An EPQ model with promotional demand in random planning horizon: population varying genetic algorithm approach

One of the economic production quantity problems that have been of interest to researchers is the production with reworking of the imperfect items including waste most disposal form and vending the units. The available models in the literature assumed that the decay rate of the items is satisfied from three different points of view: (i) minimum demands of the customer’s requirement, (ii) demands to be enhanced for lower selling price and (iii) demands of the customers who are motivated by the advertisement. The model is developed over a finite random planning horizon, which is assumed to follow the exponential distribution with known parameters. The model has been illustrated with a numerical example, whose parametric inputs are estimated from market survey. Here the model is optimized by using a population varying genetic algorithm.     

Hydraulic resistance of rigid polyurethane foams. II. Effect of variation of surfactant,water, and nucleating agent concentrations on foam structure and properties

Hydraulic resistance of rigid polyurethane foams to penetration by water at high pressures is studied in this work in the context of buoyancy applications. Micron sized silica particles are used as nucleating agents. The effect of the variation of the concentrations of the surfactant, water, and nucleating agent on cell structure, closed cell content, and compressive modulus, is examined. Foams have densities in the range of 145 to 165 kg/m³. At a particular water concentration, with increase in the concentration of the surfactant, the window area of the cells becomes smaller and the hydraulic resistance of the foam increases. A cell window is the lamella of the foam material that separates two adjacent cells. With increase in the concentration of water keeping surfactant concentration constant, the average window area remains almost the same but the cell window area distribution becomes wider and the hydraulic resistance of the foams decreases. Foams made with silica have smaller cell windows but lower hydraulic resistance than that of the foams made without silica. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2830–2837, 2004     

Synthesis and Structural Investigation of Foldamer-Based Iodine-Supported Artificial Glycosidases

Glycosidases are a type of enzyme that hydrolytically cleave carbohydrates and form glycans for biologically important processes. The inadequacies of glycosidases or their genetic abnormalities are responsible for various diseases. Thus, the development of glycosidase mimetics is of great importance. We have designed and synthesized an enzyme mimetic containing l -phenylalanine, α-aminoisobutyric acid (Aib), l -leucine, and m-Nifedipine. From X-ray crystallography, the foldamer adopts a β-hairpin conformation stabilized by two 10-member and one 18-member NH⋅⋅⋅O=C hydrogen bonds. Moreover, the foldamer was found to be highly efficient in hydrolysing ethers and glycosides in the presence of iodine at room temperature. Further, X-ray analysis shows the backbone conformation of the enzyme mimetic to be almost unchanged after the glycosidase reaction. This is the first example of iodine-supported artificial glycosidase activity with an enzyme mimic at ambient conditions.     

Studies of extraction of methylene blue from synthetic waste water using liquid emulsion membrane technology

A comprehensive study pertaining to liquid emulsion membrane (LEM) extraction process of methylene blue from wastewater is presented. The liquid membrane is made of an emulsifying agent (Monumal 80) with various organic diluents. Surfactant (5 wt%) (Monumal 80) and kerosene gave good extraction. Important variables affecting LEM permeation process include stability of membrane, contact time of extraction, strip phase concentration, treat ratio (strip phase: organic phase), stirring speed, feed phase concentration were systematically studied for percentage of extraction by LEM. Kerosene as diluent gave 99.57% extraction with NaOH as strip phase. © 2012 Canadian Society for Chemical Engineering     

Enhanced Activation Energy of Crystallization of Pure Zirconia Nanopowders Prepared via an Efficient Way of Synthesis Using NaBH4

An efficient way through borohydride synthesis route using NaBH₄ was performed to prepare pure zirconia nanopowders via three different conditions such as gelation, precipitation, and constant pH. Zirconia powders prepared through constant pH route show highest activation energy of crystallization (E_a = 260 kJ/mol) or higher exothermic peak temperature (717°C), when compared with gelation or precipitation route due to its controlled growth of smaller crystallites. The released huge amount of H₂ gas bubbles during borohydride synthesis via constant pH route play a major role for formation of loose smaller crystallites and thus enhances the activation energy of crystallization of pure zirconia. So, the as‐prepared zirconia powders prepared through constant pH route remain amorphous up to 600°C and pure t‐ZrO₂ (~20 nm) was stable up to 800°C.     

