Matrix Crack Detection in Composite Plate with Spatially Random Material Properties using Fractal Dimension

Fractal dimension based damage detection method is investigated for a composite plate with random material properties. Composite material shows spatially varying random material properties because of complex manufacturing processes. Matrix cracks are considered as damage in the composite plate. Such cracks are often seen as the initial damage mechanism in composites under fatigue loading and also occur due to low velocity impact. Static deflection of the cantilevered composite plate with uniform loading is calculated using the finite element method. Damage detection is carried out based on sliding window fractal dimension operator using the static deflection. Two dimensional homogeneous Gaussian random field is generated using Karhunen-Loeve (KL) expansion to represent the spatial variation of composite material property. The robustness of fractal dimension based damage detection method is demonstrated considering the composite material properties as a two dimensional random field.     

Analysis of competition and market power in the wholesale electricity market in India

The electricity reforms were initiated in India with the objective of promoting competition in the electricity market. In order to promote competition, the Electricity Act 2003 was enacted and various policy initiatives were taken by the Government of India. Central Electricity Regulatory Commission (CERC) also facilitated competition through the regulatory framework of availability based tariff, Indian Electricity Grid Code, open access in inter-state transmission, inter-state trading and power exchanges. Despite these initiatives, electricity prices increased in the Wholesale Electricity Market in India (WEMI). This paper analyses the market structure and competitiveness in the WEMI. There are, of course, various potential reasons for the rise in the electricity price. This paper seeks to investigate, if market power was one of the reasons for increase in market prices. Concentration ratio, Herfindahl–Hirschman index, Supply Margin Assessment, and Residual Supply Index have been used to measure market power. This paper also uses the price–cost mark-up to examine, if exercise of market power led to higher margins. The analysis suggests that market power of firms may be part of the reason for the increase in electricity prices in WEMI. The study suggests various measures to increase competition in the WEMI.     

Studying single nanocrystals under high pressure using an x-ray nanoprobe

In this report, we demonstrate the feasibility of applying a 250-nm focused x-ray beam to study a single crystalline NbSe(3) nanobelt under high-pressure conditions in a diamond anvil cell. With such a small probe, we not only resolved the distribution and morphology of each individual nanobelt in the x-ray fluorescence maps but also obtained the diffraction patterns from individual crystalline nanobelts with thicknesses of less than 50 nm. Single crystalline diffraction measurements on NbSe(3) nanobelts were performed at pressures up to 20 GPa.     

One dimensional nonlocal integro-differential model & gradient elasticity model : Approximate solutions and size effects

In the present work, the close similarity that exists between Mindlin’s strain gradient elasticity and Eringens nonlocal integro-differential model is explored. A relation between length scales of nonlocal-differential model and gradient elasticity model has been arrived. Further, a relation has also been arrived between the standard and nonstandard boundary conditions in both the cases. C⁰-based finite element methods (FEMs) are extensively used for the implementation of integro-differential equations. This results in standard diagonally dominant global stiffness matrix with off diagonal elements occupied largely by the kernel values evaluated at various locations. The global stiffness matrix is enriched in this process by nonzero off diagonal terms and helps in incorporation of the nonlocal effect, there by accounting the long-range interactions. In this case, the diagonally dominant stiffness matrix has a band width equal to influence domain of basis function. In such cases, a very fine discretization with larger number of degrees of freedom is required to predict nonlocal effect, thereby making it computationally expensive. In the numerical examples, both nonlocal-differential and gradient elasticity model are considered to predict the size effect of tensile bar example. The solutions to integro-differential equations obtained by using various higher-order approximations are compared. Lagrangian, Bèzier and B-Spline approximations are considered for the analysis. It has been shown that such higher-order approximations have higher inter-element continuity there by increasing the band width and the nonlocal character of the stiffness matrix. The effect of considering the higher-order and higher-continuous approximation on computational effort is made. In conclusion, both the models predict size effect for one-dimensional example. Further, the higher-continuous approximation results in less computational effort for nonlocal-differential model.     

Conjugation of curcumin with PVP capped gold nanoparticles for improving bioavailability

Curcumin, a natural polyphenolic compound, has astounding therapeutic applications but lacks in bioavailability mainly due to its poor solubility in water. Polyvinyl pyrrolidone (PVP) which is a proven drug carrier has been used to facilitate the conjugation of curcumin with gold nanoparticles and to improve the solubility of curcumin in water. In this conjugate diaryl heptanoid chromophore group of curcumin which is a much needed group in biomedical applications remains intact as observed from FTIR and UV–vis spectroscopy analysis. The work shows good promise for such conjugates as therapeutic-cum-imaging materials in biomedical field.     

