Role of ceria in CO2 adsorption on NaZSM-5 synthesized using rice husk ash

Ceria (3, 5, 7, 11, 19 wt%) impregnated NaZSM-5 was synthesized and studied for adsorption of CO₂. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), CO₂-temperature programmed desorption (CO₂-TPD) and Brunauer–Emmett–Teller (BET) techniques. The heat of the reaction (ΔH_r) derived from differential scanning calorimetry (DSC) analysis was 490 Btu/lb. XRD analysis showed a decrease in the intensity of patterns with the increase in the ceria loading but crystallization of ceria to larger size was clearly evident for 11 and 19% loading. The surface area decreased for 3 and 5% loading, but increased for 7, 11 and 19% loading illustrating difference in dispersion. The maximum adsorption capacity of CeO₂(5%)/NaZSM-5 was 130 mg/g of sorbent. Extraction of silica from the agricultural waste, rice husk, and its use in the zeolite synthesis was an advantage in this study. Hence, from the study it was concluded that ceria impregnated NaZSM-5 could be treated as a novel material for CO₂ adsorption, as they were regenerable and recyclable. This study can also be applied to all other zeolites.     

Study of shrinkage stresses for drying of brick as a conjugate problem

Drying induced shrinkage stresses of a two‐dimensional rectangular brick of aspect ratio 2 is studied numerically. The drying of brick is analysed as a conjugate problem. The conservation equations for the solid are obtained using continuum approach and the Navier–Stokes equations have been solved for the flow field. An elastic model has been used to calculate the shrinkage stresses. The present unified model predicts the stress concentration at the leading edge where it is expected to be maximum due to large shrinkage. Copyright © 2000 John Wiley & Sons, Ltd.     

Thermal Performance Simulation of a Heat Pump Assisted Solar Desalination System for Kazakhstan Climatic Conditions

ABSTRACT

A numerical model has been proposed in this research work for predicting the energy performance of a heat pump assisted regenerative solar still using phase change heat storage materials such as paraffin wax and hydrate salt. The numerical model is based on energy and mass balance. The performance was simulated for Fort Sherchenko town in Kazakhstan. The performance comparison between the conventional solar still and heat pump assisted regenerative solar still with and without phase change materials are presented. Moreover, the influence of two different phase change materials on thermal performance of a heat pump assisted regenerative solar still are described. The numerical simulation results showed that heat pump assisted regenerative solar still is more energy efficient and produces better productivity when compared to the conventional simple solar still. The use of hydrate salt phase change heat storage material was found to be a good option for enhancing the performance of a heat pump assisted regenerative solar still.     

Purification, characterization, and antifungal activity of chitinase from Fusarium chlamydosporum, a mycoparasite to groundnut rust, Puccinia arachidis

Chitinase (EC 3.2.1.14) was isolated from the culture filtrate of Fusarium chlamydosporum and purified by ion-exchange chromatography and gel filtration. The molecular mass of purified chitinase was 40 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Chitinase was optimally active at a pH of 5 and stable from pH 4 to 6 and up to 40 degrees C. Among the metals and inhibitors tested, mercuric chloride completely inhibited the enzyme activity. The activity of chitinase was high on colloidal and pure chitin. The purified chitinase inhibited the germination of uredospores of Puccinia arachidis and also lysed the walls of uredospores and germ tubes. The results from these experiments indicated that chitinase of F. chlamydosporum plays an important role in the biocontrol of groundnut rust.     

Fault-tolerant spacecraft attitude control system

Spacecraft perform a variety of useful tasks in our day-to-day life. These are such that spacecraft need to function properly without interruptions for 7 to 15 years in space without any maintenance. Though most spacecraft have redundant systems to serve as back-ups in case of failures, they greatly depend on human assistance through ground stations for failure analysis, remedial actions and redundancy management, resulting in itnerruption in services rendered. There is, therefore, need for a fault-tolerant system that functions despite failures and takes remedial action, without human assistance/intervention, autonomously on board the spacecraft. Commonly used techniques for fault-tolerance in computers cannot be directly used for fault-tolerance in sensors and actuators of a closed loop control system. Further, for space applications fault-tolerance needs to be achieved without much penalty in weight and computational requirements. This paper describes briefly the attitude control system (acs) of a spacecraft and highlights the essential features of a fault-tolerant control system. Schemes for fault tolerance in sensors and actuators are presented with an analysis on various failure modes and their effects. Newly developed fault-detection, identification and reconfiguration (fdir) algorithms for various elements ofacs are described in detail. Also an optimum symmetrically skewed configuration for the attitude reference system using dynamically tuned gyros is developed. Some of the schemes have already been used in Indian Spacecraft. As future Indian space missions will directly cater to various applications on an operational basis, the ultimate objective is to have a totally fault-tolerant ‘intelligent’ autonomous spacecraft.     

