Particle size effects in flash sintering

The study of 3 mol% yttria stabilized zirconia (3YSZ) with different particle sizes provides new insights into flash sintering. Four powders, all with the same crystallite size but various particle size were investigated: described as nominally 1 μm (D80 = 0.51 μm, meaning 80 vol% has a size less than 0.51 μm), 2 μm (D80 = 0.90 μm), 5 μm (D80 = 2.11 μm) and 10 μm (D80 = 3.09 μm). While the furnace temperature for flash sintering, at a field of 100 V cm^?1, increased from 920 °C to 1040 °C with particle size, the specimen temperature in all instances remained at ～1200 °C. The quantum increase in density decreased with larger particles. The grain size distribution of conventionally and flash sintered specimens remained similar, with some evidence of a preponderance of nanograins in the flash sintered specimens. Joule heating was well below the temperatures that would have been required for sintering in a few seconds. An explanation based upon the nucleation of Frenkel pairs is proposed.     

Effect of Cold Rolling and Heat Treatment on Microstructure and Mechanical Properties of Ti-4Al-1Mn Titanium Alloy

Mechanical behavior of Ti-4Al-1Mn titanium alloy has been studied in annealed, cold-rolled and heat-treated conditions. Room temperature tensile strength as well as % elongation has been found to be low with increasing amount of cold rolling. Lowering of strength in cold worked condition is attributed to premature failure. However, the same has been mitigated after heat treatment. Significant effect of cooling media (air and water) from heat treatment temperature on microstructure was not found except for the degree of fineness of α plates. Optimum properties (strength as well as ductility) were exhibited by samples subjected to 15% cold rolling and heat treatment below β transus temperature, which can be attributed to presence of recrystallized microstructure. In cold worked condition, the microstructure shows fine fragmented α plates/Widmanstätten morphology with high dislocation density along with a large amount of strain fields and twinning, which gets transformed to recrystallized equiaxed microstructure and with plate-like morphology after near β heat treatment. Prior cold work is found to have a significant effect on mechanical properties supported by evolution of microstructure. Twinning is found to be assisting in deformation as well as in recrystallization through the formation of deformation and annealing twins during cold working and heat treatment. Fracture analysis of the tested sample with prior cold work and heat-treated condition revealed quasi-ductile failure as compared to only ductile failure features seen for samples heat treated without prior cold work.     

Sliding mode control of quadruple tank process

The process investigated herein is the quadruple tank system that is stable only within a limited zone of operating parameters. The process model has been developed from fundamentals and tuned with experimental data. A controller design based on feedback linearization has been tested on this process model. Coupling feedback linearization with sliding mode algorithm provides robust control of the process and performs far superior to conventional PI control. A PC based controller interfaced to the experimental quadruple tank experimental set up has been used to implement this algorithm and test its performance. Inserting a ‘boundary layer’ around the sliding surface reduced the ‘chattering’ associated with sliding mode control. The implemented controller provides robust control and excellent set point tracking.     

Viscous Potential Flow Analysis of Nonlinear Rayleigh–Taylor Instability with Heat and Mass Transfer

The nonlinear analysis of Rayleigh?CTaylor instability of two viscous fluids is studied when there is heat and mass transfer across the interface, using viscous potential flow theory. The fluids are considered to be viscous and incompressible with different kinematic viscosities. The analysis is based on the method of multiple scale perturbation and the nonlinear stability is governed by first-order nonlinear partial differential equation. The stability conditions are obtained and stability is discussed theoretically as well as numerically. Regions of stability and instability have been shown graphically indicating the effect of various parameters. It has been observed that the heat and mass transfer has stabilizing effect on the stability of the system in the nonlinear analysis.     

Magnetic-nanoparticle-doped carbogenic nanocomposite: an effective magnetic resonance/fluorescence multimodal imaging probe

A novel and facile approach is developed to synthesize a magnetic nanoparticle (iron oxide)-doped carbogenic nanocomposite (IO-CNC) for magnetic resonance (MR)/fluorescence imaging applications. IO-CNC is synthesized by thermal decomposition of organic precursors in the presence of Fe(3) O(4) nanoparticles with an average size of 6 nm. IO-CNC shows wavelength-tunable fluorescence properties with high quantum yield. Magnetic studies confirm the superparamagnetic nature of IO-CNC at room temperature. IO-CNC shows MR contrast behavior by affecting the proton relaxation phenomena. The measured longitudinal (r(1) ) and transverse (r(2) ) relaxivity values are 4.52 and 34.75 mM(-1) s(-1) , respectively. No apparent cytotoxicity is observed and the nanocomposite shows a biocompatible nature. In vivo MR studies show both T(1) and T(2) * contrast behavior of the nanocomposite. Fluorescence imaging indicates selective uptake of IO-CNC by macrophages in spleen.     

