On the high-energy electron beam irradiation-induced defects in Cu2SnSe3 system: an effort towards modifying the structure,microstructure, and thermoelectric transport

Journal of Materials Science: Materials in Electronics - We present report on modulating thermoelectric transport in Cu2SnSe3 system via irradiating high-energy electrons of energy of about...     

Axisymmetric thermoelastic interactions in an unbounded body with cylindrical cavity

Summary Thermoelastic interactions in a linear, homogeneous and transversely isotropic unbounded body containing a cylindrical cavity due to a uniform step in stress or temperature applied to the boundary of the cavity are studied. A unified system of governing equations that includes among its particular cases the governing equations of the conventional and generalized thermoelasticity theories is employed. By the use of the Laplace transform technique, short time solutions for the temperature, displacement radial stress and hoop stress are constructed. The discontinuities suffered by these fields at the wavefronts are computed. Comparison with the corresponding results obtained in earlier works is made. Numerical results for a single crystal of zinc are presented.     

Minimum intensity seeking positions in polariscope set-ups

Conventional polariscope set-ups like the plane polariscope or the dark or bright field set-ups specify the positions of the various optical elements with respect to the polarising axes of the photoelastic model for determining the isoclinic and isochromatic parameters.
In this paper, it is shown that such specification is not necessary since, for any light path, the positions of the optical elements for an absolute minimum in intensity of the light emerging from the analyser are unique. To illustrate this, the case of a general retarder introducing a retardation 2δ at an azimuth θ with respect to the axis of the polariser is discussed and the conditions for the determination of the isoclinics and isochromatics are obtained.     

Extraction of rice bran oil using aqueous media

Aqueous extraction of oil from rice bran was studied on a laboratory scale and the resulting product was examined. The following process parameters influencing oil extraction were individually investigated: pH of aqueous media, extraction temperature, extraction time, agitation speed and rice bran‐to‐water ratio. Extraction temperature and pH were found to be the main factors influencing oil extraction. The highest oil yield was obtained at pH 12.0, extraction temperature 50 °C, extraction time 30 min, agitation speed 1000 rpm, and rice bran‐to‐water ratio 1.5‐to‐10. The quality of aqueous‐extracted oil in terms of free fatty acid, iodine value and saponification value was similar to a commercial sample of rice bran oil and hexane‐extracted oil, but the peroxide value was higher. Furthermore, the colour of aqueous‐extracted oil was paler than solvent‐extracted oil. © 2000 Society of Chemical Industry     

Intensifying chitin hydrolysis by adjunct treatments – an overview

Chitin is, after cellulose, the most abundant organic natural polysaccharide on Earth, being synthesized as a dominant component in the exoskeletons of crustaceans, among other sources. In the processing of seafood for human consumption, between 40 and 50% of the total raw material mass is wasted, causing a significant problem for the environment owing to its slow degradation. Efforts to find uses for chitin derivatives, particularly their oligomers, have intensified since these chemicals are highly functional and offer a wide range of applications, especially as antimicrobial agent. As a consequence, some adjunct treatments, either chemical or physical in nature, have been employed to assist acid and enzymatic hydrolysis. This work provides a detailed review of the methods employed to intensify the formation of chitin oligomers, particularly focusing on the adjunct treatments used (microwave, ultrasonication, steam explosion and gamma irradiation), and an evaluation of the yield and characteristics of the oligomers formed. Adjunct treatments are more suitable for enzymatic hydrolysis since these treatments modify the chitin structure, and enhance the hydrolysis rate and yield of the oligomers, under milder reaction conditions. For future research, it would be worth trying pre‐treatments like the application of high‐pressure to chitin in order to lower its crystallinity. © 2017 Society of Chemical Industry     

Application of orthogonal transforms in the enhancement of images in the presence of additive noise

The application of orthogonal transforms in the enfiancement of noisy images is considered. The performance of the Haar, Fourier and the Walsh-Hadamard transforms in such image enhancement is compared using simulated noisy images. Based both on subjective evaluations and a consideration of the mean square error between the original and enhanced images, the Haar transform is shown to be superior to the Fourier and Walsh-Hadamard transforms for the particular examples considered. In addition, the utility of the Haar transform is enhanced by the smaller number of computations involved in its digital implementation and lower storage requirement.     

An Analytically Stable Structure and Motion Observer Based on Monocular Vision

This paper presents a novel nonlinear sliding-mode differentiator-based complete-order observer for structure and motion identification with a calibrated monocular camera. In comparison with earlier work that requires prior knowledge of either the Euclidean geometry of the observed object or the linear acceleration of the camera and is restricted to establishing stability and convergence from image-plane measurements of a single tracked feature, the proposed scheme assumes partial velocity state feedback to asymptotically identify the true-scale Euclidean coordinates of numerous observed object features and the unknown motion parameters. The dynamics of the motion parameters are assumed to be described by a model with unknown parameters that incorporates a bounded uncertainty, and a Lyapunov analysis is provided to prove that the observer yields exponentially convergent estimates that converge to a uniform ultimate bound under a generic persistency of excitation condition. Numerical and experimental results are obtained that demonstrate the robust performance of the current scheme in the presence of model error and measurement noise.     

A non-destructive method to determine stresses in a three-dimensional photoelastic model using a transmission polariscope

The determination of stresses within a loaded three dimensional photoelastic model without cutting it into slices has been the ultimate aim of many investigators. The standard methods using a transmission polariscope do not yield much information. Scattered light methods no doubt enable one to completely determine the state of stress at a point within the body. However, the methods proposed up to now necessitate the use of an arrangement where both the body under test and the sensing unit which picks up the scattered light or both will have to be rotated. This leads to a complicated experimental set-up and increases the possibility of making errors, especially while rotating the model. In the proposed method, most of the information needed to determine the state of stress at a point within the body is obtained using the transmission polariscope set-up. The model and the direction of observation of scattered light are fixed. This allows observations to be made in test models which have at least one flat face without using a liquid with matched refractive index and increases the accuracy of measurements. The method is an almost purely transmission polariscope type of method and where space permits tests can be done using 'live' loading without having to use the stress freezing technique.     

Characterization of kraft pulp delignification using sodium dithionite as bleaching agent

Abstract

The delignification of kraft pulp with sodium dithionite was studied to remove lignin content in the pulp. The sodium dithionite dissolves the chromophoric groups and residual lignin present in the pulp. The increase in dosage of sodium dithionite and reaction temperature of delignification has positive effect on kappa reduction of pulp. X ray diffraction was used to determine the crystallinity index of bleached pulp. The crystallinity increased from 83.3% for unbleached pulp to 86.7% after delignification. Fourier transform infrared spectroscopy shows the reduction in hydrogen bonding in bleached pulp and also the conversion of cellulose I to cellulose II. FT-Raman spectra shows that the fluorescence observed in the spectra of unbleached pulp reduced significantly in comparison to the spectra of bleached pulp resulting in removal of residual lignin and chromophoric groups present in the pulp. Scanning electron imaging shows the smoothening of fiber surface after bleaching. The delignification reaction followed first-order kinetics and activation energy is 33.57kJ/mol.