Spatially resolved characterization of cellulose nanocrystal-polypropylene composite by confocal Raman microscopy

Raman spectroscopy was used to analyze cellulose nanocrystal (CNC) -polypropylene (PP) composites and to investigate the spatial distribution of CNCs in extruded composite filaments. Three composites were made from two forms of nanocellulose (CNCs from wood pulp and the nano-scale fraction of microcrystalline cellulose) and two of the three composites investigated used maleated PP as a coupling agent. Raman maps, based on cellulose and PP bands at 1098 and 1460 cm(-1), respectively, obtained at 1 μm spatial resolution showed that the CNCs were aggregated to various degrees in the PP matrix. Of the three composites analyzed, two showed clear existence of phase-separated regions: Raman images with strong PP and absent/weak cellulose or vice versa. For the third composite, the situation was slightly improved but a clear transition interface between the PP-abundant and CNC-abundant regions was observed, indicating that the CNC remained poorly dispersed. The spectroscopic approach to investigating spatial distribution of the composite components was helpful in evaluating CNC dispersion in the composite at the microscopic level, which helped explain the relatively modest reinforcement of PP by the CNCs.     

Fiber-optic miniature sensor for in situ temperature monitoring of curing composite material

This study proposes a fiber-optic temperature sensor with a single-mode fiber tip covered with a thermo-sensitive polymer resin. The temperature is sensed by measuring the Fresnel reflection from the optical fiber/polymer interface. Because the thermo-optic coefficients differ between the optical fiber and the polymer, the in situ temperature can be measured even in curing composite materials. In initial experiments, the proposed sensor successfully measured and recovered the temperature information. The measured sensor data were linearly correlated, with an R² exceeding 0.99. The standard deviation in the long-term measurements of constant temperature was 2.6%. The durability and stability of the sensor head material in long-term operation was validated by Fourier transform infrared spectroscopy and X-ray diffraction analysis. In further experiments, the suggested miniature temperature sensor obtained the internal temperatures of curing composite material over a wide range (30–110 °C).     

Sustained release microspheres of diclofenac sodium using PEGylated rosin derivatives

The PEGylated derivatives of rosin-PD-1 and PD-2 synthesized and characterized earlier (Nande et al., 2006) were investigated as potential materials for sustained release microsphere prepared by emulsion solvent evaporation method using diclofenac sodium (DCS) as model drug. All the microspheres exhibited smooth surfaces intercepted by pores; their sizes (d(90)) ranged between 11-24 microm. The entrapment efficiency (< 80%) of the microspheres increased proportionally with derivative concentration. Presence of solvent like isopropyl alcohol or dichloromethane rendered the microspheres with large sizes but with reduced drug entrapment. Microspheres with small size were obtained at an optimum viscosity of liquid paraffin; any change lead to increase in the particle size. Magnesium stearate was found to be most suitable detackifier in the present system. The drug release was directly related to the particle size--small sized microspheres released drug at a faster rate. The dissolution data complied with Higuchi equation while the mechanism of drug release was Fickian diffusion (n approximately 0.5). Controlled inhibition of edema, as tested by hind paw edema method, was observed for 10 h when the microspheres were administered intraperitoneally. The present study found the derivatives as promising materials for preparing microspheres for sustained delivery of DCS.     

Removal of Cr(VI) from aqueous solutions using pre-consumer processing agricultural waste: a case study of rice husk

This paper reports the feasibility of using pre-consumer processing agricultural waste to remove Cr(VI) from synthetic wastewater under different experimental conditions. For this, rice husk, has been used after pre-treatments (boiling and formaldehyde treatment). Effect of various process parameters, namely, pH, adsorbent dose, initial chromium concentration and contact time has been studied in batch systems. The removal of chromium was dependent on the physico-chemical characteristics of the adsorbent, adsorbate concentration and other studied process parameters. Maximum metal removal was observed at pH 2.0. The efficiencies of boiled and formaldehyde treated rice husk for Cr(VI) removal were 71.0% and 76.5% respectively for dilute solutions at 20gl(-1) adsorbent dose. The experimental data were analyzed using Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm models. It was found that Freundlich and D-R models fitted well. The results revealed that the hexavalent chromium is considerably adsorbed on rice husk and it could be an economical method for the removal of hexavalent chromium from aqueous systems. FTIR and SEM were recorded, before and after adsorption, to explore number and position of the functional groups available for Cr(VI) binding on to studied adsorbents and changes in adsorbent surface morphology.