Effect of PES on the morphology and properties of proton conducting blends with sulfonated poly(ether ether ketone)

Development of alternate materials to Nafion, based on ionically conducting polymers and their blends is important for the wider applications of proton exchange membrane fuel cells. In this work, blends of sulfonated poly(ether ether ketone) (SPEEK) with poly(ether sulfone) (PES) are investigated. SPEEK with various ion exchange capacity (IEC) was prepared and blended with PES, which is nonionic and hydrophobic in nature. A comparative study of the water uptake, proton conductivity, and thermo‐mechanical characteristics of SPEEK and the blend membranes as a function of the IEC is presented. Addition of PES decreases the water uptake and conductivity of SPEEK. Chemical and thermal stability and mechanical properties of the membrane improve with the addition of PES. The effect of water content on the thermo‐mechanical properties of membranes was also studied. The morphology of blend membranes was studied using SEM to understand the microstructure and miscibility of the components. On the basis of the results, a plausible microstructure of the blends is presented, and is shown to be useful in understanding the variation of different properties with blending. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of Film Casting Condition and Thermal Treatment on Order Structure of Polyurethane Block Copolymer

An attempt has been made to investigate the influence of film casting temperature and thermal ageing on order structure formation of segmented polyurethane (SPU) block copolymer. For this purpose films were casted at three different temperature of 60, 80, or 100°C and thermal aged at 100, 120, 130, or 150°C. The structure of films were investigated by Fourier-transform infrared (FT-IR), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Film casted at slow solvent evaporation has more regular structure than the film casted at rapid solvent evaporation. Crystaline structure decreases with increase in casting temperature due to chain entanglement, which makes crystallization process tougher. The effect of ageing temperature on crystalline structure formation remains unclear. Decrease of ordered structure was observed when the samples were heat treated at 100 or 120°C, however, slight increase of ordered structures were observed for the samples heat treated at 130 or 150°C. Therefore, the influence of thermal ageing has been explained in terms of order-disorder temperature of block copolymer.     

Small amphiphilic organics, coordination extended solids, and constant curvature structures

In this Account, we explore the role constant curvature structures play in amphiphilic small molecule crystals and extended coordination solids. A constant curvature structure is one in which there is a surface or interface that has the same curvature throughout its surface. Simple examples of such structures contain spheres (micelles), columns, or layers. Yet another family are cubic as is found in the gyroid topology. For amphiphilic systems, there are two domains, one generally hydrophobic and the other hydrophilic. We find that the interfaces between these two domains in small molecule structures resemble those in larger scale systems and adopt topologies related to constant curvature structures. The hydrophobic-to-total volume ratio, a molecular parameter, can be used to predict which type of constant curvature structure is adopted. In the case of three coordinate extended solids, constant curvature plays a role both in the extended net topology and in the hydrophobic-to-hydrophilic interface.     

Mixing characteristics for the single and air-water two-phase flows in miniaturized parallel multichannel-based devices

Investigation on the miniaturized parallel multichannel-based devices packed with glass beads to improve the mass exchange execution is the critical focal point of the current study. One of the essential parameters to specify the miniaturized devices' flow distribution is the residence time distribution (RTD). In the present context, the RTDs of a liquid tracer were investigated for the air-water multiphase flows (concurrent) across the multichannel-based miniaturized devices (comprising of 11 similar dimensional parallel channels). The devices were variable in height and packed with glass beads. The conductivity estimations generated the RTD curves and were addressed by the axial dispersion model (ADM). The fluid-flow rates differed within the range of 5–23 ml min⁻¹. The axial dispersion coefficients and the rate of the specific energy dispersion were investigated. The effects of pressure difference and geometry on the hydrodynamic attributes and mixing properties were well-illustrated, and the new correlations were suggested.     

MCD Approach for Assessing the Optimal Operating Condition during Sliding Wear Characteristics of LM25/SiC AMCs Processed by an Improved Stir Casting Technique

Silicon - The Sliding wear behaviour of the improved stir cast LM25/SiC composite was investigated using a wear apparatus having pin-on-disc configuration. The tests were conducted at varying...