The attitude control system of the satellite for earth observation ‘ Bhaskara ’

The satellite for earth observation (Bhaskara) launched on 7 June 1979 has two TV cameras and a passive microwave radiometer for earth resources survey and meteorological studies respectively. As it had to be a minimally modified version of the earlier spin-stabilised satelliteAryabhata, it is configured as a spin-stabilised satellite, with a spin rate of between 6 to 11 rev/min and a spin axis perpendicular to the orbital plane within 3°. The cold gas system ofAryabhata was modified to provide a low and controlled thrust for spin-up and spin-axis orientation operations. Two horizon-crossing sensors are used for automatic spin-axis control and attitude determination on ground. This paper presents a report on the system evolution, design, simulation and on-orbit performance ofBhaskara.     

Time-dependent fundamental solutions for homogeneous diffusion problems

This paper describes the applications of the method of fundamental solutions (MFS) for 1-, 2- and 3-D diffusion equations. The time-dependent fundamental solutions for diffusion equations are used directly to obtain the solution as a linear combination of the fundamental solution of the diffusion operator. The proposed scheme is free from the conventionally used Laplace transform or the finite difference scheme to deal with the time derivative of the governing equation. By properly placing the field points and the source points at a given time level, the solution is advanced in time until steady state solutions are reached. Test results obtained for 1-, 2- and 3-D diffusion problems show good comparisons with the analytical solutions and some with the MFS based on the modified Helmholtz fundamental solutions, thus the demonstration present numerical scheme of MFS with the space–time unification has been demonstrated as a promising mesh-free numerical tool to solve homogeneous diffusion problem.     

High‐Performance Long‐Term‐Stable Dopant‐Free Perovskite Solar Cells and Additive‐Free Organic Solar Cells by Employing Newly Designed Multirole π‐Conjugated Polymers

Perovskite solar cells (PSCs) and organic solar cells (OSCs) are promising renewable light‐harvesting technologies with high performance, but the utilization of hazardous dopants and high boiling additives is harmful to all forms of life and the environment. Herein, new multirole π‐conjugated polymers (P1–P3) are developed via a rational design approach through theoretical hindsight, further successfully subjecting them into dopant‐free PSCs as hole‐transporting materials and additive‐free OSCs as photoactive donors, respectively. Especially, P3‐based PSCs and OSCs not only show high power conversion efficiencies of 17.28% and 8.26%, but also display an excellent ambient stability up to 30 d (for PSCs only), owing to their inherent superior optoelectronic properties in their pristine form. Overall, the rational approach promises to support the development of environmentally and economically sustainable PSCs and OSCs.     

Ternary nanocomposite designed by MWCNT backbone PPy/Pd for efficient catalytic approach toward reduction and oxidation reactions

An induced active palladium nanoparticle (Pd NP) on multiwall carbon nanotube with polypyrrole matrix (MWCNT/PPy/Pd) was prepared and their physiochemical properties were investigated. The XPS (X-ray photoelectron spectroscopy) analysis showed the important amine and imine linkage at 400.3?eV and 398.8?eV for the interaction of the polymer matrix. FTIR spectroscopy proved the polypyrrole stretching frequencies and palladium nitrogen interaction (Pd-N at 1618?cm^?1). TGA-DSC analysis showed that 51% of polymer composite remained up to 1000?°C. The developed nanocomposite (NC) catalytic ability was tested in p-nitrophenol reduction and methanol oxidation studies. The kinetic rate constant (k) was 0.193?min^?1 and NC exhibited good reusability up to 10 cycles for p-nitrophenol reduction. The electrochemical measurements indicate that MWCNT/PPy/Pd has a significantly high active surface area (3.13?cm^?2), low onset potential and high current density. MWCNT/PPy/Pd ternary NC is a capable candidate for both electro-oxidation of methanol and a reduction of 4-nitrophenol.     

Interlaminar shear stresses in laminated composite plates under thermal and mechanical loading

The combined effects of thermal and mechanical loadings on the distribution of interlaminar shear stresses in composite laminated thin and moderately thick composite plates are investigated numerically using the commercially available software package MSC NASTRAN/PATRAN. The validity of the present finite element analysis is demonstrated by comparing the interlaminar shear stresses evaluated using the experimental measurement. Various parametric studies are also performed to investigate the effect of stacking sequences, length to thickness ratio, and boundary conditions on the interlaminar shear stresses with identical mechanical and thermal loadings. It is observed that the effect of thermal environment on the interlaminar shear stresses in carbon-epoxy fiber-reinforced composite laminated plates are much higher in asymmetric cross-ply laminate and anti-symmetric laminate compared to symmetric cross-ply laminate and unidirectional laminate under identical loadings and boundary conditions.