile synthesis methodology and characterization studies of silica-decorated hybridized anisotropic nanotubes and nanosheets

Carbonaceous nanomaterials and their derivatives have been inspired tremendous enthusiasm in the scientific community. They have been excogitated as the encouraging attributes and the qualified dispersed phase to develop multi-functional composites. Particularly, graphene and carbon nanotube (anisotropic fillers) have gained substantial research interest owing to their promising characteristics. This highlights an innovative technique to synthesize hybridized nanotube and nanosheet. Initially, parent materials have been synthesized: The pristine CNT has been modified by acid mixture solution, and reduced graphene oxide has been prepared by chemical reduction method. Henceforth, the self-assembly in situ sol–gel technique has been endorsed here. The synthesized nanohybrids have been characterized by different spectroscopic techniques: FTIR, Raman, UV, and XPS to confirm the attachment of multifunctionalities; meanwhile, the composition and stability have been investigated from XRD and TGA plots. The magnitude of surface charge and particle size distribution have been evaluated for the parent and hybridized products; further, morphology of all the samples has been authenticated from FESEM and TEM.     

Inverse acoustical characterization of natural jute sound absorbing material by the particle swarm optimization method

For modeling of jute as acoustic material, knowledge of its non-acoustical parameters like porosity, tortuosity, air flow resistivity, thermal and viscous characteristic lengths is a prime requisite. Measurement of these non-acoustical parameters is not straightforward and involves a dedicated measurement setup. So in order to overcome this issue, the inverse acoustical characterization can be used. In this paper, the particle swarm optimization method (PSO) is used as an optimization method. This method estimates the non-acoustical parameters of jute material in felt form by minimizing the error between experimental and theoretical sound absorption data. In this work, the impedance prediction models for fibrous materials like Johnson–Champoux–Allard model with rigid and limp frame and Garai–Pompoli model is used for sound absorption coefficient calculation by the transfer matrix method along with the PSO. The inverse estimated non-acoustical parameters for jute material are then compared with estimated and experimentally measured parameters for jute felts. Using these inversely predicted parameters, sound absorption of multilayer sound absorbers is also studied.     

Effect of the headgroup structure on the aggregation behavior and stability of self-assemblies of sodium N-[4-(n-dodecyloxy)benzoyl]-l-aminoacidates in water

Three amino acid-derived chiral surfactants, sodium N-[4-(n-dodecyloxy)benzoyl]-L-leucinate (SDBL), sodium N-[4-(n-dodecyloxy)benzoyl]-L-isoleucinate (SDBIL), and sodium N-[4-(n-dodecyloxy)benzoyl]-L-threoninate (SDBT), were synthesized, and their aggregation behavior was studied in aqueous solution. Surface tension, fluorescence probe, dynamic light scattering, nuclear magnetic resonance (NMR), gel permeation chromatography, circular dichroism, and optical as well as transmission electron microscopic techniques were utilized to characterize the self-assemblies formed by the amphiphiles. Results of these studies reveal that the surfactants have a very low critical aggregation concentration (cac) and they form spherical vesicles spontaneously in dilute aqueous solution. The mean diameters of the vesicles were measured to be in the range of 130-190 nm. 1H NMR spectra indicated hydrogen bonding between the amide groups near the surfactant headgroup, which is one of the driving forces for vesicle formation. The vesicle formation is more favored at a pH of about 7.0. The amphiphiles also form chiral helical aggregates at relatively higher concentrations as indicated by circular dichroism spectra. The stability of the vesicles was also evaluated with respect to the surfactant concentration, pH, temperature, and aging. The vesicles have a tendency to transform into elongated vesicles (closed tubules) or rodlike micelles with an increase of the surfactant concentration and/or pH. On the basis of the results obtained from different studies, phase diagrams for all three water/amphiphile systems have been constructed. The studies have further shown that the stereogenic center at the amino acid side chain has a significant effect on the aggregation properties of the amphiphiles and on the stability of the self-assemblies.     

Multiple ionization of argon in coincidence with projectile ions in 60–120 MeV Si q+-Ar collisions

A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer processes in collisions of 60–120 MeV Si ^q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization, electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated. The data reported on the present collision system result from a direct measurement in the considered impact energy for the first time. The total ionization cross-sections for the recoil ions are shown to scale as q ^1.7/E _p ^0.5 , where E _p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j ² upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing cross-sections σ _qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow our data for different ionization processes is reviewed and discussed.     

Fabrication and characterization of enhanced hydrazine electrochemical sensor based on gold nanoparticles decorated on the vanadium oxide,ruthenium oxide nanomaterials,and carbon nanotubes composites

This work describes the synthesis of mixed oxide film of vanadium and ruthenium by pulsed deposition technique on multiwall carbon nanotubes and the decoration of gold nanoparticles on the mixed film. A ternary electrocatalyst has been developed for the electrochemical oxidation of hydrazine by combining two metal oxide mixtures with Au nanoparticles. Surface morphology and chemical composition of the electrode have been examined with SEM, EDX, HRTEM, EIS, and XRD. The peak current of hydrazine increased 9 times at the AuNPs/(VOx-RuOx)/CNT/GCE compared to the bare GCE, and the peak potential shifted to negative 848 mV. Linear sweep voltammetry (LSV) and amperometric techniques revealed that the AuNPs/(VOx-RuOx)/CNT/GCE displays linear concentration range 2.5–10000 µM (LSV) and the concentration range 0.03–100 µM (amperometry). The limit of detection (LOD) is 0.5 μM and 0.1 μM at (S/N = 3) for LSV and amperometric technique, respectively. The results obtained show a good RSD% of 2.1%–3.2% and reasonable recovery of 97%–108% of hydrazine detection.     

Λ b →Λ c +a 1 decay in the heavy quark effective theory

Using the heavy quark approximation, we have studied the nonleptonic decay mode Λ _b →Λ _c a ₁. We have included nonfactorizable contributions as well as factorizable ones in our analysis. The estimated branching ratio for this process is (1.4±0.1)% and the asymmetry parameter α found to be −0.8.     

Integrated Condition Monitoring of Large Captive Power Plants and Aluminum Smelters

Condition monitoring is implementation of the advanced diagnostic techniques to reduce downtime and to increase the efficiency and reliability. The research is for determining the usage of advanced techniques like Vibration analysis, Oil analysis and Thermography to diagnose ensuing problems of the Plant and Machinery at an early stage and plan to take corrective and preventive actions to eliminate the forthcoming breakdown and enhancing the reliability of the system. Nowadays, the most of the industries have adopted the condition monitoring techniques as a part of support system to the basic maintenance strategies. Major condition monitoring technique they follow is Vibration Spectrum Analysis, which can detect faults at a very early stage. However implementation of other techniques like Oil analysis or Ferrography, Thermography etc. can further enhance the data interpretation as they would detect the source of abnormality at much early stage thus providing us with a longer lead time to plan and take the corrective actions. In Large Captive Power Plants and Aluminium Smelters, Integrated Condition Monitoring techniques play an important role as stoppage of primary system and its auxiliaries (boiler, steam turbine, generator, coal and ash handling plants etc.) results into the stoppage of the entire plant, which in turn leads to loss of productivity. From economical and operational point of view, it is desirable to ensure optimum level of system availability.