Dielectric and Ferroelectric Properties of Ceramics in the Pb(Zn 1/3Nb2/3)O3-BaTiO3-PbTiO3 System

The use of Pb(Zn_1/3Nb_2/3)O₃ ceramics is restricted by the formation of a pyrochlore phase detrimental to both dielectric and piezoelectric properties. Recently it has been shown that a 6 mol% addition of BaTiO₃ to PZN suppresses the formation of pyrochlore phase. Phase relations and dielectric properties of ceramics in the PZN-BT-PT system are reported here. Compositions with the perovskite structure, having high dielectric constant and low temperature coefficient of capacitance, have been identified.     

OPTIMIZATION OF KREIS TEST FOR EDIBLE OILS

Quality evaluation of edible oils is tested by different methods. Among the chemical methods, Kreis test is a promising one for early detection of rancidity, particularly aldehydes with a characteristic odor impact. Positive relationship of these breakdown products with perceived deterioration in quality evoked interest in re-examining the Kreis test. The color development in the test is critical and requires optimization. In continuation of studies in edible oils, the present investigation deals with sunflower and mustard oils. Through central composite rotatable design, response surface was fit as a function of oil quantity (0.3–3.3 mL) 1% phloroglucinol (0.08 mol) in acetic acid (0.3–3.3 mL) and incubation period (10–90 min). The polynomial fits were excellent with multiple correlation of >0.90. Optimized conditions were obtained for the two oils. Thus, use of 1 mL oil, 1 mL of 1% phloroglucinol, incubation time of 20 min and absorbance readings at 545 nm is derived and found applicable to all edible oils for routine tests.     

Raman spectra of Bi–Sr–Ca–Cu–O high temperature superconductors

Two high-temperature superconducting BiSrCaCuO compounds were fabricated as Bi_2.1Sr₄Ca₄Cu₃O_10+δ and Bi₂Sr₂Ca₂Cu₃O_10+δ. The X-ray diffraction patterns of both the compounds show that Bi_2.1Sr₄Ca₄Cu₃O_10+δ contains predominantly the high T_c 2223 phase, and Bi₂Sr₂Ca₂Cu₃O_10+δ the low T_c 2212 and high T_c 2223 phases, in equal amounts. The Raman spectra of these samples exhibit broad bands in the 430–512 cm^-1 region, as in the lead-substituted 2212 phase. Change in configuration due to the presence of the 2223 phase in the sample is indicated by the broadening of the 465 cm^-1 line. New bands at 611 and 678 cm^-1 are observed. Peaks in the 430–512 cm^-1 region exhibit a softening when the temperature is reduced to 93 K. This revised version was published online in November 2006 with corrections to the Cover Date.     

SWELLING STRESS AND HYDROSTATIC COMPRESSIBILITY OF GROUND CORN AND ITS CONSTITUENTS

Swelling stresses and hydrostatic compressibilities of ground whole corn, endosperm and germ were determined by using the theory of swelling stresses in gels. The ground corn and its constituents were considered as gels. The magnitude of swelling stresses in the ground corn materials was in order of several thousand pounds per square inch at low equilibrium moisture contents, when subjected to increased vapor pressure. The hydrostatic compressibility for ground whole corn, endosperm and germ increased with an increase of moisture content.     

New approach for solving intuitionistic fuzzy multi-objective transportation problem

Multi-objective transportation problem (MOTP) under intuitionistic fuzzy (IF) environment is analysed in this paper. Due to the fluctuation of market scenario, we assume that the transportation cost, the supply and the demand parameters are not always precise. Hence, the parameters are imprecise, i.e., they are IF numbers. Considering the specific cut interval, the IF transportation cost matrix is converted to interval cost matrix in our proposed problem. Again, using the same concept, the IF supply and the IF demand of the MOTP are reduced to the interval form. Then the proposed MOTP is changed into the deterministic MOTP, which includes interval form of the objective functions. Two approaches, namely intuitionistic fuzzy programming and goal programming, are used to derive the optimal solutions of our proposed problem, and then the optimal solutions are compared. A numerical example is included to illustrate the feasibility and the applicability of the proposed problem. Finally, we present the conclusions with the future scopes of our study.     

Finite element analysis of stress–strain localization and distribution in Al-4.5Cu-2Mg alloy

Finite element analysis has been carried out to understand the effect of various processing routes and condition on the microscale deformation behavior of Al-4.5Cu-2Mg alloy. The alloy has been developed through four different routes and condition, i.e. conventional gravity casting with and without refiner, rheocasting and SIMA process. The optical microstructures of the alloy have been used to develop representative volume elements (RVEs). Two different boundary conditions have been employed to simulate the deformation behavior of the alloy under uniaxial loading. Finally, the simulated stress–strain behavior of the alloy is compared with the experimental result. It is found that the microstructural morphology has a significant impact on stress and strain distribution and load carrying capacity. The eutectic phase always carries a higher load than the α(Al) phase. The globular α(Al) grains with thinner and uniformly distributed eutectic network provide a better stress and strain distribution. Owing to this, SIMA processed alloy has better stress and strain distribution than other processes. Finally, the simulated yield strength of the alloy is verified by experiment and they have great agreement.     

Effect of capping agents on optical and antibacterial properties of cadmium selenide quantum dots

Cadmium selenide quantum dots (CdSe QDs) were synthesized in aqueous phase by the freezing temperature injection technique using different capping agents (viz. thioglycolic acid, 1-thioglycerol, L-cysteine). Absorption spectra of CdSe QDs exhibited a blue shift as compared to its bulk counterpart, which is an indication of quantum confinement effect. The photoluminescence spectra of CdSe QDs confirmed that the particles are poly-dispersed and possess enhanced luminescent property, depending upon the chemical nature of capping agents. The QDs have been characterized by Fourier-transform infrared spectroscopy, atomic absorption spectroscopy and transmission electron microscopy. Further, antimicrobial activity of as-prepared QDs has also been investigated using the disk diffusion method.     

INFLUENCE OF SAMPLE SIZE AND SHAPE ON TRANSPORT PARAMETERS DURING DRYING OF SHRINKING BODIES

An experimental investigation on the influence of sample size and shape on heat and mass transport parameters under natural convection air‐drying is presented. Potato cylinders with length of 0.05 m and thicknesses of 0.005, 0.008, 0.010 and 0.016 m, and circular slices with diameter of 0.05 m and thickness of 0.01 m were dried in a laboratory scale hot‐air cabinet dryer. Results indicate that each transport parameter exhibits a linear relationship with sample thickness. Convective heat and mass transfer coefficients (h_cand h_m) decreased whereas moisture diffusion coefficient (D_eff) increased with increasing thickness. Considering no sample shrinkage effect in the parameter analysis, for the thickness range considered, the values of h_care found to be underestimated in the range of 29.0–30.6%, whereas those of h_mand D_eff are overestimated in the range of 33.7–38.0% and 75.9–128.1%, respectively. Using Levenberg–Marquardt algorithm for optimization, a correlation for Biot number for mass transfer (Bi_m) as a function of drying time and sample thickness is proposed. A close agreement was observed between dimensionless moisture contents predicted by this relation and those obtained from experiments for different sample thicknesses at drying air temperature of 60C. For the same thickness and drying conditions, circular slices caused an increase in each transport parameter significantly.