Survival of Streptococcus pyogenes on foods and food contact surfaces

Streptococcus pyogenes causes septic sore throat in millions of Americans each year and may be transmitted from food handlers to food contact surfaces, foods, and consumers. This study examined the individual survival of six S. pyogenes strains on food contact surfaces (plastic and ceramic plates, plastic cups, and stainless steel utensils) held at 21 degrees C for 2 h and on tomatoes stored aerobically at 21 degrees C for 2 h and at 5 degrees C for 24 h. Survival of a cocktail of the six S. pyogenes strains was also evaluated on vacuum-packaged ready-to-eat meats and cheeses held at 21 degrees C for 8 h and at 5 degrees C for 24 h. Populations generally did not change on tomatoes, cheeses, or beef bologna; however, there were small (0.1 to 0.7 log CFU) but statistically significant decreases (P < 0.05) in average S. pyogenes populations on turkey luncheon meat and beef summer sausage stored for 8 h at 21degrees C and on beef summer sausage stored for 24 h at 5 degrees C. On food contact surfaces, average populations either decreased slightly (P > or = 0.05) or remained constant, with the exception of three strains that significantly decreased in number on ceramic plates (P < 0.05; average decreases, 0.3 log CFU). Results of this study suggest the importance of preventing the contamination of foods and food contact surfaces with S. pyogenes by infected workers.     

An Analytical Solution of Vector Diffraction for Focusing Optical Systems

Abstract

Vector diffraction theory for optical systems has been of interest for a long time. Ignatovsky and Wolf have formulated these problems in terms of diffraction integrals and Wolf has presented very interesting results. Usually, the quadrature of diffraction integrals is numerically intensive, therefore these problems have remained of interest and many authors have worked on the Ignatovsky-Wolf formulation or some variation thereof. This paper presents yet another method of solving diffraction integrals. Since a certain part of the kernel of these integrals is Riemann integrable in the interval [0, π], the Weierstrass theorem says that it can be approximated by a uniformly convergent series of orthogonal functions. Thus it is possible to expand these functions into a series of Gegenbauer polynomials of the first kind. Once these expansions are substituted in the diffraction integrals, the resulting integrals are readily evaluated, over the surface of unit sphere, in terms of the spherical Bessel functions and Gegenbauer polynomials. The results are particularly simple if the image plane is the focal plane. In this paper, we evaluate the diffraction integrals for several optical systems of arbitrary numerical aperture with or without obscuration, and for a parabolic reflector. The results presented here are in agreement with previously published results. The numerical computations are easy since all the functions are evaluated by adding a finite series. The calculations which for the basis of results presented in this paper were performed on a personal computer.     

Preserving boundaries for image texture segmentation using grey level co-occurring probabilities

Texture analysis has been used extensively in the computer-assisted interpretation of digital imagery. A popular texture feature extraction approach is the grey level co-occurrence probability (GLCP) method. Most investigations consider the use of the GLCP texture features for classification purposes only, and do not address segmentation performance. Specifically, for segmentation, the pixels in an image located near texture boundaries have a tendency to be misclassified. Boundary preservation when using the GLCP texture features for image segmentation is important. An advancement which exploits spatial relationships has been implemented. The generated features are referred to as weighted GLCP (WGLCP) texture features. In addition, an investigation for selecting suitable GLCP parameters for improved boundary preservation is presented. From the tests, WGLCP features provide improved boundary preservation and segmentation accuracy at a computational cost. As well, the GLCP correlation statistical parameter should not be used when segmenting images with high contrast texture boundaries.     

Operation kinetics of a DNA-based molecular switch

The influence of temperature variation, salt concentration, and pH on the operation kinetics of a simple DNA-based molecular switch is investigated. The device shows robust behavior over a wide range of temperatures, pH, and salt concentrations. In particular, the device operates well under physiological conditions. The experimental data can be qualitatively understood in terms of the influence temperature, salt concentration, and pH have on DNA strand interactions.     

Azadirachta indica exhibits chemopreventive action against hepatic cancer: Studies on associated histopathological and ultrastructural changes

The present study was designed to evaluate the anticarcinogenic potential of Azadirachta indica against N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis. Further, the associated histopathological and ultrastructural changes were also analyzed. Hepatic cancer model was developed by the intraperitoneal administration of NDEA to mice at weekly intervals, in successive increasing doses, for a period of 8 weeks. Aqueous A. indica leaf extract (AAILE) was administered orally at a dosage of 100 μg/g body weight thrice a week till termination of the study. A relationship between histopathological grading and chemopreventive effect of A. indica had been established at various stages of carcinogenesis. Anticancer activity of A. indica was evaluated in terms of tumor incidence, tumor multiplicity, and survival rate. A significant reduction in tumor incidence (33%), tumor multiplicity (42%), and increase in survival (34%) was observed upon administration of AAILE to NDEA-abused mice. Transmission and scanning electron microscopic investigations showed severe alterations in organelle organization, cellular arrangement, degree of differentiation, cellular metabolism, and morphology of the hepatocytes. These changes appeared to be distinctly delayed upon AAILE supplementation. The results suggest A. indica may have anticancer potential against NDEA-induced hepatic cancer.